阅读说明：本技术 锁相环电路 (Phase-locked loop circuit ) 是由 有坂直也 藤原徹哉 江藤慎一郎 于 2019-02-15 设计创作，主要内容包括：本技术涉及能够降低功耗的锁相环电路。锁相环电路包括：SAR-ADC,包括两个电容器,并且输出从两个电容器生成的电压之间的比较结果；电流源,用电流对两个电容器充电；第一开关,布置在两个电容器中的一个电容器与电流源之间,并且被提供有具有参考频率的第一时钟与具有高于第一时钟的频率的第二时钟之间的相位差；以及第二开关,布置在两个电容器中的另一电容器与电流源之间,并且被提供有第二时钟。本公开例如可以应用于无线通信设备。(The present technology relates to a phase-locked loop circuit capable of reducing power consumption. The phase-locked loop circuit includes: a SAR-ADC including two capacitors and outputting a comparison result between voltages generated from the two capacitors; a current source for charging the two capacitors with a current; a first switch arranged between one of the two capacitors and the current source and provided with a phase difference between a first clock having a reference frequency and a second clock having a frequency higher than the first clock; and a second switch arranged between the other of the two capacitors and the current source and supplied with a second clock. The present disclosure may be applied to, for example, a wireless communication device.)

1. A phase-locked loop circuit comprising:

a SAR-ADC including two capacitors and outputting a comparison result between voltages generated from the two capacitors;

a current source for charging the two capacitors with a current;

a first switch arranged between one of the two capacitors and the current source and supplied with a phase difference between a first clock having a reference frequency and a second clock having a frequency higher than the first clock; and

a second switch arranged between the other of the two capacitors and the current source and supplied with the second clock.

2. The phase-locked loop circuit of claim 1,

the current source charges the one capacitor with a current for a time corresponding to the phase difference based on the operation of the first switch, and charges the other capacitor with a current for a time corresponding to the second clock based on the operation of the second switch.

3. The phase-locked loop circuit of claim 2,

the time corresponding to the second clock is a time greater than one clock cycle.

4. The phase-locked loop circuit of claim 2,

the one capacitor generates a voltage corresponding to the phase difference, and the other capacitor generates a voltage corresponding to the second clock.

5. The phase-locked loop circuit of claim 4,

the capacitance ratio between the one capacitor and the other capacitor is 1: 1.

6. The phase-locked loop circuit of claim 4,

the current sources include a first current source that charges the one capacitor with a current and a second current source that charges the other capacitor with a current.

7. The phase-locked loop circuit of claim 6,

the capacitance of the other capacitor is N times the capacitance of the one capacitor, and

the second current source charges the further capacitor with a current that is N times the current of the first current source.

Technical Field

The present technology relates to a phase-locked loop circuit, and more particularly, to a phase-locked loop circuit that allows power consumption to be reduced.

Background

For the coming IoT era, power reduction of LSIs is required. The power consumption of the local oscillator is a large proportion of the power consumption of the analog block mounted on the LSI. The local oscillator includes a PLL circuit. Recently, all-digital pll (adpll) circuits have sometimes been used.

The ADPLL circuit generates a DCO frequency from a digital set frequency data Frequency Command Word (FCW) and an external reference frequency to satisfy a relationship of the DCO frequency FCW × the reference frequency. To match the ratio between the DCO frequency and the reference frequency to the FCW, the ADPLL includes: a counter circuit that detects an integer phase difference between the DCO frequency signal Fdco and the reference frequency signal Fref; and a time-to-digital converter (TDC) circuit that detects fractional phase (fractional phase) differences.

The counter circuit detects an integer phase difference by counting how many cycles of Fdco are input in one cycle of Fref, and thus must always operate in one cycle of Fref. On the other hand, the TDC circuit only needs to detect the phase difference between the edges of Fref and Fdco, and therefore does not need to continue operating all the way through one cycle of Fref, and can operate intermittently. Intermittent operation reduces the average current consumption per hour and therefore allows power reduction.

The TDC circuit delays Fdco in several inverter circuit stages and captures a rising edge of Fref with a latch circuit, thereby detecting a phase difference. This configuration is simple but difficult to operate at low power because a large number of inverter circuits need to be operated to generate a delay when the phase difference between Fref and Fdco is large, resulting in an increase in current consumption.

Therefore, non-patent document 1 proposes a TDC circuit designed to improve increased power consumption. The TDC circuit generates a signal of a phase difference between Fref and Fdco in the Phase Detector (PD), and charges a capacitor C1 with a current from a Charge Pump (CP) during a time of the signal of the phase difference to obtain electricityPressure V_F。

And, when obtaining the voltage V_FThereafter, the TDC circuit charges capacitor C2 with current from CP to generate voltage V_RAMPAnd the number of pulses of Fdco is counted (count number: n) up to the voltage V_FAnd voltage V_RAMPCrossing in a single slope ADC (SS-ADC). Capacitor C1 and capacitor C2 are 1: N. Thus, the voltage V_FAnd voltage V_RAMPThe slope of (A) is N: 1. Thus, N/N is the AD conversion value and is the phase difference between Fref and Fdco.

Reference list

Non-patent document

Non-patent document 1: somnath Kundi, Bongjin Kim, Chris H.Kim, "19.2A 0.2-1.45GHzSubsampling Fractional-N All-Digital MDLL with Zero-Offset Aperture PD-base spread screening and In-site Timing Mismatch Detection", 2016 EEEEInternational Solid-State Circuits reference, February3,2016, [ search on line ] [ 1/25 th 2018 ], Internet < URL: http:// www.ee.umn.edu/groups/VLSI research/pages/2016/ISSCC 16_ M.DLL.

Disclosure of Invention

Technical problem to be solved by the invention

However, in the proposal of non-patent document 1, when the phase difference between Fref and Fdco is large, the voltage V is obtained_FAnd voltage V_RAMPThe CP needs to continue operating with several Fdco clocks before. Therefore, during one cycle of Fref, the intermittent ratio becomes low, making it difficult to sufficiently reduce the power.

The present technology has been made in view of such a situation, and enables reduction in power consumption.

Solution to the problem

A phase-locked loop circuit according to an aspect of the present technology includes: a SAR-ADC including two capacitors and outputting a comparison result between voltages generated from the two capacitors; a current source for charging the two capacitors with a current; a first switch arranged between one of the two capacitors and the current source and provided with a phase difference between a first clock of a reference frequency and a second clock having a frequency higher than the first clock; and a second switch arranged between the other of the two capacitors and the current source and provided with a second clock.

One aspect in accordance with the present technique includes: a SAR-ADC including two capacitors and outputting a comparison result between voltages generated from the two capacitors; a current source for charging the two capacitors with a current; a first switch arranged between one of the two capacitors and the current source and provided with a phase difference between a first clock of a reference frequency and a second clock having a frequency higher than the first clock; and a second switch arranged between the other of the two capacitors and the current source and provided with a second clock.

Effects of the invention

According to the present technology, power consumption can be reduced.

It should be noted that the effects described in this specification are merely examples. In this specification, the effects of the present technology are not limited to the described effects, and additional effects may be included.

Drawings

Fig. 1 is a block diagram showing a configuration example of an ADPLL circuit to which the present technique is applied.

Fig. 2 is a diagram showing an operation of the ADPLL circuit.

Fig. 3 is a diagram showing a conventional TDC circuit for comparison with the present technology.

Fig. 4 is a diagram showing how the fractional phase difference between the reference frequency signal Fref and the DCO frequency signal Fdco is determined.

Fig. 5 is a diagram showing a configuration example of a conventional TDC circuit in the case where N is 70 and N is 69.

Fig. 6 is a diagram illustrating an operation of the TDC circuit in fig. 5.

Fig. 7 is a circuit diagram showing a configuration example of the TDC circuit in fig. 1.

Fig. 8 is a diagram illustrating an operation of the TDC circuit in fig. 7.

Fig. 9 is a circuit diagram showing a first variation of the TDC circuit in fig. 7.

Fig. 10 is a diagram illustrating an operation of the TDC circuit in fig. 9.

Fig. 11 is a circuit diagram showing a second variation of the TDC circuit in fig. 7.

Fig. 12 is a diagram illustrating an operation of the TDC circuit in fig. 11.

Fig. 13 is a block diagram showing a configuration example of a wireless communication device including an ADPLL circuit.

Detailed Description

Hereinafter, modes for carrying out the present disclosure (hereinafter referred to as "embodiments") will be described. The description is made in the following order.

1. First embodiment (ADPLL circuit)

2. Second embodiment (Wireless communication device)

<1 > first embodiment >

< example of configuration of ADPLL Circuit of the present technology >

Fig. 1 is a block diagram showing a configuration example of an all-digital pll (adpll) circuit as a phase-locked loop to which the present technique is applied.

The ADPLL circuit 1 shown in fig. 1 generates a Digitally Controlled Oscillator (DCO) frequency satisfying a relationship of DCO frequency FCW × reference frequency from a digitally set frequency data Frequency Command Word (FCW) and an external reference frequency. The DCO frequency is a frequency higher than the reference frequency. The digital set frequency data FCW is data for setting the DCO frequency, and is supplied from a control unit of the apparatus including the ADPLL circuit 1 and the like.

The ADPLL circuit 1 includes a counter circuit 11, a time-to-digital counter (TDC) circuit 12, a digital operation circuit 13, and a Voltage Controlled Oscillator (VCO) 14.

The reference frequency signal Fref is supplied to the counter circuit 11 and the TDC circuit 12. The digital set frequency data FCW is supplied to the digital arithmetic circuit 13.

The counter circuit 11 detects an integer phase difference between the externally supplied reference frequency signal Fref and the DCO frequency signal Fdco supplied from the VCO 14, and outputs a signal representing the detected integer phase difference to the digital operation circuit 13.

The TDC circuit 12 detects a fractional phase difference between the externally supplied reference frequency signal Fref and the DCO frequency signal Fdco supplied from the VCO 14, and outputs a signal representing the detected fractional phase difference to the digital operation circuit 13.

The digital operation circuit 13 compares a signal indicating the phase difference supplied from the counter circuit 11 and the TDC circuit 12 with phase information obtained by time integration of the digital set frequency data FCW, and outputs the comparison result to the VCO 14 through a digital filter.

The VCO 14 outputs a signal of the oscillation frequency according to the comparison result supplied from the digital operation circuit 13 to a subsequent stage (not shown) as a DCO frequency signal Fdco. The DCO frequency signal Fdco is fed back to the counter circuit 11 and the TDC circuit 12.

< example of operation of ADPLL Circuit >

Fig. 2 is a diagram illustrating an operation of the ADPLL circuit.

Fig. 2 shows an example of the numeric set frequency data FCW 3.2. The signal waveform of the reference frequency signal Fref, the signal waveform of the DCO frequency signal Fdco, the integer phase detected in the counter circuit 11, and the fractional phase detected in the TDC circuit 12 are shown in order from top to bottom. Further, it is shown that the phase comparison is performed in the digital operation circuit 13 for the value of integer phase + fractional phase and the value of integer multiple of the digitally set frequency data FCW.

Near the first rising edge of the reference frequency signal Fref, the integer phase of the DCO frequency signal Fdco is 0 and the fractional phase is also 0. Therefore, the digital operation circuit 13 performs phase comparison between the integer phase + fractional phase "0" and the integer multiple "0" of the digital set frequency data FCW.

Near the second rising edge of the reference frequency signal Fref, the integer phase of the DCO frequency signal Fdco is 3 and the fractional phase is 0.2. Therefore, the digital operation circuit 13 performs phase comparison between the integer phase + fractional phase "3.2" and the integer multiple "3.2" of the digital set frequency data FCW.

Near the third rising edge of the reference frequency signal Fref, the integer phase of the DCO frequency signal Fdco is 6 and the fractional phase is 0.4. Therefore, the digital operation circuit 13 performs phase comparison between the integer phase + fractional phase "6.4" and the integer multiple "6.4" of the digital set frequency data FCW.

Note that the processing for the fourth rising edge and the subsequent rising edge is performed in a similar manner, and thus the description is not repeated.

< description of conventional example to compare with the present technology >

Fig. 3 is a diagram showing a conventional TDC circuit in comparison with the present technology.

The TDC circuit shown in fig. 3 includes a phase-locked loop (PD)21, a Charge Pump (CP)22, and a single-slope ADC (SS-ADC) 23.

PD 21 generates a phase difference signal phi between a reference frequency signal Fref and a DCO frequency signal Fdco_F(0 to 2 π).

In providing a phase difference signal phi_FMeanwhile, the CP 22 charges an internally provided capacitor C1 (not shown) with a current. The voltage V of the phase difference information voltage to be generated in the capacitor C1 due to the current charged in the CP 22_FOutput to SS-ADC 23.

The SS-ADC23 includes a capacitor C2(C1: C2 ═ 1: N (N ≧ 2)), a current source 31, a comparator 32, and an integrator 33. Voltage V to be output from capacitor C1_FIs provided to comparator 32.

The current source 31 charges the capacitor C2 with current. The voltage V of the period information voltage to be generated in the capacitor C2 due to the current charged by the current source 31_RAMPOutput to the comparator 32.

The comparator 32 converts the voltage V_FAnd voltage V_RAMPThe comparison is performed, and the comparison result is output to the integrator 33.

The integrator 33 counts the number of pulses of the DCO frequency signal Fdco (count number: n (n ≧ 1)) up to the voltage V_FAnd voltage V_RAMPIntersect and output the operation result D_out。

Since the capacitor C1 and the capacitor C2 are 1: N, the voltage V_FAnd voltage V_RAMPThe slope of (A) is N: 1. N/N is AD conversion value and is the reference frequency signal Fref and the DCO frequency signalPhase difference between the numbers Fdco.

FIG. 3 shows the phase difference signal Φ on the lower side of the arrangement diagram_FSignal waveform of (3), signal waveform of DCO frequency signal Fdco, signal waveform of reference frequency signal Fref, and voltage V generated in capacitor C1_FAnd the voltage V generated in the capacitor C2_RAMP(slope ratio N: 1).

The operation of the TDC circuit will be described. The PD 21 generates the phase difference signal Φ in a period between time t2 of the rising edge of the reference frequency signal Fref and time t3 of the subsequent rising edge of the DCO frequency signal Fdco_FAnd phase difference signal phi_FAnd output to CP 22.

In providing a phase difference signal phi_FWhile (i.e. at the phase difference signal phi)_FBetween time t12 of the rising edge and time t13 of the subsequent rising edge of the DCO frequency signal Fdco), the CP 22 charges the capacitor C1 with current, so that a voltage V is generated in the capacitor C1_F。

After waiting for one period after the capacitor C1 is charged with the current, at time t14 of the rising edge of the DCO frequency signal Fdco, the capacitor C2 is charged with the current from the current source 31, so that the voltage V is generated in the capacitor C2_RAMP。

The integrator 33 counts the number of pulses of the DCO frequency signal Fdco (2 π in the case of FIG. 1) (count number: n (n ≧ 1)) up to the voltage V_RAMPVoltage V in and comparator 32_FAnd (4) matching. When the voltage V is_RAMPAnd voltage V_FUpon matching, at time t32 of the rising edge of the DCO frequency signal Fdco, the charging of the capacitor C2 with the current from the current source 31 is completed, and the integrator 33 completes counting and outputs the operation result D_out。

Fig. 4 is a diagram showing how the fractional phase difference between the reference frequency signal Fref and the DCO frequency signal Fdco is determined.

The example of fig. 4 shows the case where the slope ratio is 4: 1.

The upper row shows the phase difference signal phi_FIs pi/2, the DCO frequency signal Fdco is 2 pi and the result of the operationD_outIs the case at 1. That is, a value 0.25 obtained by dividing one count in the DCO frequency signal Fdco by 4 is the phase difference signal Φ_FThe value of (c).

The middle row shows the phase difference signal phi_FIs pi, the DCO frequency signal Fdco is 2 pi, and the operation result D_outIs the example at 2. That is, a value 0.5 obtained by dividing two counts in the DCO frequency signal Fdco by 4 is the phase difference signal Φ_FThe value of (c).

The lower row shows the phase difference signal phi_FIs 2 pi, the DCO frequency signal Fdco is 2 pi, and the operation result D_outIs the example at 4. That is, a value 1 obtained by dividing four counts in the DCO frequency signal Fdco by 4 is the phase difference signal Φ_FThe value of (c).

Fig. 5 is a diagram showing a configuration example of a conventional TDC circuit when the ratio of two capacitors is 1: N (N-70) and the count number of integrators is N-69.

The TDC circuit shown in fig. 5 includes a CP 22, an SS-ADC23, and a normalization unit 51. In the example of fig. 5, the range of the bottom arrow indicates the configuration of the components, and the PD 21 is omitted.

CP 22 includes a current source 31, a switch 41, and a capacitor C_F。

The SS-ADC23 includes a current source 31, a switch 42, and a capacitor C_RComparator 32, latch circuit 43, integrator 33, latch circuit 44, latch circuit 45, and arithmetic unit 46.

The current source 31 includes a transistor M_p1And M_p2And is shared by CP 22 and SS-ADC23 by means of the switching of switches 41 and 42.

In providing a phase difference signal phi_FAt the same time, the switch 41 is turned on and the capacitor C is charged with current from the current source 31_FAnd (6) charging. Will be in the capacitor C_FVoltage V generated in_FIs provided to comparator 32.

Further, while an enable signal (enable signal) EN is supplied from the latch circuit 43, the switch 42 is turned on, and the capacitor C is supplied with a current from the current source 31_R(C_F:C_R1:70) charging. Will be in the capacitor C_RVoltage V generated in_RAMPIs provided to comparator 32.

The comparator 32 converts the voltage V_FAnd voltage V_RAMPMake a comparison and if the voltage V is_FAnd voltage V_RAMPAnd matches, the comparator 32 outputs a stop signal to the latch circuit 43.

When the latch circuit 43 is set at the phase difference signal Φ_FWhen the supply of the start signal is completed, the latch circuit 43 outputs the enable signal EN to the switch 42.

The integrator 33 counts the number of pulses of the DCO frequency signal Fdco, and outputs the counted number to the latch circuit 44 and the latch circuit 45.

When the latch circuit 44 is set at the phase difference signal phi_FThe latch circuit 44 holds the count number at the time of a start signal output at the end of supply (14 in fig. 6 described later), and outputs the count number to the arithmetic unit 46 at a predetermined time.

When the latch circuit 45 is provided with a stop signal output from the comparator 32 (83 in fig. 6 described later), the latch circuit 45 holds the count number, and outputs the count number to the arithmetic unit 46 at a predetermined time.

The operation unit 46 calculates the operation result D of the difference between the value supplied from the latch circuit 44 and the value supplied from the latch circuit 45_outOutput to the normalization unit 51.

The normalization unit 51 comprises a multiplier 47. The multiplier 47 will pass the operation result D supplied from the operation unit 46_outNormalized result D obtained by multiplying 1/70_FAnd outputting to a subsequent stage.

Fig. 6 is a diagram illustrating an operation of the TDC circuit in fig. 5.

FIG. 6 shows the signal waveform of the reference frequency signal Fref and the phase difference signal Φ in the order from the top_FSignal waveform of (2), signal waveform of enable signal EN, in capacitor C_FVoltage V generated in_FAnd in the capacitor C_RVoltage V generated in_RAMP(slope ratio 1: 70). Note that due to the influence of errors and the likeThe slope shown as a solid line is not linear in nature. However, they are under the same condition, and therefore a linear slope as shown by a dotted line is used when comparing voltages, an error or the like is removed from the linear slope.

The count value of the integrator 33 and the calculation result D are shown below the slope_outValue of (D) and normalization result D_FThe value of (c).

The phase difference signal Φ is provided at time t51 when the rising edge from Fref_FWhile the capacitor C is being supplied with current from the current source 31_FIs charged and in the capacitor C_FIn the generation of a voltage V_F. The integrator 33 counts the number of pulses of the DCO frequency signal Fdco from the start of the DCO frequency signal Fdco, and continues to output the counted number to the latch circuit 44 and the latch circuit 45. The latch circuit 44 holds the count value (14) at time t52 of the rising edge of the enable signal EN by the phase difference signal Φ_FIs caused by a start signal output at the end of the supply.

The comparator 32 converts the voltage V_FAnd voltage V_RAMPComparing and applying a voltage V_FAnd voltage V_RAMPWhen there is a match, a stop signal is output to the latch circuit 45 at time t 61. The latch circuit 45 holds the count value (83) at time t 61.

The operation unit 46 calculates a result D of operation of the difference between the value (14) supplied from the latch circuit 44 and the value (83) supplied from the latch circuit 45_out(69) Output to the normalization unit 51.

The multiplier 47 will pass the operation result D supplied from the operation unit 46_out(69) Normalized result D obtained by multiplying 1/70_F(69/70) output to subsequent stages.

As described above with reference to FIGS. 5 and 6, if the phase difference between the reference frequency signal Fref and the DCO frequency signal Fdco is large, the conventional TDC circuit needs to continuously operate the CP or the current source for several clocks of the DCO frequency signal Fdco to obtain the voltage V_RAMPAnd voltage V_F. Therefore, the intermittent ratio in one period of the reference frequency signal Fref is reduced, thereby preventing sufficient power dropLow.

< TDC Circuit of the present technology >

Fig. 7 is a circuit diagram showing a configuration example of the TDC circuit in fig. 1.

The TDC circuit 12 of fig. 7 includes a current source 111, a PD 112, switches 113-1 and 113-2, and a Successive Approximation (SAR) _ ADC 114 including two capacitors.

Current source 111 charges capacitor 131-1, which is one of the two capacitors of SAR ADC 114, with current via switch 113-1. In addition, current source 111 charges capacitor 131-2, which is the other of the two capacitors of SAR ADC 114, with current via switch 113-2.

The PD 112 includes a flip-flop circuit. The PD 112 generates a phase difference signal phi of the reference frequency signal Fref and the DCO frequency signal Fdco_F. Phase difference signal phi to be generated by the PD 112_FOutput to switch 113-1. Thus, only the phase difference signal Φ is provided_FWhen so, the switch 113-1 is turned on. When the switch 113-1 is turned on, the capacitor 131-1 is charged with a current from the current source 111, and a voltage V is generated in the capacitor 131-1_F。

The DCO frequency signal Fdco is supplied to the switch 113-2 for one cycle (one clock) after the capacitor 131-1 is charged with the current from the current source 111. Thus, during one cycle (one clock) of the DCO frequency signal Fdco, the switch 113-2 is turned on. When the switch 113-2 is turned on, the capacitor 131-2 is charged with a current from the current source 111, and a voltage V is generated in the capacitor 131-2_RAMP。

SAR _ ADC 114 is based on voltage V generated in capacitor 131-1_FWith the voltage V generated in the capacitor 131-2_RAMPAnd outputs the AD conversion result.

SAR ADC 114 includes comparator 121, SAR logic circuit 122, capacitor 131-1, capacitor 131-2, inverter 132-1, and inverter 132-2.

The comparator 121 converts the voltage V_FAnd voltage V_RAMPThe comparison is made and the comparison result (H/L) is output to the SAR logic circuit 122.

The SAR logic circuit 122 performs an operation on the comparison result supplied from the comparator 121, and outputs the operation result to the outside (not shown). SAR logic circuit 122 controls inverters 132-1 and 132-2 to control the H/L of capacitors 131-1 and 131-2.

The capacitance of the capacitor 131-1 is C1, and the capacitance of the capacitor 131-2 is C2(C1: C2 ═ 1: 1).

Inverter 132-1 controls the H/L of capacitor 131-1 based on the control of SAR logic circuit 122. Inverter 132-2 controls the H/L of the capacitance of capacitor 131-2 based on the control of SAR logic circuit 122.

Note that the pair of the capacitor 131-1 and the inverter 132-1 and the pair of the capacitor 131-2 and the inverter 132-2 may be one of a plurality of pairs, respectively. However, the capacitance ratio between the pair of the capacitor 131-1 and the inverter 132-1 and the pair of the capacitor 131-2 and the inverter 132-2 is 1: 1.

< operation of TDC Circuit >

Fig. 8 is a diagram illustrating an operation of the TDC circuit in fig. 7.

FIG. 8 shows, in order from the top, the signal waveform of the reference frequency signal Fref, the signal waveform of the DCO frequency signal Fdco, and the phase difference signal Φ_FThe voltage V generated in the capacitor 131-1(C1)_FAnd the voltage V generated in the capacitor 131-2(C2)_RAMPThe slope of (a).

Providing a phase difference signal Φ at time T1 from a rising edge of the reference frequency signal Fref_FWhen so, the switch 113-1 is turned on. The capacitor 131-1 is charged with a current from the current source 111, and a voltage V is generated in the capacitor 131-1_F. After waiting for one cycle, the DCO frequency signal Fdco is supplied for one cycle from time T3 of the subsequent rising edge of the DCO frequency signal Fdco, so that the switch 113-2 is turned on. Charging the capacitor 131-2 with current from the current source 111 and generating a voltage V in the capacitor 131-2_RAMP。

SAR logic circuit 122 then controls inverters 132-1 and 132-2 from time T5 of the subsequent rising edge to control the H/L of capacitors 131-1 and 131-2. Therefore, after the voltage is once generated, the voltages V are sequentially compared in the comparator 121_FAnd voltage V_RAMPAnd outputs the comparison result, e.g., H, L, H, L, L, H … ….

Note that the voltage V_FAnd voltage V_RAMPThe median of (d) is the common mode input voltage of the comparator (arbitrary).

As described above, in the present technology, the capacitance ratio between the capacitors 131-1 and 131-2 is 1:1, and further, the SAR-ADC is used. Therefore, with respect to obtaining the voltage V corresponding to the AD conversion_RAMPThe overall voltage conventional operation of the current source is sufficient to operate the current source for only one cycle (one clock) of the DCO frequency signal Fdco. Therefore, a high intermittent ratio can be obtained with respect to the period of the reference frequency signal Fref, and the intermittent ratio does not depend on the magnitude of the phase difference between the reference frequency signal Fref and the DCO frequency signal Fdco.

Here, one clock that operates the current source for the DCO frequency signal Fdco has been described, but any number of clocks that lasts no less than one clock may be operated.

On the other hand, the conventional TDC circuits described above with reference to fig. 3 to 5 require more than two clocks to operate the current source for the DCO frequency signal Fdco in order to obtain the voltage V_RAMP. Further, in the conventional TDC circuit, if the phase difference between the reference frequency signal Fref and the DCO frequency signal Fdco is large, the current source is operated to obtain the voltage V_RAMPCan be extended to reduce the intermittent ratio in one cycle of Fref. Thus, the TDC circuit of the present technique is advantageous over conventional TDC circuits in that it can operate at a lower power.

< first modification >

Fig. 9 is a circuit diagram illustrating a first variation of the TDC circuit in fig. 7.

The TDC circuit 12 of fig. 9 differs from the TDC circuit 12 of fig. 7 in that current sources 161-1 and 161-2 are added instead of the current source 111. The other configuration is substantially similar to that of fig. 7, and thus description is omitted.

Current sources 161-1 and 161-2 have a current mirror ratio of 1:1 and charge capacitors 131-1 and 131-2 with current, respectively.

< operation of TDC Circuit >

Fig. 10 is a diagram illustrating an operation of the TDC circuit in fig. 9.

FIG. 10 shows, in order from the top, the signal waveform of the reference frequency signal Fref, the signal waveform of the DCO frequency signal Fdco, and the phase difference signal Φ_FThe voltage V generated in the capacitor 131-1(C1)_FAnd the voltage V generated in the capacitor 131-2(C2)_RAMPThe slope of (a).

Providing a phase difference signal Φ at time T11 from a rising edge of the reference frequency signal Fref_FWhen so, the switch 113-1 is turned on. The capacitor 131-1 is charged with current from the current source 161-1 and a voltage V is generated in the capacitor 131-1_F. Next, the DCO frequency signal Fdco is supplied in one cycle from the time T12 of the rising edge of the DCO frequency signal Fdco, so that the switch 113-2 is turned on. Charging the capacitor 131-2 with current from the current source 161-2 and generating a voltage V in the capacitor 131-2_RAMP。

After the voltage is generated, the operation of the TDC circuit is substantially similar to that of the example of fig. 8, and thus the description thereof will be omitted.

As described above, the TDC circuit of FIG. 9 can simultaneously perform the voltage V_FAnd voltage V_RAMPWithout waiting for the voltage V_RAMPThe charging current of (a) lasts for one cycle, and thus the AD conversion result can be obtained faster than the TDC circuit of fig. 7.

< second modification >

Fig. 11 is a circuit diagram illustrating a second variation of the TDC circuit in fig. 7.

The TDC circuit 12 of fig. 11 differs from the TDC circuit 12 of fig. 7 in that the capacitances of the capacitors 131-1 and 131-2 are 1: N, and current sources 181-1 and 181-2 are added instead of the current source 111. The other configuration is substantially similar to that of fig. 7, and thus description is omitted.

That is, the current sources 181-1 and 181-2 have a current mirror ratio of 1: N, and charge the capacitor 131-1 having the capacitance C1 and the capacitor 131-2 having the capacitance C2(═ N × C1) with current, respectively.

< operation of TDC Circuit >

Fig. 12 is a diagram illustrating an operation of the TDC circuit in fig. 11.

FIG. 12 shows, in order from the top, the signal waveform of the reference frequency signal Fref, the signal waveform of the DCO frequency signal Fdco, and the phase difference signal Φ_FThe voltage V generated in the capacitor 131-1(C1)_FAnd the voltage V generated in the capacitor 131-2(C2)_RAMPThe slope of (a).

Providing a phase difference signal Φ at time T21 from a rising edge of the reference frequency signal Fref_FWhen so, the switch 113-1 is turned on. Charging the capacitor 131-1 with current from the current source 181-1 and generating a voltage V in the capacitor 131-1_F. Next, the DCO frequency signal Fdco is supplied in one cycle from the time T22 of the rising edge of the DCO frequency signal Fdco, so that the switch 113-2 is turned on. Charging the capacitor 131-2 with current from the current source 181-2 and generating a voltage V in the capacitor 131-2_RAMP。

After the voltage is generated, the operation is substantially similar to the example of fig. 8, and thus a description thereof will be omitted.

As described above, the TDC circuit of FIG. 11 can simultaneously perform the voltage V_FAnd voltage V_RAMPWithout waiting for the voltage V_RAMPThe charging current of (a) for one cycle, and thus the AD conversion result can be obtained more quickly than the TDC circuit of fig. 7.

According to the present technology, the time for current charging from a current source can be shortened to improve the intermittent ratio, so that the power is reduced.

For example, the phase locked loop of the present technology is used in a high frequency wireless communication device.

<2 > second embodiment

< example of configuration of Wireless communication apparatus >

Fig. 13 is a block diagram showing a configuration example of a wireless communication device 200 including the ADPLL circuit 1. The wireless communication device 200 includes an ADPLL circuit 1, a modulation unit 201, a transmission mixer 202, a reference signal oscillator 203, a reception mixer 204, and a demodulation unit 205.

The ADPLL circuit 1 outputs a first local signal and a second local signal of a desired frequency to the transmission mixer 202 and the reception mixer 204, respectively, based on the reference signal output from the reference signal oscillator 203. Note that the reference signal oscillator 203 is configured using a crystal oscillator, for example.

The transmission mixer 202 is provided with a baseband transmission signal modulated by the modulation unit 400, and a first local signal output by the ADPLL circuit 1. The transmission mixer 202 up-converts the baseband transmission signal (BB transmission signal) into the high-frequency transmission signal (RF transmission signal) based on the supplied transmission signal and the first local signal. Note that the high-frequency transmission signal is transmitted via an antenna not shown in fig. 13.

Note that in the above description, an example used in a wireless communication device has been described, but the present technology is not limited to a wireless communication device and can be applied to an RF circuit or the like.

Further, the effects described in the present specification are merely examples and non-limiting, and other effects may be included.

The embodiments of the present technology are not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present technology.

Although the preferred embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, the present disclosure is not limited to these embodiments. It is apparent that those skilled in the art to which the present disclosure pertains can make various changes or modifications within the scope of the technical idea described in the claims. Of course, these changes or modifications are considered to fall within the technical scope of the present disclosure.

Note that the present technology may also take the following configuration.

(1)

A phase-locked loop circuit comprising:

a SAR-ADC including two capacitors and outputting a comparison result between voltages generated from the two capacitors;

a current source for charging the two capacitors with a current;

a first switch that is arranged between one of the two capacitors and the current source, and that is provided with a phase difference between a first clock of a reference frequency and a second clock having a frequency higher than the first clock; and

and a second switch arranged between the other of the two capacitors and the current source and provided with a second clock.

(2)

The phase-locked loop circuit according to the above (1), wherein,

based on the operation of the first switch, the current source charges one capacitor with a current for a time corresponding to the phase difference; and based on operation of the second switch, the current source charges the other capacitor with current for a time corresponding to the second clock.

(3)

The phase-locked loop circuit according to the above (2), wherein,

the time corresponding to the second clock is a time of one clock cycle or more.

(4)

The phase-locked loop circuit according to any one of the above (1) to (3), wherein,

one capacitor generates a voltage corresponding to the phase difference, and the other capacitor generates a voltage corresponding to the second clock.

(5)

The phase-locked loop circuit according to the above (4), wherein,

the capacitance ratio between one capacitor and the other is 1: 1.

(6)

The phase-locked loop circuit according to the above (4), wherein,

the current sources include a first current source that charges one capacitor with current, and a second current source that charges the other capacitor with current.

(7)

The phase-locked loop circuit according to the above (6), wherein,

the other capacitor has a capacitance N times that of the one capacitor, and

the second current source charges the other capacitor with a current N times that of the first current source.

List of reference marks

1 ADPLL circuit

11 counter circuit

12 TDC circuit

13 digital arithmetic circuit

14 VCO

111 current source

112 PD

113-1 and 113-2 switches

114 SAR_ADC

121 comparator

122 SAR _ logic circuit

131-1 and 131-2 capacitors

132-1 and 132-2 inverters

161-1 and 161-2 current sources

181-1 and 181-2 current sources

200 wireless communication device

201 modulation unit

202 transmission mixer

203 reference signal oscillator

204 receiving mixer

205 demodulation unit.