阅读说明：本技术 逆变器电路装置 (Inverter circuit device ) 是由 胡安·米格尔·加维尔莱罗 于 2019-03-27 设计创作，主要内容包括：一种连接IO链路主设备与从设备的逆变器电路装置,包括AB类晶体管电路(Q_(nc2)、Q_(pc2)),该AB类晶体管电路的电流由电流镜(Q_(po1)、Q_(no1)、Q_(po2)、Q_(no2))复制到从设备的端子(OUT1)。偏置电路(R_(b1)、Q_(b1)、...、Q_(nc1)、Q_(pc1))为AB类晶体管(Q_(nc2)、Q_(pc2))提供偏置电压。比较器(C)在主设备端子与从设备端子(C/Q、OUT1)之间形成反馈。该电路提供双向逆变,以使从设备与IO链路兼容。(Main equipment and slave equipment for connecting IO linkInverter circuit arrangement comprising a class AB transistor circuit (Q) nc2 、Q pc2 ) The current of the AB class transistor circuit is controlled by a current mirror (Q) po1 、Q no1 、Q po2 、Q no2 ) To the terminal of the slave device (OUT 1). Bias circuit (R) b1 、Q b1 、...、Q nc1 、Q pc1 ) Is a class AB transistor (Q) nc2 、Q pc2 ) A bias voltage is provided. The comparator (C) forms a feedback between the master and slave terminals (C/Q, OUT 1). The circuit provides bidirectional inversion to make the slave compatible with the IO link.)

1. An inverter circuit device comprising:

a first terminal (OUT1), a second terminal (C/Q), for a first supply potential (V)_{Power supply}) And for the second supply potential (V)_Ground) A terminal of (1);

pull-up resistor (R)₃) Connected to the first terminal (OUT1) and to the first supply potential (V)_{Power supply}) A terminal of (1);

class AB transistor circuit (Q)_nc2、Q_pc2) Connected to the second terminal (C/Q);

first current mirror (Q)_po1、Q_po2) Having a connection to a potential (V) for said first supply_{Power supply}) And to the class AB transistor circuit (Q)_nc2、Q_pc2) And having an output path connected to said first terminal (OUT 1);

second current mirror (Q)_no1、Q_no2) Having a potential (V) connected to said second supply potential (V)_Ground) And to the class AB transistor circuit (Q)_nc2、Q_pc2) And has an output path connected to said first terminal (OUT 1);

bias circuit (R)_b1、Q_b1、…、Q_nc1、Q_pc1) Comprising a bias current source (R)_b1、Q_b1) For being in relation to said first potential (V)_{Power supply}) First bias voltage of (V_bn) And for being in relation to the second supply potential (V)_Ground) Second bias voltage (V)_bp) Wherein for the first and second bias voltages (V)_bn、V_bp) Is connected to the class AB transistor circuit (Q)_nc2、Q_pc2) (ii) a And

a comparator (C) connected to the first terminal (OUT1), the output of the comparator passing through a third current mirror (Q)_d2、Q_d1) Is connected to the second terminal (C/Q).

2. The inverter circuit device according to claim 1,

wherein the AB class transistor circuit includes a PNP transistor (Q)_pc2) And NPN transistor (Q)_nc2) Emitters of the PNP transistor and the NPN transistor are connected to the second terminal (C/Q).

3. The inverter circuit device according to claim 1 or 2,

wherein the comparator (C) comprises a first input (-) connected to a threshold voltage and a second input (+) connected to the first terminal (OUT1), wherein the output of the comparator is connected to a resistor (R)₁) Wherein the third current mirror (Q)_d2、Q_d1) Comprising an input path connected to said resistor and an output path connected to said second terminal (C/Q).

4. The inverter circuit device according to claim 3,

wherein the first input (-) of the comparator (C) is connected to a voltage divider (R)₂、R₂) And a second input (+) of said comparator is a non-inverting input connected to said first terminal (OUT 1).

5. The inverter circuit device according to any one of claims 1 to 4,

current mirror (Q)_pc1、Q_pc2) Configured to receive the bias current (I)_b) And having a transistor (Q) comprising said class AB transistor circuit_pc2) The output path of (a);

another current mirror (Q)_nc1、Q_nc2) Configured to receive the bias current (I)_b) And having a further transistor (Q) comprising said class AB transistor circuit_nc2) The output path of (1).

6. The inverter circuit device according to claim 5,

wherein the current mirror (Q) of the bias circuit_pc1、Q_pc2) Comprising an input path including a connection to a first supply potential (V)_{Power supply}) Diode (D) of the terminal₂) And a transistor (Q) configured to be connected to the class AB transistor circuit_pc2) Of the control terminal of (2)_pc1)，

Wherein the other current mirror (Q) of the bias circuit_nc1、Q_nc2) Comprises an input path including a connection to the second supply potential (V)_Ground) Diode (D) of the terminal₁) And a further transistor (Q) configured to be connected to the class AB transistor circuit_nc2) Of the control terminal of (2)_nc1)。

7. The inverter circuit device according to any one of claims 1 to 6,

further comprising a main circuit (130) having an output terminal (131) connected to the second terminal (C/Q), the main circuit comprising an output terminal (131) connected to the main circuit and a voltage for the second supply potential (V)_Ground) Of a first switchable current source (134, IQL)_M) An output terminal (131) connected to the main circuit and for the second supply potential (V)_Ground) Of the terminal of (133, ILL)_M) And an output terminal (131) connected to the main circuit and for the first supply potential (V)_{Power supply}) Third of the terminalsSwitching current source (132, IQH)_M)。

8. The inverter circuit device according to claim 7,

further comprising a slave circuit (110) having an output terminal (111) connected to said first terminal (OUT1), said slave circuit comprising a connection to said second supply potential (V)_Ground) And a switchable current source (112, IQL) connected to an output terminal (111) of the slave circuit_D)。

9. The inverter circuit device according to claim 8,

wherein the terminal for the first supply potential is for a positive potential (V)_{Power supply}) And the terminal for the second power supply potential is for ground potential (V)_Ground) Wherein is connected to the terminal for the positive potential (V)_{Power supply}) Comprises a PNP transistor and is connected to the ground potential (V)_Ground) The current mirror of the terminal of (1) comprises an NPN transistor.

10. The inverter circuit arrangement according to claim 8 or 9, wherein the slave circuit (110) comprises an open collector drive transistor, the collector of which is connected to the first terminal (OUT1) and the emitter of which is connected to the second supply potential (V |)_Ground) The terminal of (1).

11. Inverter circuit arrangement according to one of claims 8 to 10, wherein the master circuit (130) comprises an output stage complying with part 9 of european specification EN 61131 and the slave circuit comprises an output stage not complying with part 9 of european specification EN 61131.

12. Inverter circuit arrangement according to one of claims 8 to 11, wherein the circuit is configured such that the current supplied by the output of the comparator (C) is higher than the current supplied by the output of the comparator (C)Second current source (133, ILL) of main circuit_M) A current supplied and less than a first switchable current source (134, IQL) of the main circuit_M) And a second current source (133, ILL) of the main circuit_M) The sum of the supplied currents.

Technical Field

The present disclosure relates to a circuit arrangement providing a bidirectional inverter function. In particular, the present disclosure relates to a circuit arrangement providing a bidirectional inversion between a first terminal and a second terminal for connecting a master circuit according to european specification EN 61131 part 9 with a slave circuit not complying with this specification.

Background

European specification EN 61131 part 9, often also referred to as IO link, relates to the need to connect a slave to a master by a cable having at least three wires in an industrial environment. A slave device is typically a sensor or actuator that interfaces with a master device through peer-to-peer communication of an IO link, where the master device may be plugged into a fieldbus of a higher level control system. The IO link master comprises a switchable current source in a push-pull configuration and the IO link slave comprises a switchable high-side current source such as an open collector PNP transistor. The current signal is transmitted through a signal line, where the master or slave supplies a high side current through an open collector PNP transistor, or the master sinks a pull-down current through a pull-down resistor.

The use of low-side current switches, such as open collector NPN transistors, instead of high-side current switches, makes these sensor devices incompatible with the IO link and incapable of instant communication with the IO link master device.

It is desirable to provide a circuit that establishes an interface between a master device compatible with an IO link and a slave device incompatible with the IO link. In particular, there is a need for a circuit that interfaces between an IO link master device having an output stage that uses a push-pull circuit and a slave device having a low side open collector switching transistor.

It is an object of the present disclosure to provide a device that performs an interface between a master device compatible with an IO link and a slave device incompatible with the IO link.

It is another object of the present disclosure to provide an interface circuit that enables connecting a sensor device having a low side switch to an IO link master device having a high side switch.

Disclosure of Invention

One or more of the above objects are achieved by an inverter circuit device comprising: a first terminal, a second terminal, a terminal for a first power supply potential, and a terminal for a second power supply potential; a pull-up resistor connected to the first terminal and to a terminal for a first power supply potential; a class AB transistor circuit connected to the second terminal; a first current mirror having an input path connected to a terminal for a first power supply potential and connected to one end of the class AB transistor circuit, and an output path connected to the first terminal; a second current mirror having an input path connected to a terminal for a second power supply potential and connected to the other end of the class AB transistor circuit, and an output path connected to the first terminal; a bias circuit including a bias current source, a terminal for a first bias potential with respect to a first potential, and a terminal for a second bias potential with respect to a second power supply potential, wherein the terminals for the first bias voltage and the second bias voltage are connected to the class AB transistor circuit; and a comparator connected to the first terminal, an output of the comparator being connected to the second terminal through a third current mirror.

The inverter circuit device includes a first terminal OUT1 connected to an output terminal of the slave device. The slave device may comprise a low side switchable current source connected between the output terminal and a ground terminal. The low side current source may be an open collector NPN transistor. The inverter circuit arrangement includes a second terminal C/Q connected to an output terminal of the master device. The master device includes at least a high side switchable current source connected to a positive power potential terminal and a low side switchable current source connected to a ground terminal in a push-pull configuration. The inverter circuit arrangement fulfills the function of an interface circuit which connects signals with logical behavior between an IO link master and a slave which is not compatible with the IO link. The circuit arrangement performs the function of a bidirectional inverter.

In more detail, the interface circuit includes a pull-up resistor at the first terminal OUT 1. The C/Q terminal is connected to a class AB transistor circuit, wherein the emitters of both complementary bipolar NPN and PNP transistors are connected to the C/Q terminal. The current through the class AB transistor is fed back to the OUT1 terminal through a corresponding current mirror circuit.

The bias circuits supply respective bias voltages to the base terminals of the class AB transistors. The bias voltage enables only one of the class AB transistors to be turned on. For example, the bias voltage is one or two diode potentials above or below the supply voltage. For high-side class AB transistors, the bias voltage is one or two diode potentials above ground. For low side class AB transistors, the bias voltage is one or two diode potentials below the positive supply potential. The bias voltage is generated by a current source that produces a defined current that is mirrored by one or more current mirror circuits into a path connected to ground or supply potential and including at least one diode. The diode is connected to the base terminal of the class AB transistor. The class AB behavior of class AB transistors minimizes power consumption and the temperature effects resulting from the power consumption of the device.

A comparator is provided at the OUT1 terminal. The comparator output supplies a current through a resistor, which is mirrored to terminal C/Q. The non-inverting input of the comparator is connected to the terminal OUT1 and the inverting input of the comparator is connected to a voltage divider that can generate a midpoint voltage, for example, half the supply voltage. If the signal at terminal OUT1 is high, the output of the comparator is driven high, for example to the supply potential, so that no output current is generated in the resistor. If the signal at terminal OUT1 is low, the output of the comparator is driven low, e.g., to ground potential, causing a current to be generated in the resistor that is mirrored to terminal C/Q.

In more detail, the bias circuit comprises a bias current source connected to the positive supply potential, which may be a resistor having a known defined value, such that it produces a defined current through the diode. The diode is the input path of the current mirror. Another current mirror associated with one of the class AB transistors receives the bias current through an additional current mirror circuit, wherein the class AB transistor forms an output path of the associated current mirror. The current mirror associated with the high side class AB transistor is connected to ground potential and the current mirror associated with the low side class AB transistor is connected to supply potential. The emitters of the input paths of the current mirrors may be directly connected to ground potential and to supply potential, respectively, or bias voltages of one or more diode voltages above ground potential and below supply potential, respectively, may be generated by additional diode devices.

The current to be supplied to terminal C/Q, produced by the comparator output, must be within a range defined by the current of the master. This current must be higher than the pull-down current through the low-side resistor of the master device. In addition, the current must also be lower than the sum of the currents through the low-side switch and through the low-side pull-down resistor of the master device. The appropriate amount of current can be determined by a resistor connected to the output of the comparator.

When an inverter circuit arrangement according to the present disclosure is connected between an output terminal of an IO-link compatible master device and an output terminal of an IO-link incompatible slave device having a low-side open collector NPN transistor as a low-side switch instead of an IO-link compatible high-side switch, the incompatible slave device is enabled to cooperate with the IO-link master device. The slave device may be a sensor or an actuator. In particular, the slave device may be an inductive proximity sensor, the output of which may comprise a low-side NPN transistor with a pull-up resistor. The sensor may be a sensor with a high voltage default output. The device is capable of communicating via an IO link protocol using NPN transistors at the device output. The inverter circuit arrangement may be comprised in the slave device or may be a separate printed circuit board arrangement connected to the output of the slave device.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments and, together with the description, serve to explain the principles and operations of the various embodiments. Like elements in different figures of the drawings are denoted by like reference numerals.

Drawings

In the drawings:

FIG. 1 illustrates a top-level block diagram of a circuit according to the principles of the present disclosure; and

fig. 2 shows a detailed schematic diagram of an inverter circuit connected between a slave and a master of the apparatus of fig. 1.

Detailed Description

The present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will fully convey the scope of the disclosure to those skilled in the art. The drawings are not necessarily to scale, but are configured to clearly illustrate the disclosure.

Top level block diagram

The top-level block diagram of fig. 1 shows a master device 130 including an IO link compatible output stage. The output terminal 131 is provided with a switchable high-side current source 132 which supplies a current IQH in response to a switching signal (on/off)_M. The low-side current source 133 sinks a current ILL from the terminal 131_MTo ground potential. The low side current source may be a resistorA device. The further switchable low-side current source 134 sinks a current IQL in response to the switching signal (on/off)_MTo ground potential. The switchable high-side current source and the switchable low-side current source operate in a push-pull configuration and may be implemented with pnp and npn transistors, respectively.

The slave device 110 may be a sensor or an actuator. The slave device 110 may be, inter alia, a proximity sensor. The proximity sensor comprises a switchable low-side current source 112 connected between the output 111 and ground potential. Switchable current source 112 sinks current IQL in response to a switching signal (on/off)_D. The low-side current source may be an open collector NPN transistor, the collector of which is connected to the output terminal 111 and the emitter of which is connected to ground potential. The base of the NPN transistor is controlled to be on or off, indicating the function of the slave device. Alternatively, the low-side current source may be an open-drain NMOS transistor.

An interface circuit 120 is provided between the terminals 111 and 131, which interface circuit is matched to the physical layer between the output terminals of the master device 130 and the slave device 110, i.e. between the terminals 131 and 111. The interface circuit 120 is a bi-directional inverter that makes the IO link master device compatible with slave devices having a low side switch, such as an open collector NPN transistor, as an output stage. The circuit 120 inverts the master input/output current at terminal C/Q to terminal OUT1 for slave input/output and at the same time utilizes a class a/B transistor current comparator to limit the C/Q voltage range. These comparators turn off the appropriate current from either the high side or the low side depending on the polarity of the C/Q current. As will be explained in more detail below, by proper selection of the current magnitude, the circuit is also able to override the main pull-down current at terminal C/Q when terminal OUT1 is driven low. In the idle state, the interface circuit provides a pull-up resistor at the terminal OUT1 such that the terminal OUT1 remains at a logic "1" and the master pull-down current maintains the terminal C/Q at a "0".

Detailed schematic diagram of inverter circuit

The detailed structure of the circuit 120 is depicted in fig. 2. The schematic of circuit 120 includes a positive power supply connected to terminal OUT1Potential V_{Power supply}Pull-up resistor R of terminal₃. In the example, the positive supply potential V_{Power supply}May be 24V, and resistor R₃May be in the range of 200 omega. The terminal C/Q of the circuit 120 is connected to a class AB transistor Q_nc2And Q_pc2. NPN transistor Q_nc2Is connected to the PNP transistor Q_pc2And is connected to terminal C/Q. Transistor Q_nc2And Q_pc2Is connected to a corresponding current mirror that copies the current through these transistors to terminal OUT 1. Specifically, the PNP transistor Q_po1Connected to an NPN transistor Q_nc2Collector and supply potential V_{Power supply}In the meantime. Transistor Q_po1Is configured as a diode and is connected to a transistor Q including a PNP transistor_po2The PNP transistor Q_po2Is connected to terminal OUT 1. NPN transistor Q_no1Connected to a PNP transistor Q_pc2And is connected to ground potential V_Ground. Transistor Q_no1Is configured as a diode and copies current to an output path of a current mirror comprising a ground potential V connected at a terminal OUT1_GroundNPN transistor Q therebetween_no2。

The bias circuit shown at the right hand side of the schematic comprises a current source to supply a current I_bResistor R_b1Is connected to a supply potential V_{Power supply}. Current I_bFlow through diode connected transistor Q_b1The transistor copies the current to be connected at a power supply potential V_{Power supply}And ground potential V_GroundIn the current mirror arrangement in between. The current mirror device includes a high side current mirror and a low side current mirror. The high side current mirror includes a diode connected PNP transistor Q_b4And output PNP transistor Q_b5The two transistors being connected to a supply potential V_{Power supply}. The low side current mirror comprises an NPN transistor Q_b2And NPN transistor Q_b3The bases of which are connected together and to a current source transistor Q_b1All transistors being connected to ground potential V_Ground. Thus, current flowI_bAlso flows through the transistor Q_b5And Q_b3。

Is further connected to a transistor Q_b5Is another current mirror comprising an NPN transistor Q configured as a diode_nc1The emitter of the NPN transistor passes through a diode D₁Connected to ground potential V_Ground. The output side of the current mirror comprises a high-side class AB transistor Q_nc2. Transistor Q_nc1、Q_nc2Common base carrying bias potential V_bn. At the low-side part, a transistor Q_b3Connected to another current mirror comprising a PNP transistor Q configured as a diode_pc1The emitter of the PNP transistor passes through a diode D₂Connected to a supply potential V_{Power supply}. The output side of the current mirror comprises a low-side class AB transistor Q_pc2. Transistor Q_pc1、Q_pc2Common base carrying bias potential V_bp. Bias potential V_bn、V_bpRespectively with respect to ground potential V_GroundAnd a power supply potential V_{Power supply}Fixed at the two diode voltages. The diode D can be omitted₁、D₂So that the bias voltage V is_bn、V_bpFixed above or below potential V_Ground、V_{Power supply}At the voltage of one diode.

The feedback path between terminals OUT1 and C/Q includes comparator C. The non-inverting input "+" of comparator C is connected to terminal OUT 1. The inverting input "-" of the comparator C is connected to a voltage divider connected at the supply voltage V_{Power supply}To ground potential V_GroundIn the meantime. The voltage divider is symmetrical in that it comprises two identical resistors R₂The midpoint of the resistor is connected to the inverting input of comparator C. The voltage divider supplies a threshold voltage to the comparator to compare the voltage at terminal OUT1 with the threshold voltage. The output of the comparator C is connected to a resistor R₁The resistor is a PNP transistor Q including a diode connection_d2And output PNP transistor Q_d1Is part of the current mirror circuit of (a). Transistor Q_d2、Q_d1Is connected to a supply potential V_{Power supply}. Crystal grainTransistor Q_d1Is connected to the terminal C/Q and supplies a current I_d。

Can be in the transistor Q_b4、Q_b2Between the collectors of and in the transistor Q_no1、Q_pc2Collector and Q_po1、Q_nc2Between the collectors of which a resistor (not shown in the drawings) is arranged. These resistors lower the respective collector voltages.

Operation of inverter circuit

The operation of the circuit depicted in fig. 2 is as follows. Transistor Q_b1And a resistor R_b1Defines a bias current I_bThe bias current is used to bias the current comparator at terminal C/Q. By a transistor Q_b1、Q_b2And Q_b3Formed current mirror and transistor Q_b4And Q_b5The current mirror formed replicates pass transistor Q_pc1And Q_nc1The current of (2).

Through diode D₁And a transistor Q_nc1Current of (I)_bLimiting potential V_bnAnd through a diode D₂And a transistor Q_pc1Current of (I)_bLimiting potential V_bp. Only when the voltage at terminal C/Q is below V_bn-Vbe_nc2(Vbe_nc2: transistor Q_nc2Base emitter voltage) current can flow through the transistor Q_nc2. Only when the voltage at terminal C/Q is higher than V_bp+Veb_pc2(Vbe_pc2: transistor Q_pc2Base emitter voltage) current can flow through the transistor Q_pc2. Therefore, no current can flow through the two transistors Q simultaneously_nc2And Q_pc2Thereby achieving class AB behavior. Quiescent current from the power supply through these transistors to ground is avoided.

Comparator C compares the voltage at terminal OUT1 with one-half V of the supply voltage_{Power supply}/2. If the voltage at terminal OUT1 is above the threshold, the output voltage of comparator C is set to V_C＝V_{Power supply}So that no current flows through the resistor R₁. If the voltage at terminal OUT1 is lower thanThe threshold value is set to V, the output voltage of the comparator C is set to V_C＝V_GroundSo as to pass through the transistor Q_d1And Q_d2The current mirror of (a) injects the current flowing through the resistor R1 at terminal C/Q. When the potential at the terminal OUT1 is low, through the resistor R₁Current of

I_d＝(V_{Power supply}–Vbe_d2-V_C)/R₁

When the potential at the terminal OUT1 is high, the current I_d0. The function of the comparator C can be summarized as follows:

OUT1＝H，V_C＝V_{power supply}，I_d＝0

OUT1＝L，V_C＝V_Ground，I_d＝(V_{Power supply}–Vbe_d2-V_C)/R₁

IO Link Master utilization Current ILL_MTo pull down the potential at terminal C/Q. In the idle state, neither the master nor the slave generates other currents. Thus, terminal C/Q is pulled low, and current ILL_MFlow-through transistor Q_nc2. This current is passed by transistor Q at terminal OUT1_po1And Q_po2Such that the potential at terminal OUT1 is pulled up. To avoid terminal OUT1 floating and going low, a higher than current ILL is injected at terminal C/Q_MCurrent of (I)_dSo as to pass through the resistor R₃Also pulls up terminal OUT 1.

When the master wants to send a bit "1" after the idle state (start bit) or after the previous bit "0", it utilizes the higher than current ILL_MCurrent IQH of_MTo pull up the terminal C/Q. Differential current IQH_M-ILL_MFlow-through transistor Q_pc2And at terminal OUT1 by transistor Q_no1And Q_no2Is replicated by the current mirror. Differential current IQH_M-ILL_MMust be higher than the pass resistor R₃Current V of_{Power supply}/R₃Enabling the master to place the terminal OUT1 low. When terminal OUT1 is low, current I_dAlso injected at terminal C/Q, which forces terminal C/Q to pull up.

When the master wants to send a bit "0" after the previous bit "1", the current IQL will be utilized_MAnd a pull-down terminal C/Q. Current ILL_MWill also pull down the terminal C/Q and the current I_dThe terminal C/Q will be pulled up. Current IQL_M+ILL_M-I_d(greater than 0) flow through transistor Q_nc2And at terminal OUT1 by transistor Q_po1And Q_po2By means of a resistor R₃Pulling up terminal OUT 1. When terminal OUT1 is high, current I_dBecomes zero and flows through the transistor Q_nc2Is IQL_M+ILL_M。

When the master stops transmitting after the stop bit (bit "1"), terminal C/Q is pulled down by current ILLM. The current I is activated because the terminal C/Q was previously pulled up_d. When current I_dHigher than current ILL_MThe terminal C/Q is not pulled down until the resistor R₃Terminal OUT1 is brought high.

When the slave device wants to send a bit "1" at the terminal C/Q after the previous idle state or after the previous bit "0", an open-drain NPN transistor should be connected at its output stage, pulling down the terminal OUT 1. When current I_dHigher than current ILL_MWhen a current I appears_dAnd the terminal C/Q is pulled up.

When the slave is to send a "0" at terminal C/Q from the previous bit "1" or return to an idle state, the open-drain NPN transistor is turned off and resistor R₃Pulling up terminal OUT 1. When OUT1 is high, current I_dIs zero, and the current ILL_MThe terminal C/Q can be pulled down.

Thus, for the current I_dThe constraint being that it should be higher than the current ILL_MAnd is less than the current IQL_M+ILL_M。

The inverter circuit 120 inverts a current and a voltage between the IO link master device and other devices that cannot generate a high quiescent current to pull up a voltage of the signal line. By using the inverter circuit 120, such slave devices can communicate using the IO link protocol even at maximum speed.

It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosure as defined in the appended claims. Since modifications, combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the disclosure may occur to persons skilled in the art, the disclosure should be construed to include everything within the scope of the appended claims.