US20020024101A1 - CMOS bus driver circuit - Google Patents
CMOS bus driver circuit Download PDFInfo
- Publication number
- US20020024101A1 US20020024101A1 US09/886,826 US88682601A US2002024101A1 US 20020024101 A1 US20020024101 A1 US 20020024101A1 US 88682601 A US88682601 A US 88682601A US 2002024101 A1 US2002024101 A1 US 2002024101A1
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- circuit
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- mos transistor
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K19/00—Logic circuits, i.e. having at least two inputs acting on one output; Inverting circuits
- H03K19/003—Modifications for increasing the reliability for protection
- H03K19/00315—Modifications for increasing the reliability for protection in field-effect transistor circuits
Definitions
- the invention generally relates to bus driver circuits and more specifically to a CMOS bus driver circuit.
- driver circuit It is usual in integrated circuits to interconnect circuit units or also integrated circuits as a whole via a bus, a driver circuit being used as each stage coupling the circuit units and the bus.
- these driver circuits are configured as CMOS driver circuits in which both the input stage and the output stage consist of two complementary MOS transistors connected in series. This means that in the output stage the source-drain path of a PMOS transistor and the source-drain path of an NMOS transistor are connected in series between a supply voltage terminal and a ground terminal, the connection of the two source-drain paths forming the circuit output.
- driver circuits Since a variety of driver circuits are connected to the bus it may result in actual practice that a voltage occurs at the circuit output of a bus driver which is higher than the supply voltage of such a bus driver, this being especially the case when circuit units of several integrated circuit modules or integrated circuits each designed for a differing supply voltage are connected to a bus. Thus, it may happen that a driver applies to the bus a signal whose voltage value is higher than the supply voltage of another driver likewise connected to the bus.
- the PMOS transistor of the output stage is as a rule an enhancement-type transistor in which the gate voltage always needs to be the highest voltage existing in the circuit so that this transistor can be switched OFF. Should it happen, however, that the drain of this transistor receive from the bus a voltage which is higher than the supply voltage of the driver, then voltage is available to permit switching the PMOS transistor OFF by being applied to the gate. Indeed, the ON condition of the PMOS transistor materializing in this case could even result in it being ruined.
- the invention is thus based on the objective of providing a CMOS bus driver circuit of the aforementioned kind which at modest circuit expense is protected should a voltage be applied to the circuit output which is higher than the available supply voltage.
- a circuit output and the gate of a MOS transistor of the output stage the gate-source path of a further MOS transistor of the same channel type is connected whose gate is connected to the supply voltage terminal, that in the connection of the source-drain paths of the MOS transistors of the input stage a diode is inserted so that the flow of a current in the direction of the MOS transistor connected to the supply voltage terminal of the input stage is blocked, its cathode being connected to the gate of the one MOS transistor of the output stage, and that a blocking circuit component is provided which sets the output stage into a high impedance state when the driver circuit is not supplied with an enable signal for bus driving.
- FIG. 1 there is illustrated a bus driver circuit 10 containing an input stage comprising a PMOS transistor P 1 and an NMOS transistor N 1 .
- the gates of these two transistors are connected to each other and form a circuit input 12 of the bus driver circuit 10 .
- the source-drain paths of the two transistors are inserted in series between a supply voltage terminal 14 and a ground terminal 16 with a diode D in-between.
- the diode D is inserted between the two source-drain paths so that a flow of current in the direction of the PMOS transistor P 1 is prevented.
- the bus driver circuit 10 contains furthermore an output stage including a PMOS transistor P 2 and an NMOS transistor N 2 whose source-drain paths are connected in series between the supply voltage terminal 14 and ground terminal 16 .
- the point connecting the two source-drain paths forms the circuit output 18 of the bus driver circuit 10 .
- the gate of the PMOS transistor P 2 is connected to the point connecting the drain of the NMOS transistor N 1 and the cathode of the diode.
- the LO signal at the circuit output 18 results in PMOS transistor P 3 , whose gate is connected to the supply voltage, being switched OFF while the PMOS transistor P 4 is switched ON. It is due to PMOS transistor P 4 being switched ON that the diode D is short-circuited, i.e. taken out of circuit.
- the circuit input 12 also needs to receive such a HI signal.
- the transistors P 1 , P 2 , P 4 , N 1 and N 2 in the driver circuit change state, whereas the transistors P 5 , N 3 forming with the NOR circuit a blocking circuit component do not change state since the HI signal is still applied to the enable input EN, PMOS transistor P 3 likewise remaining OFF since its gate is applied to the highest voltage appearing in the circuit, namely the supply voltage.
- the diode D would negatively influence the bus driver circuit under normal circumstances, i.e. when no voltage appears at the circuit output 18 higher in value than the supply voltage.
- the forward voltage of the diode equal to or higher than the threshold voltage of PMOS transistor P 2 would prevent this PMOS transistor being switched OFF totally when a LO signal is required at the circuit output 18 .
- the threshold voltages of the field-effect transistors are assuming ever smaller values while the forward voltage of the diodes remains constant, resulting in this becoming a serious problem. Since, however, in the cited case the diode is bypassed by PMOS transistor P 4 so that its forward voltage can have no effect, PMOS transistor P 2 can be reliably switched OFF quickly.
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Computing Systems (AREA)
- General Engineering & Computer Science (AREA)
- Mathematical Physics (AREA)
- Logic Circuits (AREA)
- Electronic Switches (AREA)
Abstract
Description
- The invention generally relates to bus driver circuits and more specifically to a CMOS bus driver circuit.
- It is usual in integrated circuits to interconnect circuit units or also integrated circuits as a whole via a bus, a driver circuit being used as each stage coupling the circuit units and the bus. In modern integrated circuits these driver circuits are configured as CMOS driver circuits in which both the input stage and the output stage consist of two complementary MOS transistors connected in series. This means that in the output stage the source-drain path of a PMOS transistor and the source-drain path of an NMOS transistor are connected in series between a supply voltage terminal and a ground terminal, the connection of the two source-drain paths forming the circuit output. Since a variety of driver circuits are connected to the bus it may result in actual practice that a voltage occurs at the circuit output of a bus driver which is higher than the supply voltage of such a bus driver, this being especially the case when circuit units of several integrated circuit modules or integrated circuits each designed for a differing supply voltage are connected to a bus. Thus, it may happen that a driver applies to the bus a signal whose voltage value is higher than the supply voltage of another driver likewise connected to the bus.
- In integrated circuits the PMOS transistor of the output stage is as a rule an enhancement-type transistor in which the gate voltage always needs to be the highest voltage existing in the circuit so that this transistor can be switched OFF. Should it happen, however, that the drain of this transistor receive from the bus a voltage which is higher than the supply voltage of the driver, then voltage is available to permit switching the PMOS transistor OFF by being applied to the gate. Indeed, the ON condition of the PMOS transistor materializing in this case could even result in it being ruined.
- The invention is thus based on the objective of providing a CMOS bus driver circuit of the aforementioned kind which at modest circuit expense is protected should a voltage be applied to the circuit output which is higher than the available supply voltage.
- In an embodiment of the invention, a circuit output and the gate of a MOS transistor of the output stage the gate-source path of a further MOS transistor of the same channel type is connected whose gate is connected to the supply voltage terminal, that in the connection of the source-drain paths of the MOS transistors of the input stage a diode is inserted so that the flow of a current in the direction of the MOS transistor connected to the supply voltage terminal of the input stage is blocked, its cathode being connected to the gate of the one MOS transistor of the output stage, and that a blocking circuit component is provided which sets the output stage into a high impedance state when the driver circuit is not supplied with an enable signal for bus driving.
- FIG. 1: the sole FIGURE is a circuit diagram of the CMOS bus driver circuit in accordance with the invention.
- Referring now to this FIGURE there is illustrated a
bus driver circuit 10 containing an input stage comprising a PMOS transistor P1 and an NMOS transistor N1. The gates of these two transistors are connected to each other and form acircuit input 12 of thebus driver circuit 10. The source-drain paths of the two transistors are inserted in series between asupply voltage terminal 14 and aground terminal 16 with a diode D in-between. In this arrangement the diode D is inserted between the two source-drain paths so that a flow of current in the direction of the PMOS transistor P1 is prevented. - The
bus driver circuit 10 contains furthermore an output stage including a PMOS transistor P2 and an NMOS transistor N2 whose source-drain paths are connected in series between thesupply voltage terminal 14 andground terminal 16. The point connecting the two source-drain paths forms thecircuit output 18 of thebus driver circuit 10. The gate of the PMOS transistor P2 is connected to the point connecting the drain of the NMOS transistor N1 and the cathode of the diode. - Connected between the gate of the PMOS transistor P2 and the
circuit output 18 is the source-drain path of a further PMOS transistor P3 whose gate is connected to thesupply voltage terminal 14. Connected in parallel to the diode D is the source drain path of a further PMOS transistor P4, the gate of which is connected to thecircuit output 18. - Connected in parallel to the source-drain path of the PMOS transistor P1 is the source-drain path of a further PMOS transistor P5 whose gate is connected to the gate of an NMOS transistor N3, the source-drain path of which is connected between the source of the NMOS transistor N1 and ground. The connected gates of the PMOS transistor P5 and NMOS transistor N3 are connected via a negator N to an input of a NOR circuit X, the other input of which is connected to the
circuit input 12. The output stage of the NOR circuit X is connected to the gate of the NMOS transistor N2. In addition, the connected gates of the PMOS transistor P5 and NMOS transistor N3 are connected to an enable input EN. - The way in which the
bus driver circuit 10 works as shown in the drawing will firstly be described for the case in which a HI signal is applied to the enable input EN and with no voltage appearing at the bus connected to thecircuit output 18 which is higher than the supply voltage of the bus driver circuit applied to thesupply voltage terminal 14. Due to the HI signal at the enable input EN PMOS transistor P5 is switched OFF and NMOS transistor N3 is switched ON. Via the negator N a LO signal is applied to the one input of the NOR circuit. Assuming now a LO signal is required to be applied to the output stage of the circuit and thus to thecircuit output 18, then since the bus driver circuit has no inverting effect this is achieved by a LO signal likewise being applied to thecircuit input 12, resulting in PMOS transistor P1 being switched ON while NMOS transistor N1 is switched OFF. A high voltage thus appears at the gate of the PMOS transistor P2 which switches this transistor OFF. Via the NOR circuit X a high voltage signal appears at the gate of the NMOS transistor N2 which switches this transistor ON, resulting in, as desired, the LO signal appearing at thecircuit output 18 which is thus applied to the bus. The LO signal at thecircuit output 18 results in PMOS transistor P3, whose gate is connected to the supply voltage, being switched OFF while the PMOS transistor P4 is switched ON. It is due to PMOS transistor P4 being switched ON that the diode D is short-circuited, i.e. taken out of circuit. - Should the
circuit output 18 be required to produce a HI signal to be applied to the bus, then thecircuit input 12 also needs to receive such a HI signal. The transistors P1, P2, P4, N1 and N2 in the driver circuit change state, whereas the transistors P5, N3 forming with the NOR circuit a blocking circuit component do not change state since the HI signal is still applied to the enable input EN, PMOS transistor P3 likewise remaining OFF since its gate is applied to the highest voltage appearing in the circuit, namely the supply voltage. - Considering now the situation in which the driver circuit is deactivated by a LO signal applied to the enable input EN and in which a voltage is applied to the
circuit output 18 via the bus from another driver circuit which is higher than the supply voltage at the supply voltage terminal, then a LO signal at the enable input EN results in NMOS transistors N2 and N3 being switched OFF. As mentioned above, PMOS transistor P2 must always be switched opposite in state to that of the NMOS transistor N2 when the HI signal or the LO signal appears at thecircuit output 18, i.e. also when the voltage coming from the bus is higher than the supply voltage. The PMOS transistor P2 can thus only be reliably switched OFF when its gate receives the highest voltage available, i.e. normally the voltage at thesupply voltage terminal 14. If the voltage at thecircuit output 18 then assumes a higher value than the supply voltage it is normally no longer possible to switch PMOS transistor P2 OFF by applying its gate to the supply voltage. However, in the bus driver circuit as shown in the drawing PMOS transistor P3 ensures that in this case the higher voltage atcircuit output 18 is applied to the gate of PMOS transistor P2, resulting in this being reliably switched OFF. PMOS transistor P3 changes to the ON condition due to the higher voltage at thecircuit output 18 so that this output voltage appears via the source-drain path at the gate of the PMOS transistor P2. - Since, as already mentioned, NMOS transistors N2 and N3 are already OFF due to the LO signal at the enable input EN there is no flow of current from the
circuit output 18 via the PMOS transistor P3 and the NMOS transistor N1, neither toground terminal 16 nor to thesupply voltage terminal 14 since this is prevented, on the one hand, by the NMOS transistor N3 being OFF and, on the other, by the diode D. Thecircuit output 18 thus has a high impedance relative to the bus so that no current can flow from the bus into the driver circuit. Since in this arrangement the PMOS transistor P3 is ON, PMOS transistor P2 is reliably switched OFF in the output circuit stage so that it cannot be ruined by a current flowing from thecircuit output 18 to thesupply voltage terminal 14. - Without PMOS transistor P4 the diode D would negatively influence the bus driver circuit under normal circumstances, i.e. when no voltage appears at the
circuit output 18 higher in value than the supply voltage. The forward voltage of the diode equal to or higher than the threshold voltage of PMOS transistor P2 would prevent this PMOS transistor being switched OFF totally when a LO signal is required at thecircuit output 18. However, it is particularly in latest technology in the fabrication of integrated circuits that the threshold voltages of the field-effect transistors are assuming ever smaller values while the forward voltage of the diodes remains constant, resulting in this becoming a serious problem. Since, however, in the cited case the diode is bypassed by PMOS transistor P4 so that its forward voltage can have no effect, PMOS transistor P2 can be reliably switched OFF quickly. - In the bus driver circuit as described, it is reliably prevented under all circumstances that a current flows from the
supply voltage terminal 14 via the PMOS transistor P2 and NMOS transistor N2 to ground, this applying also to the critical case when the voltage at thecircuit output 18 is higher than the supply voltage. Short-circuiting the diode D with the aid of PMOS transistor P4 ensures in this case that the transition into the OFF condition takes place very quickly. For the switching actions the full supply voltage range can be exploited which is particularly of advantage when the supply voltage range assumes small values.
Claims (6)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10031837.1 | 2000-06-30 | ||
DE10031837A DE10031837C1 (en) | 2000-06-30 | 2000-06-30 | Complementary MOSFET bus driver circuit has input and output stages each provided with 2 complementary MOSFET's connected in series with diode between MOSFET's of input stage bridged by MOSFET |
DE10031837 | 2000-06-30 |
Publications (2)
Publication Number | Publication Date |
---|---|
US20020024101A1 true US20020024101A1 (en) | 2002-02-28 |
US6411125B1 US6411125B1 (en) | 2002-06-25 |
Family
ID=7647311
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/886,826 Expired - Lifetime US6411125B1 (en) | 2000-06-30 | 2001-06-21 | CMOS bus driver circuit |
Country Status (3)
Country | Link |
---|---|
US (1) | US6411125B1 (en) |
EP (1) | EP1168624B1 (en) |
DE (2) | DE10031837C1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090237126A1 (en) * | 2008-03-24 | 2009-09-24 | Elite Semiconductor Memory Technology Inc. | Gate driver for switching power mosfet |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE20120516U1 (en) * | 2001-12-19 | 2003-04-30 | Johnson Controls Gmbh | Ventilation system for an upholstered part |
US7332935B2 (en) * | 2006-06-21 | 2008-02-19 | Standard Microsystems Corporation | Driver with variable output voltage and current |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5338978A (en) * | 1993-02-10 | 1994-08-16 | National Semiconductor Corporation | Full swing power down buffer circuit with multiple power supply isolation |
US5600267A (en) * | 1994-06-24 | 1997-02-04 | Cypress Semiconductor Corporation | Apparatus for a programmable CML to CMOS translator for power/speed adjustment |
US5966026A (en) * | 1995-02-14 | 1999-10-12 | Advanced Micro Devices, Inc. | Output buffer with improved tolerance to overvoltage |
US5576635A (en) * | 1995-02-14 | 1996-11-19 | Advanced Micro Devices, Inc. | Output buffer with improved tolerance to overvoltage |
DE69521598T2 (en) * | 1995-03-31 | 2002-07-11 | Cons Ric Microelettronica | CMOS output buffer with three states |
DE19602456C1 (en) * | 1996-01-24 | 1997-04-10 | Texas Instruments Deutschland | BiCMOS-CMOS circuit with incorporated protection |
JP3340906B2 (en) * | 1996-03-13 | 2002-11-05 | 株式会社 沖マイクロデザイン | Output circuit |
US5892377A (en) * | 1996-03-25 | 1999-04-06 | Intel Corporation | Method and apparatus for reducing leakage currents in an I/O buffer |
US5952848A (en) * | 1997-03-14 | 1999-09-14 | Lucent Technologies Inc. | High-voltage tolerant input buffer in low-voltage technology |
US5926056A (en) * | 1998-01-12 | 1999-07-20 | Lucent Technologies Inc. | Voltage tolerant output buffer |
-
2000
- 2000-06-30 DE DE10031837A patent/DE10031837C1/en not_active Expired - Fee Related
-
2001
- 2001-06-21 US US09/886,826 patent/US6411125B1/en not_active Expired - Lifetime
- 2001-06-28 EP EP01114844A patent/EP1168624B1/en not_active Expired - Lifetime
- 2001-06-28 DE DE60126191T patent/DE60126191T2/en not_active Expired - Lifetime
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090237126A1 (en) * | 2008-03-24 | 2009-09-24 | Elite Semiconductor Memory Technology Inc. | Gate driver for switching power mosfet |
Also Published As
Publication number | Publication date |
---|---|
EP1168624A2 (en) | 2002-01-02 |
EP1168624A3 (en) | 2003-09-03 |
DE60126191T2 (en) | 2007-11-15 |
EP1168624B1 (en) | 2007-01-24 |
DE60126191D1 (en) | 2007-03-15 |
US6411125B1 (en) | 2002-06-25 |
DE10031837C1 (en) | 2001-06-13 |
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