US 5,852,372 AGranted

Apparatus and method for signal handling on GTL-type buses

AssigneeIntergraph Corporation

InventorsEduard F. Boeckmann, Vern Brethour, Vahid Samiee

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Abstract

Transceivers for bus communications using GTL-type transmission-line bus structures provide improved clamping of an initially ON output pulse of a communication bus driver and adds an active pull-up function inside the integrated circuit that does not change the external circuit nor require additional functional external circuit corrections. Receivers may contain an active pull-up for added signal quality improvement Improved clamping and active pull-up allow reduced width of the channel of the N-channel CMOS output transistor. A drive/receive clamp may be added to a sequential pull-up circuit and an active pull-up circuit for better performance at higher frequencies. A related method may comprise first switching OFF an active pull down circuit and switching ON an active pull-up circuit, where the active pull-up circuit clamps the driver output voltage from falling below a first voltage. Then switching OFF a first clamping circuit, where the first clamping circuit clamps the driver output voltage from exceeding a second voltage when the first damping circuit is ON, and where the second voltage is greater than the first voltage. And then switching OFF a second clamping circuit, where the second clamping circuit clamps the driver output voltage from exceeding a third voltage when the second clamping circuit is ON, and where the third voltage is greater than the second voltage.

Claims27

Dependent claims

A driver for providing bus signals at a driver output in response to an input signal, the driver having a driver input responsive to the input signal, a supply voltage terminal, and a ground terminal, the driver comprising:

(a) a first switching element having a switching state responsive to the input signal to provide a low impedance between the driver output and the ground terminal when the first switching element is ON and to provide a high impedance between the driver output and the ground terminal when the first switching element is OFF;
(b) a second switching element having a switching state responsive to the input signal to provide a high impedance between the driver output and the supply voltage terminal when the second switching element is OFF,
wherein the first and second switching elements are switched in a complementary fashion so that when the first switching element is switched from ON to OFF the second switching element is switched from OFF to ON and when the first switching element is switched from OFF to ON the second switching element is switched from ON to OFF;
(c) a first clamping device to provide a non-linear resistance diode-action between the driver output and the ground terminal when the second switching element is ON;
(d) a first delay element having an input responsive to the input signal, and an output with a voltage;
(e) a third switching element having a switching state responsive to the output voltage of the first delay element, so as to provide a high impedance between the driver output and the ground terminal when the third switching element is OFF;
(f) a second clamping device to provide a non-linear resistance diode-action between the driver output and the ground terminal when the third switching element is ON;
(g) a second delay element having an input responsive to the output voltage of the first delay element, and an output with a voltage;
(h) a fourth switching element having a switching state responsive to the output voltage of the second delay element to provide a high impedance between the driver output and the ground terminal when the fourth switching element is OFF;
and
(i) a third clamping device to provide a non-linear resistance diode-action between the driver output and the ground terminal when the fourth switching element is ON.

8 more elements

A communications system, comprising:

(a) a communication bus;
(b) a driver for providing bus signals on the communication bus in response to an input signal, the driver having:
i. a first and a second complementary switch responsive to the input signal,
(1) the first complementary switch having low impedance between the driver output and the ground terminal when ON, and having high impedance when OFF, and
(2) the second complementary switch having a high impedance between the driver output and the supply voltage terminal when the switch is OFF,
so that when the first switch is switched from ON to OFF the second switch is switched from OFF to ON and when the first switch is switched from OFF to ON the second switch is switched from ON to OFF;
ii. a first clamping device to provide a non-linear resistance diode-action between the driver output and the supply voltage terminal when the second switch is ON;
iii. a first delay element having an input responsive to the input signal, and an output with a voltage;
iv. a third switch responsive to the output voltage of the first delay element, to provide a high impedance between the driver output and the ground terminal when OFF;
v. a second clamping device to provide a non-linear resistance diode-action between the driver output and the ground terminal when the third switching element is ON;
vi. a second delay element having an input responsive to the output voltage of the first delay element, and an output with a voltage;
vii. a fourth switch responsive to the output voltage of the second delay element, to provide a high impedance between the driver output and the ground terminal when OFF;
and
viii. a third clamping device to provide a non-linear resistance diode-action between the driver output and the ground terminal when the fourth switching element is ON.

11 more elements

(a) a first switch responsive to the input signal, having low impedance between the driver output and the ground terminal when the first switch is ON, and high impedance when the first switch is OFF;
(b) a second switch responsive to the input signal, having high impedance between the driver output and the supply voltage terminal when the second switch is OFF;
(c) a first load between the driver output and the ground terminal;
(d) a first delay element having an input responsive to the input signal, and an output with a voltage;
(e) a third switch responsive to the output voltage of the first delay element, having high impedance between the driver output and the ground terminal when the third switching element is OFF;
and
(f) a second load between the driver output and the ground terminal when the third switching element is ON;
wherein the first and second switches are switched in a complementary fashion so that when the first switch is switched from ON to OFF the second switch is switched from OFF to ON.

5 more elements

Dependencies are inferred from the claim text.