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Controlled Voltage Swing Terminator for Open-Collector Driver

IP.com Disclosure Number: IPCOM000039439D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Cavaliere, JR: AUTHOR [+2]

Abstract

A controlled voltage swing terminator circuit for open collector drivers, offering such advantages as reduced signal swing, terminator power, drive power and signal current, is described in this article. A conventional open-collector driver and terminating circuit employed with a multi-driver or bidirectional net is shown in Fig. 1. Excessive signal swing and sinking current encountered with this arrangement may be reduced by the use of a split terminator, but this saving is offset by the increased terminator power plus the added DC and transient currents to ground if the split terminator goes to ground. (Image Omitted) In Fig. 2, a controlled voltage swing terminator circuit is employed to reduce signal swing, to lower sinking current, and to reduce both terminator and driver power.

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Controlled Voltage Swing Terminator for Open-Collector Driver

A controlled voltage swing terminator circuit for open collector drivers, offering such advantages as reduced signal swing, terminator power, drive power and signal current, is described in this article. A conventional open-collector driver and terminating circuit employed with a multi-driver or bidirectional net is shown in Fig. 1. Excessive signal swing and sinking current encountered with this arrangement may be reduced by the use of a split terminator, but this saving is offset by the increased terminator power plus the added DC and transient currents to ground if the split terminator goes to ground.

(Image Omitted)

In Fig. 2, a controlled voltage swing terminator circuit is employed to reduce signal swing, to lower sinking current, and to reduce both terminator and driver power. Circuit 1 (with the terminating resistor) in Fig. 2 functions to sense the line voltage and reacts in such a way as to achieve these goals. Terminal 1 provides the line voltage signal to the circuit, and terminal 2 is the output response of the circuit. An implementation of this circuit is shown in Fig. 3. The line up-level is determined by the values of R3, R4, R1 and the Vbe of the transistor T2. Down- level sinking current is determined by the value of R1, the Vbe of transistor T1, and the value of R2. The line current is limited by the value of R2, while the down-level is determined by the drivers. An open-collector dr...