Browse Prior Art Database

Matrix Current Steering Driver/Receiver Pair

IP.com Disclosure Number: IPCOM000060725D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Larsen, TA: AUTHOR

Abstract

The problem addressed concerns the high probability that all columns on a given switch matrix chip will switch at the same time. Assuming standard voltage drivers and receivers, there would be significant transient capacitance current, i.e., C(out) DV/Dt. (C(out) is the column capacitance associated with each switching column driver.) This transient current results in significant voltage shifts on voltage planes due to inductance of package connectors (i.e., L Di/Dt). As a result of such limitations, the number of drivers which may switch simultaneously is limited by the package, driver design and loading capacitance. Such limitations would cause the need for additional chips to create the matrix function just to limit the simultaneous switching problem.

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Matrix Current Steering Driver/Receiver Pair

The problem addressed concerns the high probability that all columns on a given switch matrix chip will switch at the same time. Assuming standard voltage drivers and receivers, there would be significant transient capacitance current,
i.e., C(out) DV/Dt. (C(out) is the column capacitance associated with each switching column driver.) This transient current results in significant voltage shifts on voltage planes due to inductance of package connectors (i.e., L Di/Dt). As a result of such limitations, the number of drivers which may switch simultaneously is limited by the package, driver design and loading capacitance. Such limitations would cause the need for additional chips to create the matrix function just to limit the simultaneous switching problem. A solution to the problem is the use of current-steering driver- receiver pairs, as shown in Figs. 1 and 2. The concept of this scheme is to virtually eliminate transient capacitance current by maintaining the driver output voltage level virtually constant and driving a small, control LED (light-emitting diode) current to the one receiver which has been activated. The driver is basically a current switch circuit as shown (T2, T3, T4 or T9, T10, T11). The overall function is as follows: A receiver T7 to be activated is selected (all other receivers on the column line are biased off). Voltage at node N6B is set to 2.4 V. T7 will be on, and node N6 will be at
1.8 V; however, no current will flow because drivers T4 and T9 are biased off (not selected as yet). All other receivers sharing the node N6 are biased off (at 1.6
V). Assumi...