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AC Write Scheme for Bipolar Random Access Memories using Schottky Coupled Cells

IP.com Disclosure Number: IPCOM000051975D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Dorler, JA: AUTHOR [+4]

Abstract

The write circuitry (scheme) presently used with the complementary transistor switch cell (Fig. 1) is a direct coupled DC voltage type. The power expended with this scheme is about 0.5 watt, or 20% of the entire chip power.

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AC Write Scheme for Bipolar Random Access Memories using Schottky Coupled Cells

The write circuitry (scheme) presently used with the complementary transistor switch cell (Fig. 1) is a direct coupled DC voltage type. The power expended with this scheme is about 0.5 watt, or 20% of the entire chip power.

The write scheme described in this article is an AC coupled voltage type. Since most of the write power is transient, the average power required to write is dramatically reduced; however, write performance is maintained compared with the present scheme.

Fig. 2A is a schematic representation of the transient write scheme. Transistors 13, 14, 15, 16, 17 along with current source JW define the write circuitry. These circuits are replicated once per column. Junctions J9 and J10 provide the AC coupling from the write circuits to the bit lines. These devices are replicated once per bit line pair. Diodes D1 and D2 provide a reset path for the unused coupled energy and are also replicated once per column.

Operation: During a read operation, transistors 3, 4, 13, 14, 16 and 17 are off, transistor 15 and diodes D1 and D2 are on, and nodes voltage B3 and B4 are BS1-VBE. The bit line voltages are determined by the selected cell current flow through the bit line resistors R1L, R1R.

During a write cycle, first T15 is turned off and either transistor 16 or 17 is turned on, depending on the state of the data-in circuits. Current is drawn through bit select transistors 1 and 2 and write junctions J9 or J10. It should be noted that junctions J9 and J10 are base-collector ju...