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Large Scale Integrated TTL Circuit Technology Utilizing Low Voltage Positive Supplies

IP.com Disclosure Number: IPCOM000085687D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 4 page(s) / 93K

Publishing Venue

IBM

Related People

Sechler, RF: AUTHOR

Abstract

A large-scale integration (LSI) circuit technology is provided, with positive supplies and standard TTL external signals, which allows utilization of low voltage nonsaturating TTL (transistor, transistor logic) circuits internal to an LSI chip.

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Large Scale Integrated TTL Circuit Technology Utilizing Low Voltage Positive Supplies

A large-scale integration (LSI) circuit technology is provided, with positive supplies and standard TTL external signals, which allows utilization of low voltage nonsaturating TTL (transistor, transistor logic) circuits internal to an LSI chip.

It has been determined that a low voltage nonsaturating TTL circuit performs well at low-power dissipation in an LSI implementation. The two features of the circuit, such as that shown in Fig. 1, which render it useful only in internal use on an LSI chip are its low I/O current gain and low down-level noise tolerance, when driven by like circuits.

Chip-to-chip communication compensates for these two features by utilizing an emitter-follower for chip exit, enhancing current gain and providing increased downlevel noise tolerance through the voltage translation of the emitter-follower. Such an implementation is useful only where the signal, power supply, and driver needs to be compatible with a current switch emitter-follower external circuit type. For many utilizations, where compatibility with industrial TTL circuitry is required, this implementation is not satisfactory.

For a positive supply implementation, the use of a high power chip exit circuit, of the type shown in Fig. 1, provides the required drive capability, but does nothing to increase the noise tolerance of the receiving circuit, since the same downlevel signal is provided. There is in fact no way to improve the noise tolerance of the receiver circuit via the driver circuit with a positive power supply set. What is required is a higher threshold receiver circuit such as that shown in Fig. 2. The use of a circuit like this along with a higher power driver, provides the combination of increased gain and noise tolerance with chip exit and entry on an LSI chip.

The chip entry circuit of Fig. 2 must allow a mix of on-chip and off-chip inputs to be a useful general purpose circuit. The external and internal levels are not generally the same in an LSI implementation using a low voltage internal circuit. Compatibility demands the mixing of input types as shown in Fig. 3, where the ...