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ZERO CURRENT DRAIN CURRENT REFERENCE STARTUP

IP.com Disclosure Number: IPCOM000006120D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Dec-05
Document File: 1 page(s) / 50K

Publishing Venue

Motorola

Related People

Kevin McLaughlin: AUTHOR

Abstract

The current reference circuits commonly used in paging have two stable operating states. One state is the desired state where the operating current is set by a delta Vbe and a resistor (Rl). The other state is undesired, and is the zero current state. In all previous designs, a large resistor (typically 700K) was used to insure the circuit is biased to the desired state. This resistor takes a lot of area on the integrated circuit chip and consumes power.

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MOTOROLA INC. Technical Developments Volume 12 April 1991

ZERO CURRENT DRAIN CURREtjT

REFERENCE STARTUP ~

by Kevin Mclaughlin

  The current reference circuits commonly used in paging have two stable operating states. One state is the desired state where the operating current is set by a delta Vbe and a resistor (Rl). The other state is undesired, and is the zero current state. In all previous designs, a large resistor (typically 700K) was used to insure the circuit is biased to the desired state. This resistor takes a lot of area on the integrated circuit chip and consumes power.

  The resistor can be eliminated by using an edge detection circuit to generate a start pulse to shift the operation of the circuit to the desired state. When a high signal is applied to the input HON to switch on the current reference, MOS transistor M5 turns on to apply power to the current reference formed by

bipolar transistors Q2, 93, Q4, Q5, and resistor Rl. However, the current reffrence circuit may still power up in the zero current state, which is undesirable. An edge detector formed byiresistor R2, capacitor C3, and the XOR gate coupled to the input HON and the current reference circuit'and will generate a pulse and turn on MOS transistor M4 for a brief time (time=R2*C3). This tiill turn on Q2 and Q3. This will put the circuit into the desired state. After the brief time period has elapsed (time constant=R2*C3), MOS transistor M4 wiil be turned off by the XOR. The edge detector...