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Latched Off-Chip Receivers With Current Steering

IP.com Disclosure Number: IPCOM000119861D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 70K

Publishing Venue

IBM

Related People

Montegari, F: AUTHOR

Abstract

The latched receiver circuit with PNP current steering (Fig. 1) receives an off-chip address signal through an NPN ECL circuit, latches it into another NPN ECL circuit, and supplies dual-phase outputs to its loads. Current steering that switches from receive to latch mode is done in a PNP ECL circuit that passes its current into the NPN ECL circuits.

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Latched Off-Chip Receivers With Current Steering

      The latched receiver circuit with PNP current steering
(Fig. 1) receives an off-chip address signal through an NPN ECL
circuit, latches it into another NPN ECL circuit, and supplies
dual-phase outputs to its loads.  Current steering that switches from
receive to latch mode is done in a PNP ECL circuit that passes its
current into the NPN ECL circuits.

      NPN bipolar transistors T1, T2 are emitter followers that
provide a high impedance to the input signal and shift it down one
VBE .  The lower levels at the emitters of T1, T2 allow ECL circuit
transistors T3, T4 to supply larger transitions at their collectors
without producing saturation within those devices.  The larger
transitions are useful for driving FET devices.

      Receiver transistors T3, T4, are collector dotted with latch
transistors T8, T9, which are driven by emitter followers T6, T7,
whose bases are cross-coupled to the collector nodes of T8, T9 to
form the latch.

      Current sources T5, T10 are driven by mirror devices T11 and
T12, and current is steered either into T11 to receive the incoming
signal or into T12 to latch the data, by the PNP ECL circuit T15,
T16.  A clock input at the base of T15 switches from receive to latch
mode.  Current is supplied to T15, T16 by PNP current source T13 and
mirror device T14.

      The latched off-chip receiver with ECL current steering (Fig.
2) functions in a manner similar to the...