Browse Prior Art Database

Current Driver with Output Enable

IP.com Disclosure Number: IPCOM000111429D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Emeigh, R: AUTHOR [+4]

Abstract

A method for enabling and disabling a current driver is disclosed. The manipulation of the output pins enables and disables the driver in this method.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 68% of the total text.

Current Driver with Output Enable

      A method for enabling and disabling a current driver is
disclosed.  The manipulation of the output pins enables and disables
the driver in this method.

      A current driver that is enabled or disabled by forcing the
outputs to a specific voltage or ground is shown in the Figure.

      In disable mode the outputs, nodes 10 and 11, are grounded.
This forces NET26, NET12 and NET4 low.  Transistors Q7, Q14, Q13, Q19
and D5 are turned off when NET4 is forced low.  The voltage at the
base of Q39 is always 2 diodes above ground, and when the outputs are
grounded, Q39 turns on and begins conducting the current required by
the current mirror formed by Q37 and Q32.  Q31 and Q3 are turned off
and NET17 is forced low as the current through Q39 develops a voltage
across R15.  Q47 and Q18 could saturate with their collectors
grounded.  Net13 and NET39 are kept close to ground by level shifting
the voltage at NET17 down 3 diodes through Q49, Q4 and Q6, D1 and D0.
R13 and R14 provides a path to ground for this network and ensures
that Q49, Q4, Q6, D1 and D0 remain on in disable mode.  When NET17 is
low, the circuit providing input to the driver could saturate
transistors Q0 and Q2, so diodes D11 and D12 were added to prevent
this.  The voltage at NET17 is critical, and to provide some
temperature and power supply variation compensation a current
reference was added.  This reference is formed by R22, D13, D15, D16,
D17, D14, D...