Browse Prior Art Database

Current Mode Line Driver Short Circuit Fault Detection And Power Reduction

IP.com Disclosure Number: IPCOM000120143D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Larson, TR: AUTHOR [+2]

Abstract

Disclosed is a circuit that significantly reduces the short circuit power dissipation of current mode line drivers. It allows smaller, faster, more reliable, low-current drivers to be densely packed into cost efficient ICs. Also provided is short circuit error detection and non-latching current foldback protection.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 92% of the total text.

Current Mode Line Driver Short Circuit Fault Detection And Power
Reduction

      Disclosed is a circuit that significantly reduces the
short circuit power dissipation of current mode line drivers.  It
allows smaller, faster, more reliable, low-current drivers to be
densely packed into cost efficient ICs.  Also provided is short
circuit error detection and non-latching current foldback protection.

      In the figure, devices 1, 2 and 3 with current reference 9
implement a current mode driver.  Output device 3 supplies current to
the load when reference 9 forces the proper gate-to-source voltage on
mirror device 2.  Switch device 1, when conducting, turns off the
driver by bypassing mirror device 2.

      During an output to ground short circuit condition, VOUT drops
below the threshold set by voltage reference 8. Comparator 6 responds
by raising its output.  If enabled by delay circuit 4, the error
output gate 5 signals a short circuit condition on VFAULT.  Delay
circuit 4 enables gate 5 only when the driver is active and after
VOUT has had time to rise.

      When VFAULT signals a short circuit condition, switch 12 opens
and reduces the current supplied to device 2 by reference 9.  This
decreases the gate-to-source voltage of output device 3, lowering the
output current to the load.

      Normal operation of the driver resumes after removal of the
short circuit.  VOUT rises in the absence of a short, causing
comparator 6 to lower its output....