Browse Prior Art Database

Power Supply Supervisor and Reset Generator

IP.com Disclosure Number: IPCOM000112753D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 63K

Publishing Venue

IBM

Related People

Baumgartner, SJ: AUTHOR [+4]

Abstract

A temperature-compensated power supervisor and reset generator circuit is disclosed. The power supervisor generates a Power-On-Reset (POR) control signal that drives low once the power supply voltage has reached a threshold (Vth) and remains low for a controlled period of time (Td).

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Power Supply Supervisor and Reset Generator

      A temperature-compensated power supervisor and reset generator
circuit is disclosed.  The power supervisor generates a
Power-On-Reset (POR) control signal that drives low once the power
supply voltage has reached a threshold (Vth) and remains low for a
controlled period of time (Td).

      The power supervisor generates a low POR signal once the power
supply voltage has reached a threshold (Vth).  In addition, the POR
signal must remain low for a controlled period of time (Td) so the
control logic has enough time to reset (Fig. 1).

      It also has hysteresis so that the POR signal doesn't bounce on
and off as the power supply voltage slowly rises.  The power supply
threshold has to be high enough to assure proper control logic
operation but below normal power supply variations and tolerances.
This typically leaves less than 500 mV margin of error in the
threshold level.

      The circuit shown in Fig. 2 provides the power supervisor
function.  The first function is to compare the power supply voltage
to a temperature-compensated reference so the threshold has minimal
temperature dependance.  This is done with the voltage divider, R1
and R2, and the bandgap circuit, Q1-Q4 and R7-R10.  The threshold
occurs when node 1 reaches the temperature-compensated bandgap
voltage (approx.  1.1V).  As the supply rises from 0V, the voltage at
node 5 is lower than node 6.  When node 1 equals 1.1V, node 5 equals...