LMC6953 Datasheet, PDF (1/12 Pages) National Semiconductor (TI) – PCI Local Bus Power Supervisor

April 1998
LMC6953
PCI Local Bus Power Supervisor
General Description
The LMC6953 is a voltage supervisory chip designed to
meet PCI (Peripheral Component Interconnect) Specifica-
tions Revision 2.1. It monitors 5V and 3.3V power supplies.
In cases of power-up, power-down, brown-out, power failure
and manual reset interrupt, the LMC6953 provides an active
low reset. RESET holds low for 100 ms after both 5V and
3.3V powers recover, or after manual reset signal returns to
high state. The external capacitor on pin 8 adjusts the reset
delay.
This part is ideal on PCI motherboards or add-in cards to en-
sure the integrity of the entire system when there is a fault
condition. The active low reset sets the microprocessor or lo-
cal device in a known state.
The LMC6953 has a built-in bandgap reference that accu-
rately determines all the threshold voltages. The internal re-
set delay circuitry eliminates additional discrete components.
Features
n Compliant to PCI specifications revision 2.1.
n Under and over voltage detectors for 5V and 3.3V
n Power failure detection (5V falling under 3.3V by
300 mV max)
n Manual reset input pin
n Guaranteed RESET assertion at V_DD = 1.5V
n Integrated reset delay circuitry
n Open drain output
n Adjustable reset delay
n Response time for over and under voltage detection:
490 ns Max
n Power failure response time: 90 ns Max
n Requires minimal external components
Applications
n Desktop PCs
n PCI-Based Systems
n Network servers
Typical Application Circuits
On Mother Board
On Add-in Cards
DS012846-23
DS012846-24
© 1998 National Semiconductor Corporation DS012846
www.national.com