Philips Semiconductors

Product data

SA56614-XX

CMOS system reset

2001 Jun 19

7

TECHNICAL DESCRIPTION

The SA56614-XX is a CMOS device designed to monitor the

system’s power source and provide a system reset function in the

event the supply voltage sags below an acceptable level for the

system to reliably operate. The SA56614 generates a compatible

reset signal for a wide variety of microprocessor and logic systems.

The device can operate at voltages up to 12 volts. The series

includes several versions providing precision threshold voltage reset

values of 2.0, 2.7, 2.8, 2.9, 3.0, 3.1, 4.2, 4.6, and 4.7 V. The reset

prevent erratic resets from being generated. The SA56614 operates

at very low supply currents, typically 0.25

µA, while offering a high

precision of threshold detection (

±2%).

The output of the SA56614 incorporates an active Totem-Pole

output topology comprised of complimentary P-Channel and

N-Channel FETs. A P-Channel FET is on the high supply side and

which output source current can be obtained. A complimentary

N-Channel FET is on the low or ground side, and actively pulls the

output LOW or to ground with the capability of sinking current into

the output. Both devices supply system reset signals. The user

should keep in mind, when connecting the SA56614 to a system, the

effect of supplying source current from the output of the SA56614 on

the system. This is of particular importance where the SA56614 is

operated from a different supply source than the rest of the system.

Figure 12 is a functional block diagram of the SA56614. The internal

temperature range. The reference voltage is connected to the

non-inverting input of the threshold comparator while the inverting

input monitors the supply voltage through a resistor divider network

drives the totem-pole output stage of the device.

When the supply voltage sags to the threshold detection voltage, the

resistor divider network supplies a voltage to the inverting input of

the output of the comparator to adopt a HIGH output state. This

causes the high side P-Channel FET of the Totem-Pole output stage

to turn OFF while simultaneously turning the low side N-Channel

FET from OFF to an active ON state, pulling the output to a LOW

voltage state. The device adheres to a true input/output logic

protocol. The output goes to a LOW voltage state when input is

by turning ON whenever the threshold comparator’s output goes to

pulled even lower. For the comparator to reverse its output polarity

additional pull-down voltage present on the comparator’s inverting

input. The differential voltage required to do this establishes the

hysteresis voltage of the sensed threshold voltage. Typically it is

or lower cause the output to be pulled to ground.

Hysteresis Voltage = Release Voltage – Detection Threshold Voltage

where:

less than 0.95 volts, the output is undefined and output reset low

combination achieves very efficient low power performance over the

full operating temperature.

SL01353

NE56614-XX

1

R

3

2

Figure 12. Functional diagram