CS8129 datasheet(5/8 Pages) CHERRY

5 / 8 page

The CS8129

function has hysteresis on both the

reset and delay comparators, a latching Delay capacitor

discharge circuit, and operates down to 1V.

The

circuit output is an open collector type with

ON and OFF parameters as specified. The

output

NPN transistor is controlled by the two circuits described

(see Block Diagram).

This circuit monitors output voltage, and when output

voltage is below the specified minimum causes the

output transistor to be in the ON (saturation)

state. When the output voltage is above the specified level,

this circuit permits the

output transistor to go into

the OFF state if allowed by the

Delay circuit.

This circuit provides a programmable (by external capaci-

tor) delay on the

output lead. The Delay lead pro-

vides source current to the external delay capacitor only

when the "Low Voltage Inhibit" circuit indicates that out-

put voltage is above VRT(ON). Otherwise, the Delay lead

sinks current to ground (used to discharge the delay

capacitor). The discharge current is latched ON when the

output voltage is below VRT(OFF). The Delay capacitor is

fully discharged anytime the output voltage falls out of

regulation, even for a short period of time. This feature

ensures a controlled

pulse is generated following

detection of an error condition. The circuit allows

the

output transistor to go to the OFF (open) state

only when the voltage on the Delay lead is higher than

VDC(HI).

The Delay time for the

function is calculated from

the formula:

Delay time =

Delay time = CDelay(µF) x 3.2 x 105

If CDelay=0.1µF, Delay time (ms)=32ms ± 50%: i.e. 16ms to

48ms. The tolerance of the capacitor must be taken into

account to calculate the total variation in the delay time.

CDelay x VDelay Threshold

ICharge

RESET

Reset Delay Circuit

RESET

Low Voltage Inhibit Circuit

RESET

(1)

(2)

(3)

(2)

Delay

VOUT

VRT(ON)

VRT(OFF)

VRH

VDC(HI)

VDC(LO)

VDH

tDelay

VDIS

VRL

RESET

(1) = No Delay Capacitor

(2) = With Delay Capacitor

(3) = Max:

Voltage (1.0V)

RESET

Circuit Waveform

RESET

Circuit Functional Description

RESET

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