CS8126 datasheet(5/9 Pages) CHERRY

5 / 9 page

The CS8126

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).

Low Voltage Inhibit Circuit

This circuit monitors output voltage, and when the output

voltage falls below VRT(OFF), causes the

output tran-

sistor to be in the ON (saturation) state. When the output

voltage rises above VRT(ON), this circuit permits the

output transistor to go into the OFF state if allowed by

the

Delay circuit.

RESET 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 falls 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(H1).

The Delay time for the

function is calculated from

the formula:

Delay time =

Delay time = CDelay ´ 3.2 ´ 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 ´ VDelay Threshold

ICharge

RESET

RESET Circuit Waveform

VRH

VOUT

VRT(ON)

VRT(OFF)

VRL

Delay

VDC(HI)

VDC(LO)

VDH

tDelay

VDIS

(3)

(1)

(2)

RESET

(1) = No Delay Capacitor

(2) = With Delay Capacitor

(3) = Max: RESET Voltage (1.0V)

Circuit Description

CS8126 Datasheet(PDF) 5 Page - Cherry Semiconductor Corporation

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