Datasheet

cui.com
date 01/26/2016 │ page 7 of 8CUI Inc │ SERIES: V78-500-SMT │ DESCRIPTION: NON-ISOLATED SWITCHING REGULATOR
TheON/OFF pinprovides several features foradjusting andsequencingthe powersupply, auserhas theflexibility of using theON/OFFpin as:
1) Adigital on/off controlbypulling down theON/OFFpin with an open-drain transistor.
ON/OFF
2) Line UVLO. If desiredtoachieveaUVLO voltage, aresistordivider from VintoON/OFFtoGND canbeusedtodisable theconverter until
ahigherinput voltageisachieved. Forexample,itisnot useful foraconverterwith12V output to star tupwitha12Vinput ,as the
output cannot each regulation.Toenablethe converterwhenthe inputvoltage reaches14V,a51kΩ/5kΩ voltage dividerfromVin to GN
D
canbeconnected to theON/OFF pin. Both theprecision 1.25Vthreshold and150mV hysteresis aremultipliedbythe resistor rati
o,
providingaproportional 12%hysteresisfor anystartup threshold. So,the turn offthreshold wouldbebetween 12.3V to 15.7V.
7,9
5
Vin
GND
+Vout
100F
1
V78XX-500-SMT
C1
6
470pF
10
51KΩ
5KΩ
Load
3) Powersupply sequencing. By connecting asmall capacitor from ON/OFF to GND, the 2 Acurrent source and1.25V thresholdcan provid
e
astableand pr edictabledelay betweenstartup of multiple powersupplies. Forexample,astartupdelay of roughly64mSisprovidedusi
ng
100nF, androughly 136mSbyusing 200nF.
7,9
5
Vin
GND
+Vout
100F
1
C1
6
470pF
10
100nF
C5
Load
CH1: Von/off
CH2: Vo
Delaytime: 64mS
7,9
5
Vin
GND
+Vout
100F
1
C1
6
470pF
10
200nF
C5
Load
CH1: Von/off
CH2: Vo
Delaytim e: 136mS
V78XX-500-SMT
V78XX-500-SMT
SHUTDOWN CONTROL
For more information, please visit the product page.