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THV3012_Rev.1.00_E

THine Electronics, Inc.

Copyright©2009 THine Electronics, Inc.

Functional Description

THV3012 has soft start circuit allows a gradual rising of output voltage to prevent overshooting of output volt-

age and high inrush current during start up. When UVLO is released and CTL pin is turned High level, an inter-

nal 2uA constant current source starts to charge an external capacitor connected to SS pin.

Css connected between SS pin and GND is determined by soft start time. Soft start time is the period of charg-

ing SS pin to the reference voltage 0.85V with 2uA constant current source, and calculated as following :

When Tss=4.25msec, Css=0.01uF.

THV3012 has the built-in Undervoltage Lockout circuit to prevent the device from misoperation at low input

voltages. UVLO stops switching operation and soft start operation, until VIN and VCC voltage rise up to

4.2V(typ). Having the hysteresis circuit, UVLO stops switching operation and start to discharge SS pins, when

VIN voltage falls down under 4.15V(typ), or VCC voltage falls down under 4.05V(typ).

THV3012 has the built-in Over Current Protection circuit to limit over current caused by abnormal load cur-

rent, etc. When a voltage difference between CSN pin and CSP pin exceeds 60mV(typ), OCP detects over cur-

rent.

OCP circuit monitors the bottom current of inductor to detect over current. When the voltage between CSN pin

and CSP pin drops below 60mV(typ), High side FET generates on-pulse. Therefore the average value of ripple

current

is added to the output current as following :

rip

I

OU T

I

=

S

R

V

m

60

+

RIP

I

2

1

(A)

SCP circuit is activated, when the output voltage drop continues. After soft start operation is finished and feed-

back voltage drops less than 0.6V(typ), SCP detects a short circuit. If such condition continues for more than

4.1msec(typ), the device stops switching operation and go into latch state. The latch state will be released by

restarting to apply voltage on CTL pin, VIN pin or VCC pin.

THV3012 has the built-in Thermal Shutdown circuit to prevent damages caused by excessive heat. When the

junction temperature

reaches 125 ℃ (typ), TSD circuit stops switching operation. When

falls down

(20

typical hysteresis), the output voltage will recover.

°C

j

T

j

T

°C

out

I

L

I

s

R

mV

60

Tss =

Α

u

2

V

85

0.

SS

C

= 0.425×

6

×