LD7516C

08/31/2016

12

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD7516C-DS-01 August 2016

Out

Fig. 21

OVP (Over Voltage Protection) on Vcc

–

Auto Recovery

LD7516C is implemented with OVP function through Vcc.

As the Vcc voltage rises over the OVP threshold voltage,

the output drive circuit will be shut off simultaneously thus

to stop the switching of the power MOS until the next

UVLO(on) arrives. The Vcc OVP function of LD7516C is

an auto-recovery type protection. The Fig. 22 shows its

operation. That is, if the OVP condition is removed, it will

resume to normal output voltage and Vcc level in normal

condition.

VCC

UVLO(on)

UVLO(off)

t

OVP Tripped

t

OUT

Switching

Switching

Non-Switching

OVP Level

Fig. 22

FB Under Voltage Protection (FB UVP) &

FB Short Circuit Protection

– Auto Recovery

LD7516C is implemented with an UVP function over FB

pin. If the FB voltage falls below UVP level over the delay

time, the protection will be activated to stop the switching

of the power MOS until the next UVLO(on) arrives. The

FB UVP function in LD7516C is an auto-recovery type

protection. The Fig. 23 shows its operation. During the

soft start period, the FB UVP is disabled. To avoid output

over voltage in soft start period. The Fig. 24 shows the

operation. While FB is short to GND, FB pin keeps in zero

voltage level. If FB cannot detect any voltage signal over

0.15V in the beginning of soft start period, then the soft

start will turn to generate a driving signal every 4ms until

FB UVP delay to shut down IC and auto recovery.

FB

UVP Level

t

FB UVP

Tripped

t

OUT

Switching

Switching

Non-Switching

Vcc

t

FB UVP

Delay Time

UVLO(on)

UVLO(off)

Soft Start

+

FB UVP

Delay Time

Fig. 23

FB

FB Short

Level

t

FB Short

t

CS

Non-

Switching

Vcc

t

UVLO(on)

UVLO(off)

Soft Start

+

FB UVP

Delay Time

OUT

t

Fig. 24