LD7835

11

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD7835-DS-01 July 2015

Over Current Protection (OCP)

The LD7835 detects the MOSFET current from the CS

pin, which is for the pulse-by-pulse current limit and

output

current

feedback.

The

maximum

voltage

threshold of the CS pin is set at 1.2V. From above, the

MOSFET peak current can be obtained from below.

��������

=

����

����

Over Voltage Protection (VCC OVP)

The maximum rating of the VCC pin is limited below 30V.

To prevent VCC from damage due to fault condition, the

LD7835 is implemented with OVP function on VCC pin,

this value is about 28V. As soon as the VCC voltage is

over OVP threshold voltage, the output gate drive circuit

will be shutdown simultaneously thus to stop the

switching of the power MOSFET until the next UVLO

(ON) arrives. The VCC OVP function of the LD7835 is

an auto-recovery protection. The Fig. 18 shows its

operation. Upon removal of the OVP condition will

resume the VCC level and the output operation

VCC

UVLO(ON)

UVLO(OFF)

t

OVP Tripped

t

OUT

Switching

Switching

Non-Switching

OVP Level

Fig. 18

Output Drive Stage

An output stage of a CMOS buffer, with typical

250mA/-250mA driving capability, is incorporated to

drive the power MOSFET directly.

The output voltage

is clamped at 13V to protect the MOSFET gate even

when the VCC voltage rises over 13V.