LD7752GS datasheet(12/17 Pages) LEADTREND

12 / 17 page

LD7752

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD7752-DS-01 June 2013

Protection Resistor on the Hi-V Path

In some other Hi-V process and design, there may be a

parasitic SCR caused around HV pin, Vcc and GND. As

shown in Fig. 15, any small negative spike on the HV pin

may trigger this parasitic SCR and cause latch-up

between Vcc and GND. It will damage the chip because

of the equivalent short-circuit induced by the latch-up

behavior.

With

Leadtrend’s proprietary of Hi-V technology, the

LD7752 is free from parasitic SCR. Fig. 10 shows the

equivalent circuit for it. The LD7752 is stronger to

sustain negative voltage than the other similar products.

However, a 10K

 resistor is recommended to add on

the Hi-V path to play as a current limit resistor whenever

a negative voltage is applied.

VCC

GND

Other HV

process with

parasitic SCR

Negative-triggered Parasitic SCR.

Any small negative spike on HV pin

will cause latchup between Vcc and

GND.

Fig. 15

VCC

GND

LD7752 is free from

parasitic effect between

HV, Vcc and GND

The current limit resistor

here is to prevent damage

from Negative voltage

(recommended)

Fig. 16

Frequency Swapping

The LD7752 is built-in with programmable frequency

swapping

function.

enables

the

power

supply

designers to optimize EMI performance and system cost.

The Frequency Swapping was internally set at

4KHz

when incorporating with 65KHz switching frequency.

On-Chip OTP

– Auto Recovery

An internal OTP circuit is embedded to provide the

worst-case protection for this controller. If the chip

temperature rises higher than the trip OTP level, the

output will be disabled until the chip is cooled down

below the hysteresis window.

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