LD5523K

05/16/2018

14

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD5523K-DS-00 May 2018

If VFB is greater than the FB OVP trip level, the internal

counter starts counting 8 cycles, and then LD5523K goes

to auto-recovery protection mode till the FB OVP status is

defused.

Over Temperature Protection on CS Pin (CS

OTP) - Auto Recovery

LD5523K is implemented over temperature protection on

CS pin which senses voltage to determine NTC status

during gate off region. As VCS is greater than 0.5V and

continues for 5.4ms, CS_OTP is triggered, than LD5523K

is in auto recovery mode till the temperature drops to

setting work condition.

Oscillator and Switching Frequency

The LD5523K is implemented with Frequency Swapping

function which helps the power supply designers to both

optimize EMI performance and lower system cost.

Secondary Diode Short Protection (SDSP) -

Auto Recovery

The method that the LD5523K judges the logic of SDSP is

described briefly as follows. When VCS is higher than

1.3V, it will reduce the frequency first, even the Ton <

LEB+TPD. When the count is up to 4 times, its gate will be

turned-off, shown as Fig. 20.

Fig. 20

Green Mode Operation

By using the green-mode control, the switching frequency

can be reduced under the light load condition. This feature

helps to improve the efficiency in light load conditions.

The green-mode control is Leadtrend Technology

’s own

property.

Fault Protection

There are several critical protections integrated in the

LD5523K to prevent from damage to the power supply.

Those damages usually come from open or short

conditions on the pins of LD5523K.

In case under such conditions listed below, the gate

output will turn off immediately to protect the power circuit.

1.

CS pin floating

2.

COMP pin floating

Comp

CS

1.3V

4 cycle