LD7592 datasheet(10/15 Pages) LEADTREND

10 / 15 page

LD7592

06/05/2017

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD7592-DS-00 June 2017

Where Ra and Rb are top and bottom feedback resistor

values (as shown in the Fig. 10).

Vref = 2.5V

COMP

2.675V/

2.55V

0.45V/

0.35V

UVP

OVP

Disable

INV

Fig. 10

OVP and Disable Function

To prevent the over voltage on the output capacitor from

the fault condition, LD7592 is implemented with an OVP

function on INV pin. Whenever the INV pin voltage is

higher than OVP, the output gate drive circuit will be

shutdown simultaneously to stop the switching of the

power MOSFET until the INV pin down to (OVP -

OVP_HYS).

The

OVP

function

LD7592

auto-recovery type protection. The Fig. 11 shows its

operation.

The disable comparator disables the operation of the

LD7592 when the voltage of the inverting input is lower

than 0.35V and there is 100mV hysteresis. An external

small signal MOSFET can be used to disable the IC. If the

IC is disabled, operating current decreases below 100

μA

to reduce power consumption.

The

LD7592

can

provide

additional

over

voltage

protection on OVP pin. If INV pin voltage divider gets

damaged, then OVP pin can supply additional over

voltage protection. If OVP pin protection is not required,

the OVP pin can connect with INV pin.

INV

OVP Tripped

OUT

2.675V

2.55V

OFF

Fig. 11

Brown in Protection

The LD7592 features Brown-in function on INV pin. The

built-in comparator detects the VINV and VOVP voltage

condition, as shown in Fig. 12. This is done as follows:

1. The INV and OVP voltage is higher than UVP

2. The COMP voltage rise up and higher than VZDC

UVP

VComp

OUT

OFF

VINV.VOVP

VZDC

Fig. 12

Ramp Generator Block

The output of the gm error amplifier and the output of the

ramp generator block are compared to determine the

MOSFET on time, as shown in Fig. 13. The slope of the

ramp is determined by an external resistor connected to

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