LD7890GS datasheet(10/16 Pages) LEADTREND

10 / 16 page

LD7890

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD7890-DS-01 November, 2013

Fig. 7 VIN=24V, VOVP=60V , 250mA/string “LED OPEN”

VSTATUS

COMP

VOUT

IOUT

Fig. 8 VIN=24V, VOVP=60V, FDIM=200Hz,Duty=5%,“LED Open”

VOUT

COMP

IOUT

VSTATUS

Fig. 9 VIN=24V, 250mA/string, RFB=820k, “LED Short”

VSTATUS

COMP

VOUT

IOUT

Fig. 10

VIN=24V,250mA/string,RFB=820k,“LED Short”

IOUT

COMP

VOUT

VSTATUS

Application Information

The LD7890 high-efficiency driver is ideal for LED

backlight

application.

incorporates

DC-DC

boost

controller of peak current-mode control and 4 channel

LED driver.

LD7890 features adaptive voltage control that adjusts the

converter output voltage according to the total forward

voltage of LED strings. It minimizes the voltage drop

across the constant current-sink drivers and enhances

power dissipation in the device. It also integrates with LED

short and open protection, cycle by cycle current limit, and

thermal shutdown.

Current-Mode DC-DC Controller and UVLO

The peak current-mode controller allows boost converter

to generate the required output voltage for LED strings.

The switching frequency is programmable in the range

between

100kHz

and

600kHz

through

resistor

connected between RT pin and ground.

As the external MOSFET is turned on, the inductor current

will ramp up linearly until it reaches the peak current level

set by CS pin. The peak inductor current is sensed by

measuring the voltage across the current-sense resistor

RCS, which is connected between the source of external

MOSFET and ground. LD7890 features leading edge

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