LD7890GS datasheet(12/16 Pages) LEADTREND

12 / 16 page

LD7890

Leadtrend Technology Corporation

www.leadtrend.com.tw

LD7890-DS-01 November, 2013

0.2V

1.2V

100%

DIM

Voltage

PWM DUTY

MOSFET Over-Current Protection

The LD7890 provides cycle-by-cycle current limit to

protect the MOSFET. During the MOSFET turn-on,

LD7890 will reduce DRV duty cycle once it detects VCS

rises above 0.5V, approximately.

Output

over

Voltage

and

LED

Open

Protection

As OVP pin is approaching the threshold voltage 2.5V, the

device will start to detect the SENSE pins. If there is any

of these pins stays below 0.2V, it appears to have some

channel failure. The LED driver will turn off the failure

ones and pull low the STATUS pin.

Place the bypass capacitor between OVP and signal

ground as close as possible. It will suppress the noise and

protect OVP from abnormal condition.

Unused LED Channel

If there

’s any output channel is unused, connect the

particular SENSEN with 100K resistor to GND and short

GateN and FBN together with a 220k resistor to route

with SenseN pin.

Gate n

Sense n

FB n

220K

100K

LED String Short Protection

The function block below provides LED short-circuit

protection whenever short circuit of LED module occurs.

In condition of VD -ISPxRSP > VLEDSP, it will send a signal to

pull low STATUS and turn off the failed LED channel.

Vout

VLEDSP

LED Short

Protection

ISP

RSP

FBx

Thermal protection

Thermal protection limits total power dissipation in this

device. When the junction temperature reaches 150

C

approximately, the thermal sensor signals the shutdown

logic to turn off the device. The thermal sensor will not

resume until

the IC’s junction temperature cools down

approximately 30°C.

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