MAP3204 Просмотр технического описания (PDF) - MagnaChip Semiconductor

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MAP3204

4-channelLED Driverfor High Brightness LEDs

MagnaChip Semiconductor 

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Datasheet Version 1.5

BOOST OVER-CURRENT PROTECTION

The MAP3204 features Over-Current Protection

(OCP) by sensing CS pin voltage. This CS pin is

used for inductor current sensing for current mode

control as well.

The internal OCP sensing voltage decreases with

increase of gate duty-cycle due to internal slope

compensation which ensures stable CCM operation.

Following graph shows the relationship between

gate duty cycle and internal OCP sensing voltage

DIODE OPEN / OUTPUT SHORT-CIRCUIT

PROTECTION

When OVP pin voltage is less than 0.1V, the

MAP3204 turns off the external MOSFET. This

protects the driver from damage if the output schottky

diode is open(defective or poor solder contact), or

output voltage is short to ground.

TURN-OFF SEQUENCE

To avoid abnormal GATE turn-on at turn-off, PWMI

should be turned-off in advance of EN off.

In order to avoid touching the current limit during

normal operation, the voltage across the current

sensing resistor Rcs should be less than 80% of the

worst case current limit voltage.

RCS

= 0.8 ×

VCS

I L _ PEAK

LED OPEN PROTECTION

In case the voltage on LED current sink pins (FB1~4)

are below LED open protection threshold voltage due to

LED open, the output voltage is boosted up to OVP level.

The MAP3204 automatically ignores the corresponding

channel and remaining string(s) will continue operation.

The operation is resumed recycling the EN pin or

applying a complete power-on-reset(POR).

If all the strings are open, the output voltage remains

between OVP_high and OVP_low level.

LED SHORT PROTECTION

If the voltage at any of the FB1-4 pins exceeds a

threshold of approximately 5.5V due to LED short

during normal operation, the MAP3204 turns off the

corresponding string after LED short protection

time(tscp) and the remaining string(s) will continue

operation. The operation is resumed recycling the EN

pin or applying a complete power-on-reset(POR).

Feb 28th 2012.

7

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