MAP3204 Просмотр технического описания (PDF) - MagnaChip Semiconductor

Номер в каталоге

Компоненты Описание

производитель

MAP3204

4-channelLED Driverfor High Brightness LEDs

MagnaChip Semiconductor 

OPERATION TIMING CHART

Confidential

Datasheet Version 1.5

After the enable turns on, the internal 5V LDO is powered up and the internal oscillator starts oscillation. If the PWMI

signal remains low at the initial state, the gate drive output to the external MOSFET also remains low, so the boost

controller dose not step up the output voltage. As soon as the PWMI signal turns on over than at least 1% duty cycle at

fPWMI=1kHz, the controller performs soft-start and continues regulation throughout the PWMI on duty. In the meantime

each FB’s are turned on simultaneously and the constant current flows the LEDs. The timing between PWMI and FB is

approximately same.

The MAP3204 boosts the output voltage only in condition that Vcc is applied and EN and PWMI is turned-on. And it is

guaranteed that there is no abnormal operation with regard to turn-on sequence. But in case that Vcc(Vin) is applied

lastly after EN and PWMI is turned-on, the start-up current is increased because the output voltage is boosted from 0V to

OVP level.

If the PWMI signal remains low state over than 16.4ms at 500kHz boost switching frequency during normal operation,

the controller regards it as dim-zero condition. Because of discharge of output capacitor through the OVP sensing

resistors during the dim-zero time, the output voltage getting declined. So the controller performs soft-start to boost the

output voltage until it reaches the over-voltage-protection level with regarding the dimming duty cycle as 100%. For this

reason, some extra switching can be seen when the on duty of PWMI signal is less than the internal boost on period.

Feb 28th 2012.

8

Share Link: