AMG-LL9910B Datasheet, PDF (8/15 Pages) alpha microelectronics gmbh – Universal High Voltage Single Channel LED Driver

AMG-LL9910B
Universal High Voltage Single Channel LED Driver
9. Application
9.1. Example Application Circuit
Vin DC
Vin
Vdd
LD ^AMG
LL9910B
PWMD
Gate
Rosc
CS
GND
Figure 3: Buck LED Driver
9.2. Application Notes
a) Peak Current Regulation
The oscillator resistor sets the PWM frequency. After each oscillator period, the gate driver is
pulled high and the duty cycle begins.
When the current over sense resistor RCS reaches the current limit, the current sense
comparator will trip and after blanking time the gate driver output is pulled low and the duty
cycle ends.
Smaller inductors and lower PWM frequencies will provide for higher current ripple. In the
case that the highest light intensity is desired, the ripple should be maximized and the LED
driven to it's specified peak current limit.
In the case that the highest efficacy and longest LED lifetime is desired, the LED needs to be
driven to the optimum current value only. In this situation, the ripple should be kept as low as
possible. Bigger inductor values and higher PWM frequencies will help achieve this result.
AMG-LL9910B Revision: B
09/13/12
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