AMG-LL9910B Datasheet, PDF (10/15 Pages) alpha microelectronics gmbh – Universal High Voltage Single Channel LED Driver

AMG-LL9910B
Universal High Voltage Single Channel LED Driver
d) Linear Dimming
If the second comparator is provided with a threshold voltage lower than the internal threshold
voltage of the first comparator, the current over the LED can be manually adjusted. This can
be achieved with any analog voltage between 0 and the internal reference voltage (e.g. with a
potentiometer).
e) Digital Dimming
With an external PWM signal at the PWMD pin, the gate driver can be gated. This means, the
LED will light up during the duty cycle of the external PWM signal and vice versa, the LED will
be off during the off-time of the external PWM signal.
The external PWM frequency needs to be much smaller than the frequency of the
AMG-LL9910B. The external PWM frequency should be at least 10x smaller, otherwise
fluctuation effects may occur.
The PWMD pin may also be used to enable or disable the device. The IC is enabled, when
PWMD is pulled to Vcc. It is disabled, when PWMD is pulled to GND:
f) PWM Frequency
FPWM [kHz] = 25000/(Rosc [kΩ]+22)
g) PFC
The AMG-LL9910B does not have a PFC integrated stage. As such, a PFC is usually
necessary for off line LED drivers. This can be either a passive PFC or even an active one,
when the power increases relatively high.
AMG-LL9910B Revision: B
09/13/12
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