LT3595
APPLICATIONS INFORMATION
Dimming Control
The sixteen PWM1-16 inputs control the dimming func-
tion. Each channel is modulated by its corresponding
PWM1-16 input. On a rising edge of any PWM1-16, the
IC’s internal support circuitry is enabled and the specific
channel turns on. LED current flows in the channel until
the falling edge of the PWM1-16 input. In this way, the
average LED current is modulated. The minimum on time
of a channel is 2μs and the maximum period is 10ms (at
100Hz). Therefore, the maximum dimming ratio is 5000:1.
Since the maximum R
SET
produces 10mA, the minimum
modulated LED current is 2μA.
When multiple channels are modulated, the rising edges
of PWM1-16 must be synchronized. The falling edges may
be asynchronous. A sample timing diagram is shown in
Figure 3.
SYNCHRONIZED RISING EDGES
PWM1-4
t
ON(MIN)
= 2μs
PWM5-8
t
MAX
= 10ms
PWM9-16
I
LED1-4
I
LED5-8
I
LED9-16
3595 F03
Figure 3. Timing Diagram for Multi-Channel Modulation
3595f
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