QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
1268A-A, 1268A-B
HIGH VOLTAGE LED CONTROLLER
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Figure 1. Test procedure setup drawing for DC1268A-A and DC1268A-B
TWO ICS, THREE TOPOLOGIES
DC1268A features two build versions. DC1268A-A
uses the LT3755EUD with an open LED status and
DC1268A-B uses the LT3755EUD-1 with sync. Each
board is clearly marked indicating which IC is used.
The schematic for each is attached to this docu-
ment. The open LED indicator terminal has a pull-
up resistor to the internal 7V regulator IntVcc. The –
B version with the sync terminal has an RC filter
between the PWM input pin and the SYNC input
pin. This filter provides a small delay between the
PWM signal and the SYNC input when PWM is
used in order to optimize high PWM dimming ratio
waveforms. If high ratios are not needed, this RC
filter may not be needed. If the sync input is used,
this filter may be removed. Please note that when
PWM and SYNC are both used, optimal PWM dim-
ming occurs when there is at least a 200ns delay