Setup
OUT, LED1, LED2, TORCH/TEMP (J13, J10, J22) -
These provide access to the regulated output of the
driver, the outputs of the LED current sources, and the TEMP pin. The user can measure VOUT with
reference to GND, VLED with reference to GND, current source headroom directly between VOUT and
VLED, and can monitor or control TORCH/TEMP input.
VINL/VIN (J7) -
The user can monitor the Inductor Current and Input Current waveforms by omitting this
jumper and using separate wires from the power supply to the VINL and VIN pins. This will remove the
Input Capacitors from the Inductor and eliminate their filtering effect to the Inductor Current.
J17 and J18: LED Current measurements -
The LM3643EVM provides a way to accurately measure the
LED current through both LEDs on board. Resistors R1 & R2 (0.1
Ω
) are placed between the cathode of
LED1 & LED2, respectively, and Ground. The user can first measure the resistor values accurately, by
applying a known current through connector DxF and Ground and measuring the voltage between DxS
and GNDS. Then, during normal flash or torch operation, the voltage measured across the resistor divided
by the resistor value will equal the current through the resistor (and the LED).
2.2
Setup
The input voltage range for the flash driver is 2.5 volts to 5.5 volts. The on-board LEDs or an LED module
should be connected for proper operation.
2.3
Operation
For proper operation of the LM3643EVM, the jumpers should be properly configured. The recommended
setting, using shorting blocks is:
VIO to VIN
EN to VIO
STROBE to PWM0 or external signal
TORCH/TEMP to PWM1 or external signal
TX to PWM2 or external signal
LEDs (J14) shorted
In this configuration, the device will power up when power is applied.
6
LM3643EVM User's Guide
SNVU399 – August 2014
Copyright © 2014, Texas Instruments Incorporated
