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/FLASH
LED Current
Setup
The EVM board has a built-in timing circuit to generate the necessary signals for torch and flash modes.
The timing circuit sets the length of the flash. After a flash, the timing circuit disables the flash function for
approximately 3.2 s. Pressing the flash button during this 3-s period has no effect. This keeps the average
power dissipation of the LED below the maximum power limitation of the LED.
The FLASH OFF input on J3 can be used to force the LED flash off during a flash sequence. This is
intended to turn the flash off in camera phones while the power amplifier is transmitting. A logic 1 on pin 3
of J3 extinguishes the flash as long as the input is high. This does not reset the timing of the timing circuit.
2.2.5
Test Results
NOTE: CH1 = Enable Signal – pin 1 of J3; CH2 = Flash Signal – Pin 2 of J3; CH4 = LED Current
Figure 1. Timing From LED Off to 700-mA Flash
TPS61059EVM-141
4
SLVU150 – January 2006
