Texas Instruments TPS92682EVM, User Manual, Page: 40 / 49

u
u
LED
CS
VIADJ 0.171
I
255 R
TPS92682EVM-70 Power UP and Operation
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40 SLUUC13A – May 2019 – Revised August 2019
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TPS92682EVM Constant Current Two-channel Boost and Boost-to-Battery
Figure 50. Devices Window
Apply the settings shown in Figure 51 .
1. Select the Internal PWM box to set the PWM dimming to internal.
2. To set the switching frequency, f
SW
to 400kHz, do not change the Channel Clock Div from the default
value of 2.
3. Enter the Channel 1 and Channel 2 Soft Start value to 100 .
4. Enter the desired value for the CH1 and CH2 V/I Adjust DAC. This DAC controls the I
LED
current. For
TPS92682EVM-070, the DAC maximum value of 255 corresponds with an I
LED
of approximately 570
mA. The relation between I
LED
and the DAC value is shown in Equation 1 .
where
• R
CS
is the current sense resistor (R3 for channel-1 and R20 for channel-2) (1)
5. The EVM generates the internal PWM using a 10-bit DAC counter. Set the PWM duty cycle to a value
between zero and 1023 for PWM dimming. In order to turn on the LEDs with 100% duty cycle, set the
PWM DAC value to 1023.
6. By default CHx-Slope is set to code "5", which corresponds to 250 mV of peak slope. For the
TPS92682EVM-70, it is recommended to set the slopes for both channels to a code "1” or "2" as
shown in
Figure 51