The
On Time
slide adjust CHxTON registers which controls the switching frequency of the constant current LED
buck driver, see
. The default value is 7 (decimal) which coincides with a 437-kHz switching
frequency. The switching frequency ranges from 100 kHz to 2,200 kHz, see the
Switching Frequency and
Adaptive On-Time Control
section of the
for detailed calculations. The EVM is
optimized to operate at the default switching frequency.
0
62
Figure 6-17. On Time Slide Bar for Changing Switching Frequency
The
PWM
slide adjusts the internal 10 bit PWM duty cycle (CHxPWM registers) from 0 to 1023, which coincides
with 0 (off) and 1023 (full ON), see
. For example, if you want to operate at a 50% duty cycle slide the
bar to 512 (decimal value), which is half of the full scale of 1024 or 50%. The
PWM Source Internal
box much
be selected for the PWM slide bar setting to be implemented. The
PWM Source Internal
box sets the
CHxINTPWM bit high and enables the use of the internal PWM registers to generate the PWM function for that
channel.
0
1023
Figure 6-18. Internal PWM Duty Cycle Slide Bar
The
Enable
box set the CHxEN bit to 1 for that channel, which means the associated channel is turned on, see
Figure 6-19. Channel Feature Selection Boxes
The
PWM Source Internal
controls the CHxINTPWM register. If the box is selected then the device uses the
register settings for
PWM
slide bar to determine the PWM duty cycle and uses the PWMDIV register to set the
PWM frequency. Note that the PWM frequency (PWMDIV register) sets the frequency for both channels. If this
box is not selected then then the device does PWM dimming based on the signal seen on the UDIM x pins for
each respective channel. The frequency and duty cycle are independent.
The
Low iLimit Resp
,
High iLimit Resp
, and
Therm Response
buttons coincide with setting the device to auto-
restart after a fault time (IFT register setting) has elapsed or if it will latch off when the fault occurs. If box is
selected then the device will latch off when the fault occurs and then reset the EN bit to the default of 0 (off) and
will only continue to run when the EN bit is set to 1 (enabled).
TPS92520EVM-133 Power UP and Operation
SLUUCC4 – OCTOBER 2020
TPS92520EVM-133 Dual 1.6-A Synchronous Buck LED Driver Evaluation
Module
45
Copyright © 2020 Texas Instruments Incorporated
