Texas Instruments TPS92682EVM, Руководство пользователя, Страница: 13 / 49

VLED1
ISW1
ILED1
VLED1
VLED2+
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Performance Data and Typical Characteristic Curves
13 SLUUC13A – May 2019 – Revised August 2019
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TPS92682EVM Constant Current Two-channel Boost and Boost-to-Battery
5.2 PWM Dimming
Figure 6 shows PWM dimming of the two boost and boost-to-battery channels of the TPS92682EVM-070.
The I
LED
is programmed to its maximum value. A string of 12×LEDs connected to the output of the boost
and 6×LEDs to the output of the boost-to-battery channels. When internal PWM dimming counter is used,
the two channels, by default, have 180
o
phase-shift.
V
IN
= 12 V
Figure 6. CC Boost and Boost-to-Battery PWM Dimming
Figure 7 shows the switch current across the sense resistor at the rising edge of the PWM dimming for the
boost channel.
V
IN
= 12 V, and V
OUT
= 40 V
Figure 7. CC Boost Switch Current Sense
5.3 Faults
TPS92682-Q1 include various fault handling and diagnostic features. Figure 8 and Figure 9 show the LED
short protection for CC boost channel and LED open protection for the boost-to-battery channel.
As shown in Figure 8 , when a short across the LED load occurs, the overcurrent (OC) protection is
triggered (if OC Fault is enabled), the COMP-pin is pulled low, and the associated channel is turned off.
The channel remains off for the programmed main fault timer (MFT), when the channel performs a soft-
start sequence.
As shown in Figure 9 , when open LED load occurs, the load voltage increases above the programmed
overvoltage (OV) threshold, and the associated channel turns off. The channel remains off until the load
voltage drops below a OV hysteresis value, when the channel performs a soft-start sequence. Set the OV
threshold by programming the OV register and the OV detection resistor dividers.