Datasheet

BAT
DC_IN
USB
Operating Procedure www.ti.com
4 Operating Procedure
The TPS22933A will select the highest input voltage from BAT, USB and DC_IN to source the LDO. The
CAP pin can be used to monitor the selection process. As one input pin becomes higher (typically 150mV)
than the input currently driving the LDO, that input is selected to source the LDO. The CAP pin will change
from the original voltage to the new higher voltage. Figure 4 and Figure 5 show examples of the transfer in
LDO sourcing.
Figure 4. Voltage Changeover Figure 5. CAP Voltage During Switchover
Figure 4 shows the BAT pin (4.2V) controlling the LDO until the DC_IN supply overtakes the BAT voltage
on its way to 5V. The CAP pin follows DC_IN up to 5V. As the DC_IN pin falls below BAT, the CAP pin
goes back to the BAT voltage. Note that LOUT (at 3.6V) in unaffected by the changeover.
Figure 6. TPS22933A with Varying Inputs and CAP Figure 7. TPS22933A with Varying Inputs and Stable
LOUT
6
Using the TPS22933AEVM-005 Triple-Input Power Multiplexer with Auto-Select SLVU589– October 2011
and Integrated LDO
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