TPS629210-Q1 has a MODE/S-CONF pin
which can be used to customize the device behavior. Refer to schematic in Figure 2-2 and Figure 2-3
- Selects device configuration
(switching frequency, internal or external feedback, output discharge, Forced
PWM and Auto PFM/PWM mode) by connecting a single resistor between this pin and
-VOUT (IC GND pin) or connecting directly to VIN or
-VOUT (IC GND pin).
- A 2.5 MHz switching
frequency setting is recommended for inverting buck-boost application
due to lower inductor ripple current. The design example selects
MODE/S-CONF resistor as 27.4 k which configures internal feedback, 2.5
MHz switching frequency, Auto PFM/PWM with AEE and output discharge
enabled.
- Note that the maximum
output current will be reduced while using 2.2uH inductor and 1MHz
switching frequency. 3.3 uH or larger inductance is strongly recommended
for 1 MHz switching frequency configuration, otherwise special care has
to be taken to make sure the half ripple current doesn't trip the
negative current limit under no load condition.
- Dynamic MODE option is an advance
feature which allows MODE/S-CONF pin to actively switch between Forced PWM and
Auto PFM/PWM during operation. This feature provides user with the option of
controlling when/if the device enters power save mode (DCM). In the inverting
buck-boost topology, VIN is HIGH and -VOUT is LOW, but
this is only possible by driving the MODE/S-CONF pin between VIN and
-VOUT. This can be done with the same type of circuit used to
drive the EN pin HIGH and LOW as shown in Figure 2-1
- The external feedback
configuration shown in Figure 2-3 , where the MODE/S-CONF pin can be tied to -VOUT directly to
configure as 2.5 MHz switching frequency, Auto PFM/PWM with AEE and output
discharge enabled.