Datasheet

R k f
OSC
( ) = 174W ·
-1.122
TPS65250
www.ti.com SLVSAA3C –JUNE 2010–REVISED OCTOBER 2012
Table 1. Storage and Release Circuit Advantages (continued)
FEATURE ADVANTAGE
Using a resistor to set the peak current limit allows to choose the
Adjustable current limit smallest possible inductor for a given load condition by setting the
current limit to match the saturation current of the inductor.
TPS65250 can be synchronized to a 1.1-MHz or 2.2-MHz external
Adjustable frequency and sync pin clock. The Sync pin is blanked time equal to the PGOOD delay
plus 0.5 s to allow for external low clock setting.
In low power mode device takes less than 20 mW with a 12-V
Low power mode input. If an step load > 100 mA is applied to any of the converters,
its output will switch to PWM mode.
Two LDOS rated 3.3 V, 10 mA and 6.5 V, 10 mA are available as
Always on LDOs
long as input supply is higher than UVLO threshold.
Integrated fets in all converters plus integrated driver circuits for
storage and release, minimize the real state required by power
Reduced footprint
stage. Selectable frequency allow to reduce size of inductor plus
input/output capacitors.
All rails are monitored and a Power Good signal is issued after an
Voltage supervisor and reset generator
adjustable time-out elapses.
DETAILED DESCRIPTION
Adjustable Switching Frequency
To select the internal switching frequency connect a resistor from ROSC to ground. Figure 30 shows the required
resistance for a given switching frequency.
Figure 30. ROSC vs Switching Frequency
(1)
For operation at 800 kHz a 230-kΩ resistor is required.
Synchronization
The status of the SYNC pin will be ignored during start-up and the TPS65250’s control will only synchronize to
an external signal after the PGOOD signal is asserted. The status of the SYNC pin will be ignored during start-up
and the TPS65250 will only synchronize to an external clock if the PGOOD signal is asserted. When
synchronization is applied, the PWM oscillator frequency must be lower than the sync pulse frequency to allow
the external signal trumping the oscillator pulse reliably. When synchronization is not applied, the SYNC pin
should be connected to ground.
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