Texas Instruments TPS650250EVM-447 Evaluation Module TPS650250EVM-447 TPS650250EVM-447 데이터 시트
제품 코드
TPS650250EVM-447
3
Modifications
3.1
Voltage Scaling for DCDC3
(
)
(
)
OUTDCDC_2
R10 VREF
Rx
V
VREF
´
=
-
(1)
(
)
(
)
R11 Rx
R8
R11
Rx
´
=
-
(2)
Modifications
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The output voltage of DCDC3 is externally adjustable with the resistor divider network R10 and R11.
The factory EVM configuration is R10 = 182k and R11 = 182k, resulting in an output voltage of 1.2V.
See the TPS650250 data sheet (
) for assistance on changing the output voltage.
DCDC3 has no preset default output voltages as DCDC1 and DCDC2.
There is a voltage scaling circuit on the EVM, so the output voltage of DCDC3 can be switched between
two voltages. This feature is very useful in order to reduce the power consumption of an application
processor in Low Power Mode.
two voltages. This feature is very useful in order to reduce the power consumption of an application
processor in Low Power Mode.
The voltage scaling circuit consist of JP5,Q1, R7 and R8. The circuit uses a transistor (Q8) to connect a
resistor (R8) in parallel to the lower resistor of the feedback network (R11) of DCDC3.
resistor (R8) in parallel to the lower resistor of the feedback network (R11) of DCDC3.
In factory configuration the components JP5, Q1, R7 and R8 are not assembled on the board.
The EVM has a SOT23 footprint for Q1, so any SOT23 transistor can be used.
Note:
Modifying the resistor network by paralleling R11 and R8 will reduce the overall resistance of
the lower resistor and therefore increase the output voltage of the DCDC converter. See
the lower resistor and therefore increase the output voltage of the DCDC converter. See
and
to design R8.
With:
1.
R10: Upper resistor of the feedback driver
2.
R11: Lower resistor of the feedback driver
3.
Rx = R8
R11
4.
V
OUTDCDC2
: Output voltage when scaling circuit active
5.
VREF: Reference voltage
Figure 1. Voltage Scaling Circuit
Using the TPS650250EVM Power Management IC for Li-Ion Powered Systems
4
SLVU290 – July 2009