Datasheet

2
(max)
(max)(max)
L
OUTL
I
II
D
+=
÷
÷
ø
ö
ç
ç
è
æ
-= 1
21
REF
OUT
V
V
RR
TPS62140, TPS62140A
TPS62141, TPS62142, TPS62143
SLVSAJ0B –NOVEMBER 2011–REVISED JUNE 2013 www.ti.com
APPLICATION INFORMATION
The following information is intended to be a guideline through the individual power-supply design process.
Programming the Output Voltage
While the output voltage of the TPS62140 is adjustable, the TPS62141/2/3 are programmed to fixed output
voltages. For fixed output versions, the FB pin is pulled down internally and may be left floating. It is
recommended to connect to AGND to improve thermal resistance. The adjustable version can be programmed
for output voltages from 0.9 V to 6 V by using a resistive divider from VOUT to AGND. The voltage at the FB pin
is regulated to 800 mV. The value of the output voltage is set by the selection of the resistive divider from
Equation 6 (see Figure 4). It is recommended to choose resistor values which allow a current of at least 2 µA,
meaning the value of R2 should not exceed 400 kΩ. Lower resistor values are recommended for highest
accuracy and most-robust design. For applications requiring lowest current consumption, the use of fixed output-
voltage versions is recommended.
(6)
In case the FB pin is opened, the device clamps the output voltage at the VOS pin internally to about 7.4 V.
External Component Selection
The external components have to fulfill the needs of the application, but also the stability criteria of the devices
control loop. The TPS6214X is optimized to work within a range of external components. The LC output filters
inductance and capacitance have to be considered in conjunction, creating a double pole, responsible for the
corner frequency of the converter (see Output Filter and Loop Stabilitysection). Table 1 can be used to simplify
the output filter component selection.
Table 1. Recommended LC Output Filter Combinations
(1)
4.7 µF 10 µF 22 µF 47 µF 100 µF 200 µF 400 µF
0.47 µH
1 µH √ √ √ √
2.2 µH √ √
(2)
√ √ √
3.3 µH √ √ √ √
4.7 µH
(1) The values in the table are nominal values.
(2) This LC combination is the standard value and recommended for most applications.
spacing
TPS6214X can be run with an inductor as low as 1 µH or 2.2 µH. FSW should be set Low in this case. However,
for applications running with the low-frequency setting (FSW = High) or with low input voltages, 3.3 µH is
recommended. More detailed information on further LC combinations can be found in SLVA463.
Inductor Selection
The inductor selection is affected by several effects like inductor ripple current, output ripple voltage, PWM-to-
PSM transition point, and efficiency. In addition, the inductor selected must be rated for appropriate saturation
current and dc resistance (DCR). Equation 7 and Equation 8 calculate the maximum inductor current under static
load conditions.
spacing
(7)
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