Datasheet

APPLICATION INFORMATION
Design Procedure
Programming the Output Voltage
R
1
+ R
2
ǒ
V
OUT
V
FB
* 1
Ǔ
(1)
C
ff
+
2.2 ms
R
1
(2)
TPS63000-Q1
SLVS968 JUNE 2009 ......................................................................................................................................................................................................
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The TPS63000 dc/dc converters are intended for systems powered by one-cell Li-Ion or Li-Polymer battery with a
typical voltage between 2.3 V and 4.5 V. They can also be used in systems powered by a double or triple cell
Alkaline, NiCd, or NiMH battery with a typical terminal voltage between 1.8 V and 5.5 V . Additionally, any other
voltage source with a typical output voltage between 1.8 V and 5.5 V can power systems where the TPS63000 is
used.
An external resistor divider is used to adjust the output voltage. The resistor divider must be connected between
VOUT, FB, and GND. When the output voltage is regulated properly, the typical value of the voltage at the FB
pin is 500 mV. The maximum recommended value for the output voltage is 5.5 V. The current through the
resistive divider should be about 100 times greater than the current into the FB pin. The typical current into the
FB pin is 0.01 µ A, and the voltage across the resistor between FB and GND, R
2
, is typically 500 mV. Based on
those two values, the recommended value for R
2
should be lower than 500 k , in order to set the divider current
at 1 µ A or higher. It is recommended to keep the value for this resistor in the range of 200 k . From that, the
value of the resistor connected between VOUT and FB, R
1
, depending on the needed output voltage (V
OUT
), can
be calculated using Equation 1 :
If as an example, an output voltage of 3.3 V is needed, a 1.0-M resistor should be chosen for R
1
. To improve
control performance, using a feed-forward capacitor in parallel to R
1
is recommended. The value for the
feed-forward capacitor can be calculated using Equation 2 .
Figure 3. Typical Application Circuit for Adjustable Output Voltage Option
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