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)
L1
VIN
VINA
EN
PS/SYNC
GND
L2
VOUT
FB
PGND
L1
R1
R2
C2
R3
C3
C1
V
IN
V
OUT
TPS6300X
INDUCTOR SELECTION
TPS63000
TPS63001
TPS63002
SLVS520B – MARCH 2006 – REVISED JULY 2008 ........................................................................................................................................................... www.ti.com
The TPS6300x 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 TPS6300x is
used.
Within the TPS6300X family there are fixed and adjustable output voltage versions available. To properly
configure the fixed output voltage devices, the FB pin is used to sense the output voltage. This means that it
must be connected directly to VOUT. At the adjustable output voltage versions, 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 500mV. The maximum
recommended value for the output voltage is 5.5V. 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 500k Ω , 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 200k Ω . 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 Ω resistor should be chosen for R
1
. To improve
control performance using a feedforward capacitor in parallel to R
1
is recommended. The value for the
feedforward capacitor can be calculated using Equation 2 .
Figure 19. Typical Application Circuit for Adjustable Output Voltage Option
To properly configure the TPS6300X devices, an inductor must be connected between pin L1 and pin L2. To
estimate the inductance value Equation 3 and Equation 4 can be used.
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