Datasheet

OUT
FB
V
R1 = R2 × - 1
V
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TPS63020
TPS63021
SLVS916C –JULY 2010–REVISED MARCH 2013 www.ti.com
Table 2. Inductor Selection
VENDOR INDUCTOR SERIES
Coilcraft XFL4020
Toko FDV0530S
Capacitor selection
Input Capacitor
At least a 10μF input capacitor is recommended to improve transient behavior of the regulator and EMI behavior
of the total power supply circuit. A ceramic capacitor placed as close as possible to the VIN and PGND pins of
the IC is recommended.
Output Capacitor
For the output capacitor, use of a small ceramic capacitors placed as close as possible to the VOUT and PGND
pins of the IC is recommended. If, for any reason, the application requires the use of large capacitors which can
not be placed close to the IC, use a smaller ceramic capacitor in parallel to the large capacitor. The small
capacitor should be placed as close as possible to the VOUT and PGND pins of the IC. The recommended
typical output capacitor value is 30µF with a variance that depends on the specific application requirements.
There is also no upper limit for the output capacitance value. Larger capacitors will cause lower output voltage
ripple as well as lower output voltage drop during load transients.
When choosing input and output capacitors, it needs to be kept in mind, that the value of capacitance
experiences significant losses from their rated value depending on the operating temperature and the operating
DC voltage. It's not uncommon for a small surface mount ceramic capacitor to lose 50% and more of it's rated
capacitance. For this reason could be important to use a larger value of capacitance or a capacitor with higher
voltage rating in order to ensure the required capacitance at the full operating voltage.
Bypass Capacitor
To make sure that the internal control circuits are supplied with a stable low noise supply voltage, a capacitor can
be connected between VINA and GND. Using a ceramic capacitor with a value of 0.1μF is recommended. The
value of this capacitor should not be higher than 0.22μF.
Setting the Output Voltage
When the adjustable output voltage version TPS63020 is used, the output voltage is set by the external resistor
divider. 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 8V. 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 0.01μA, and the voltage across the resistor between
FB and GND, R
2
, is typically 500 mV. Based on these two values, the recommended value for R2 should be
lower than 500kΩ, in order to set the divider current at 1μA or higher. It is recommended to keep the value for
this resistor in the range of 200kΩ. From that, the value of the resistor connected between VOUT and FB, R1,
depending on the needed output voltage (V
OUT
), can be calculated using Equation 4:
(4)
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