Datasheet

Short-Circuit Protection
Thermal Shutdown
Input Capacitor Selection
Output Filter Design (Inductor and Output Capacitor)
ƒ =
c
2 xL xCp
O
2 x2.2 Hx22 Fp m m
=22.8kHz
1 1
=
(6)
TPS62510
SLVS651A – MAY 2006 – REVISED JULY 2009 ................................................................................................................................................................ www.ti.com
The TPS62510 monitors the forward current through both the high-side and low-side power devices. This
enables the converter to limit the short-circuit current, which helps to protect the device and other circuits
connected to its output.
As soon as the device's junction temperature exceeds 160 ° C (typical), all switching activity ceases and both
high-side and low-side power transistors are off. The device continues operation once the temperature fall to
20 ° C (typical) below its thermal shutdown threshold of 160 ° C.
Because of the nature of the buck converter having a pulsating input current, a low ESR input capacitor is
required for best input voltage filtering, and minimizing the interference with other circuits caused by high input
voltage spikes. The converter needs a ceramic input capacitor of 22 µ F. The input capacitor may be increased
without any limit for better input voltage filtering. The AVIN pin is separated from the power input of the converter.
Note that the filter resistor may affect the undervoltage lockout threshold since up to 5 mA can flow via this
resistor into the AVIN pin when the converter runs in PWM mode.
Table 1. Input Capacitor Selection
Capacitor Value Case Size Component Supplier Comments
22 µ F 1206 TDK C3216X5R0J226M Ceramic
22 µ F 1206 Taiyo Yuden JMK316BJ226ML Ceramic
The TPS62510 step-down converter has an internal loop compensation. Therefore, the external L-C filter must
be selected to work with the internal compensation.
The internal compensation is optimized to operate with an output filter of L = 2.2 µ H with an output capacitor of
C
O
= 22 µ F. The output filter has its corner frequency per Equation 6 :
with
L = 2.2 µ H
C
O
= 22 µ F
As a general rule of thumb, the product LxC should not move over a wide range when selecting a different output
filter. This is because the internal compensation is designed to work with a certain output filter corner frequency,
as calculated in Equation 6 . This is especially important when selecting smaller inductor or output capacitor
values that move the corner frequency to higher frequencies. However, when selecting the output filter a low limit
for the inductor value exists due to other internal circuit limitations. The minimum inductor value for the
TPS62510 should be kept at 2.2 µ H. Selecting a larger capacitor value is less critical because the corner
frequency drops, causing fewer stability issues.
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