Datasheet

COMP
CO
R7 51.1k
R4 R7 K 18.2k
K 2.80
W
= ´ = = = W
f
L
10 10
C2 2837pF
2 R4 2 30kHz 18.7k
= = =
p ´ ´ p ´ ´ W
f
L
1 1
C4 56.74pF
10 R4 10 30kHz 18.7k
» = =
p ´ ´ p ´ ´ W
1 1
C4 11.35pF
GBW R4 1.5MHz 18.7k
> = =
p ´ ´ p ´ ´ W
6
SS SS
C 20 T 10
-
= ´ ´
TPS40210-Q1, TPS40211-Q1
www.ti.com SLVS861D –AUGUST 2008–REVISED APRIL 2010
To set the mid-band gain of the error amplifier to K
COMP
use Equation 63.
(63)
R4 = 18.7 kΩ selected.
Place the zero at 10th the desired cross-over frequency.
(64)
C2 = 2200 pF selected.
Place a high-frequency pole at about five times the desired cross-over frequency and less than one-half the unity
gain bandwidth of the error amplifier:
(65)
(66)
C4 = 47 pF selected.
R-C Oscillator
The R-C oscillator calculation as shown in Equation 5 substitutes 100 for C
T
and 600 for f
SW
. For a 600-kHz
switching frequency, a 100-pF capacitor is selected and a 262-kΩ resistor is calculated (261 kΩ selected).
Soft-Start Capacitor
Because VDD > 8 V, the soft-start capacitor is selected by using Equation 67 to calculate the value.
(67)
For T
SS
= 12 ms, C
SS
= 240 nF, a 220-nF capacitor selected.
Regulator Bypass
A regulator bypass capacitor of 1.0-mF is selected per the recommendation.
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Product Folder Link(s): TPS40210-Q1 TPS40211-Q1