Datasheet

C
C
= 4.7 nF
f
z
+
1
2 p Cc Rc
VIN
COMP
R
C
15 kΩ
C
C
1 nF
Load Step
TPS65140, TPS65141
TPS65145
SLVS497E –SEPTEMBER 2003–REVISED NOVEMBER 2012 www.ti.com
Figure 16. Load Step Caused By A Too Large Feedforward Capacitor Value
Compensation
The regulator loop can be compensated by adjusting the external components connected to the COMP pin. The
COMP pin is connected to the output of the internal transconductance error amplifier. A typical compensation
scheme is shown in Figure 17.
Figure 17. Compensation Network
The compensation capacitor C
c
adjusts the low frequency gain, and the resistor value adjusts the high frequency
gain. The following formula calculates at what frequency the resistor increases the high frequency gain.
Lower input voltages require a higher gain and a lower compensation capacitor value. A good start is C
c
= 1 nF
for a 3.3-V input and C
c
= 2.2 nF for a 5-V input. If the device operates over the entire input voltage range from
2.7 V to 5.8 V, a larger compensation capacitor up to 10 nF is recommended. Figure 18 shows the load transient
with a larger compensation capacitor, and Figure 19 shows a smaller compensation capacitor.
Figure 18. C
C
= 4. 7 nF
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