Datasheet

V
out
+ 1.146 V
ƪ
1 )
R1
R2
ƫ
R1
430 kΩ
SW
SW
FB1
SUP
C2+
C2−/MODE
D1
C8
6.8 pF
C4
22 µF
C2
0.22 µF
R2
56 kΩ
V
O
1
Up to 10 V/150 mA
ƒ
z
+
1
2 p C8 R1
Load Step
TPS65100-Q1
www.ti.com SLVS849A –JULY 2008–REVISED APRIL 2012
Design Procedure Quick Steps
1. Select the feedback resistor divider to set the output voltage.
2. Select the feedforward capacitor to place a zero at 50 kHz.
3. Select the compensation capacitor on pin COMP. The smaller the value, the higher the low frequency gain.
4. Use a 50-kΩ potentiometer in series to C
c
and monitor V
out
during load transients. Fine tune the load
transient by adjusting the potentiometer. Select a resistor value that comes closest to the potentiometer
resistor value. This needs to be done at the highest V
in
and highest load current since the stability is most
critical at these conditions.
Setting the Output Voltage and Selecting the Feedforward Capacitor
The output voltage is set by the external resistor divider and is calculated as:
Across the upper resistor a bypass capacitor is required to speed up the circuit during load transients as shown
in Figure 15.
Figure 15. Feedforward Capacitor
Together with R1 the bypass capacitor C8 sets a zero in the control loop at approximately 50 kHz:
A value closest to the calculated value should be used. Larger feedforward capacitor values reduce the load
regulation of the converter and cause load steps as shown in Figure 16.
Figure 16. Load Step Caused By A Too Large Feedforward Capacitor Value
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Product Folder Link(s): TPS65100-Q1