Datasheet

F
DROOPZ
+
1
2p
ǒ
V
DROOP
I
OUT(max)
Ǔ
C
OUT
C2 +
C1
2p R2 C1
ǒ
F
DROOPZ
* 1
Ǔ
GAIN AND PHASE
vs
FREQUENCY
G - Gain - dB
Phase - °
f - Frequency - Hz
60
0
10
20
40
50
30
-20
-10
0
60
80
20
40
-20
100 1 k 10 k 100 k 1 M
Phase
Gain
V
IN
= 12 V
V
OUT
= 1.5 V
I
OUT
= 100 A
TPS40090
TPS40091
SLUS578B –OCTOBER 2003– REVISED MAY 2006 www.ti.com
The droop function, as well as the output capacitor ESR, introduces zero on some frequency left of the crossover
point.
(12)
To compensate for this zero, pole on the same frequency should be added to the error amplifier transfer function.
With Type II compensation network a new value for the capacitor C2 is required compared to the case without
droop.
(13)
When attempting to close the feedback loop at frequency that is near the theoretical limit, use the above
considerations as a first approximation and perform on bench measurements of closed loop parameters as
effects of switching frequency proximity and finite bandwidth of voltage and current amplifiers may substantially
alter them as it is shown in Figure 9.
Figure 9.
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