Datasheet
SLUS495H − SEPTEMBER 2001 − REVISED AUGUST 2007
16
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DESIGN PROCEDURE
error amplifier compensation
The total load-share loop unity-gain crossover frequency, f
CO
, should be set at least one decade below the
measured crossover frequency of the paralleled modules previously measured, f
CO(module).
(See Figure 7)
Compensation of the transconductance error amplifier is accomplished by placing the compensation resistor,
R
EAO
, and capacitor, C
EAO
, between EAO and GND. The values of these components is determined using
equations (8) and (13).
C
EAO
+
ǒ
g
M
2p f
CO
Ǔ
ǒ
A
CSA
Ǔǒ
A
V
Ǔǒ
A
ADJ
Ǔ
ǒ
Ť
A
PWR
ǒ
f
CO
Ǔ
Ť
Ǔ
Where:
D g
M
is the transconductance of the error amplifier, typically 14 mS,
D f
CO
is equal to the desired crossover frequency in Hz of the load share loop, typically f
CO
(module)/10,
D A
CSA
is the CSA gain,
D A
V
is the voltage gain,
D A
ADJ
is the gain associated with the adjust amplifier,
D |A
PWR
(f
CO
)| is the measured gain of the power module at the desired load share crossover frequency, f
CO
,
converted to V/V from dB
A
CSA
+
R16
R15
A
V
+
R
SHUNT
R
LOAD
,R
LOAD
+
V
OUT
I
OUT(max)
A
ADJ
+
R
ADJUST
R
SENSE
ǒ
R
ADJUST
) R
SENSE
Ǔ
500 W
Ť
A
PWR
ǒ
f
CO
Ǔ
Ť
+ 10
ǒ
G
MODULE
ǒ
f
CO
Ǔ
20
Ǔ
Where G
MODULE
(f
co
) is the measured value of the gain from Figure 7, at the desired crossover frequency.
Once the C
EAO
capacitor is determined, R
EAO
is selected to achieve the desired loop response:
R
EAO
+
ǒ
1
gm
Ť
A
PWR
ǒ
f
CO
Ǔ
Ť
A
V
A
CSA
A
ADJ
Ǔ
2
*
ǒ
1
2p
ǒ
f
CO
Ǔǒ
C
EAO
Ǔ
Ǔ
2
Ǹ
(8)
(9)
(10)
(11)
(12)
(13)