Datasheet

O ESR
1
z =
C R 2
¦
´ ´ p
O L
1
p =
C R 2
¦
´ ´ p
ps L
Adc = gm R´
s
1+
2 z
VOUT
= Adc
VC
s
1+
2 p
æ ö
ç ÷
´ ¦
è ø
´
æ ö
ç ÷
´ ¦
è ø
p
p
VOUT
R
ESR
C
O
R
L
VC
gm
ps
fp
fz
Adc
VOUT
R
ESR
C
O
R
L
VC
gm
ps
TPS54622
SLVSA70B –MARCH 2011–REVISED JANUARY 2014 www.ti.com
Figure 26. Simplified Small Signal Model for Peak Current Mode Control
Figure 27. Simplified Frequency Response for Peak Current Mode Control
(10)
(11)
(12)
(13)
Where
gm
ea
is the GM amplifier gain ( 1300μA/V)
gm
ps
is the power stage gain (16A/V).
R
L
is the load resistance
C
O
is the output capacitance.
R
ESR
is the equivalent series resistance of the output capacitor.
Small Signal Model for Frequency Compensation
The device uses a transconductance amplifier for the error amplifier and readily supports two of the commonly
used Type II compensation circuits and a Type III frequency compensation circuit, as shown in Figure 28. In
Type 2A, one additional high frequency pole, C6, is added to attenuate high frequency noise. In Type III, one
additional capacitor, C11, is added to provide a phase boost at the crossover frequency. See Designing Type III
Compensation for Current Mode Step-Down Converters (SLVA352) for a complete explanation of Type III
compensation.
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