Datasheet

Vref
VO
R1
R3
C1
C2
R2
CO
5pF
RO
gm
ea
COMP
VSENSE
Type 2A
Type 2B
R3
C1
¦
´ ´ p
OUT ESR
1
z =
C R 2
¦
´ ´ p
OUT L
1
p =
C R 2
ps L
Adc = gm R´
s
1+
2 × z
vo
= Adc
vc
s
1+
2 × p
æ ö
ç ÷
p ¦
è ø
´
æ ö
ç ÷
p ¦
è ø
VO
R
L
VC
fp
fz
Adc
gm
ps
R
ESR
C
OUT
TPS54218
www.ti.com SLVS974B –SEPTEMBER 2009–REVISED JULY 2013
Figure 32. Simple Small Signal Model and Frequency Response for Peak Current Mode Control
(7)
(8)
(9)
(10)
SMALL SIGNAL MODEL FOR FREQUENCY COMPENSATION
The TPS54218 uses a transconductance amplifier for the error amplifier and readily supports two of the
commonly used frequency compensation circuits. The compensation circuits are shown in Figure 33. The Type 2
circuits are most likely implemented in high bandwidth power supply designs using low ESR output capacitors. In
Type 2A, one additional high frequency pole is added to attenuate high frequency noise.
Figure 33. Types of Frequency Compensation
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