PM6652 STMicroelectronics, PM6652 Datasheet - Page 44

• Manufacturer Part Number: PM6652
• Description: IC CTLR STEPDOWN SMPS 32VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6652

• Applications: Controller, Intel IMVP-6.5™, VR11
• Voltage - Input: 4.5 V ~ 36 V
• Number Of Outputs: 1
• Voltage - Output: 0.3 V ~ 1.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application ideas
9
9.1
44/53
Application ideas
Load transient response improvement with feedback
capacitor
Referring to
can be improved by adding the feedback capacitor C34. So doing the performed load line,
starting from Equation 8, can be computed again:
Equation 31
The sensed current information is still given by:
Equation 32
By joining the two previous results, the complete droop equation becomes:
Equation 33
In order to get an almost flat droop function, from DC to high frequency, and a “squared”
load transient response, the above equation requires two conditions:
●
●
If R
is bigger compared to what can be sensed when the feedback capacitor is not mounted.
This feature can be very helpful when low DCR inductors are used and the sensed current
ripple, CSNS-VOUT, is lower than about 10 mV
In order to avoid any output voltage undershoots during load transient the above mentioned
conditions should be translated into:
●
●
The two components used to fine tune the load transient response are C
the other components are fixed when the droop is programmed and the inductor has already
been selected.
17
C
C
C
C
>R
34
34
34
15
R
*R
*R
14
*R
*R
DROOP
R
R
R
C
17
17
17
A
(typical application), C
DROOP
A
B
SNS
//R
Figure 2 on page 7
=L/R
//R
≥L/R
=
=
B
R
=
R
14
−
≥C
33
31
⎛
⎜ ⎜
⎝
DCR
V
DCR
=C
( )
1
s
OUT
34
+
+
15
=
*R
R
R
R
*R
G
34
17
14
=
17
D
A
R
⎞
⋅ ⎟ ⎟
⎠
//R
( )
//R
s
A
R
R
14
⋅
+
B
R
B
A
Doc ID 16867 Rev 3
R
R
SNS
, the droop gain network made by R14, R15, R17 and R18
+
B
B
R
15
⋅
( )
B
R
*R
s
DCR
⋅
R
A
=
DCR
//R
⎛
⎜ ⎜
⎝
1
⋅
1
+
B
+
⋅
< L/R
R
R
1
s
17
14
+
⋅
1
1
R
PP
s
+
⎞
⋅ ⎟ ⎟
⎠
+
DCR
A
⋅
.
R
C
⎛
⎜
⎜
⎝
s
//
1
sL
DCR
34
⋅
R
C
+
so the high frequency sensed current
B
⋅
1
34
s
R
+
⋅
⋅
17
C
⋅
C
s
R
15
34
⋅
//
17
C
R
⋅
⋅
34
i
R
14
L
( )
17
⋅
s
R
⋅
1
//
17
=
+
R
R
s
14
SNS
⋅
1
C
⎞
⋅ ⎟ ⎟
⎠
+
15
34
( ) ( )
R
R
s
sL
SNS
DCR
⋅
and C
R
⋅
i
L
A
( )
s
s
//
R
15
B
PM6652
, since