PM6680 STMicroelectronics, PM6680 Datasheet - Page 37

• Manufacturer Part Number: PM6680
• Description: IC CTRLR DUAL STEP DOWN 32VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6680

• Applications: Controller, Notebook Power System
• Voltage - Input: 6 ~ 28 V
• Number Of Outputs: 2
• Voltage - Output: 0.9 ~ 5.5 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• Output Voltage: 5 V, 0.9 V to 5.5 V, 0.9 V to 3.3 V
• Output Current: 0.33 A
• Input Voltage: 5.5 V to 28 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 10 C
• For Use With: 497-6379 - BOARD EVALUATION FOR PM6680A497-6378 - BOARD EVALUATION FOR PM6680497-6425 - BOARD EVAL BASED ON PM6680A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PM6680
7.13.6
Closing the integrator loop
The design of external feedback network depends on the output voltage ripple. If the ripple
is higher than approximately 30 mV, the feedback network (
keep the loop stable.
Figure 36. Circuitry for output ripple compensation
The stability of the system depends firstly on the output capacitor zero frequency. The
following condition should be satisfied:
Equation 23
where k is a design parameter greater than 3 and R
determinates the minimum integrator capacitor value C
Equation 24
where gm = 50 us is the integrator transconductance.
In order to ensure stability it must be also verified that:
Equation 25
OUTPUT
VOLTAGE
Vr
t
COMP PIN
VOLTAGE
D
D
? V
f
L
L
t
sw
C
INT
C
C
R
R
? V
C
>
O
O
O
O
U
U
U
U
INT
k
>
C
C
T
T
T
T
F
F
×
I
I
C
C
R
R
2
L
L
T
T
I
I
I
I
f
N
N
N
N
π
>
Zout
T
T
T
T
×
2
⎛
⎜
⎝
π
f
=
sw
g
×
g
k
V
V
m
m
f
C
C
C
2
C
R
R
R
R
Zout
I
−
O
O
I
N
N
2
1
π
2
1
M
M
T
T
O
O
f
P
P
×
Zout
U
U
T
T
C
×
F
F
B
B
out
out
⎞
⎟
⎠
V
k
×
Vr
OUT
I=gm(V1-Vr)
is the ESR of the output capacitor. It
INT
×
V
V
V
R
Vr
OUT
r
r
:
g
out
g
Figure 35
m
m
+
V
V
1
1
V
V
r
r
+
C
C
-
o
) is usually enough to
o
m
m
P
P
p
p
W
W
Device description
a
a
M
M
r
r
a
a
t
t
o
o
r
r
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