PM6680ATR STMicroelectronics, PM6680ATR Datasheet - Page 37

• Manufacturer Part Number: PM6680ATR
• Description: IC CTRLR DUAL STEP DOWN 32VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6680ATR

• Applications: Controller, Embedded Computer System
• Voltage - Input: 6 ~ 36 V
• Number Of Outputs: 2
• Voltage - Output: 0.9 ~ 5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• 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
• Other names: 497-6896-2; PM6680ATR

PM6680A
Figure 37. Virtual ESR network
The T node voltage is the sum of the output voltage and the triangular waveform generated
by the virtual ESR network. In fact the virtual ESR network behaves like a further equivalent
ESR.
A good trade-off is to design the network in order to achieve an R
Equation 28
where ∆IL is the inductor current ripple and V
voltage. It should be chosen higher than approximately 30 mV.
The new closed loop gain depends on C
that:
Equation 29
Where:
∆V
∆V
Output
Output
voltage
voltage
D
D
D
D
∆V
∆V
t
t
1
1
R1
R1
R1
R1
C
C
C
C
T node
T node
voltage
voltage
L
L
L
L
T
T
R
R
R
R
t
t
R
R
C
C
R
R
C
C
R
COMP pin
COMP pin
voltage
voltage
C
R
R
R
R
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
ESR
INT
C
C
INT
INT
C
C
INT
INT
Vr
Vr
FILT
FILT
FILT
FILT
>
INT.
=
2
V
π
t
t
g
RIPPLE
In order to ensure stability it must be verified
∆
×
RIPPLE
m
I
f
L
∆V
∆V
C
C
C
C
Z
INT
INT
INT
INT
×
1
1
R
R
R
R
R
R
R
R
R
R
R
R
−
V
2
2
2
1
1
1
2
2
2
1
1
1
COMP
COMP
COMP
COMP
Vr
is the overall ripple of the T node
OUT
R
OU
OU
T
T
OU
OU
T
T
out
FB
FB
FB
FB
Vr
Vr
Vr
Vr
gm
gm
gm
gm
ESR
+
+
V1
V1
V1
V1
given by:
Vr
Vr
Vr
Vr
Design guidelines
+
+
Comparator
Comparator
Comparator
Comparator
-
-
PWM
PWM
PWM
PWM
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