ADP3168 Analog Devices, ADP3168 Datasheet - Page 20

• Manufacturer Part Number: ADP3168
• Description: 4-Phase Synchronous Buck Controller
• Manufacturer: Analog Devices

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ADP3168
The first step is to compute the time constants for all of the poles and zeros in the system:
where, for the ADP3168, R' is the PCB resistance from the bulk capacitors to the ceramics and where R
ON resistance per phase. For this example, A
L
The compensation values can be solved using the following:
Choosing the closest standard values for the components yields
X
is 375 pH for the eight Al-Poly capacitors.
4
T
T
T
T
C
CA
C
C
C
R
R
R
B
C
D
A
E
E
A
B
FB
A
A
=
=
=
=
=
=
=
=
=
=
=
=
C
(
V
3
C
390
n
C
n
3
T
R
T
R
37
X
RT
T
×
R
C
X
B
×
X
×
A
B
×
R
D
A
1
×
E
1
9 .
×
+
×
R
R
=
=
pF
3 .
3 .
=
(
O
O
×
C
(
⎛
⎜
⎜
⎝
R
m
R
V
. 1
371
R
. 1
m
6
,
L
16
m
×
O
VID
X
×
R
'
Ω
−
O
2 .
33
521
R
97
Ω
B
Ω
−
×
T
−
R
7 .
A
A
−
×
µs
+
pF
A
×
O
k
D
C
×
µs
R
A
=
R
. 1
k
2
Ω
ns
5
)
D
R
'
Z
×
Ω
. 4
16
)
'
×
33
×
)
×
=
E
+
×
×
=
+
R
79
C
16
4
9 .
=
f
DS
k
. 1
R
R
C
L
R
2 .
SW
X
Ω
31
O
µs
7 .
DS
k
X
O
2
Z
48
+
=
Ω,
m
×
2 .
×
k
⎞
⎟
⎟
⎠
Ω
(
=
nF
R
1
Ω
R
C
pF
R
=
0 .
L
+
371
V
O
B
O
×
R
1
. 0
DID
m
=
=
6 .
−
X
V
63
Ω
pF
1
RT
R
. 6
m
5 .
+
'
V
1
56
Ω
=
0
+
nF
5 .
×
6 .
×
. 6
mF
D
1
2
V
,
⎛
⎜ ⎜
⎝
. 0
5 .
is 5, V
56
m
C
600
×
n
63
Ω
×
FB
. 6
V
L
mF
×
−
(
56
V
1
nH
×
=
×
C
1
3 .
RT
×
(
+
3 .
37
33
mF
X
1
m
equals 0.63 V, R' is approximately 0.6 mΩ (assuming a 4-layer motherboard), and
=
(
−
2
1
×
m
9 .
Ω
pF
3 .
(30)
(31)
(32)
(33)
n
×
3
2
×
Ω
5
R
−
m
×
×
×
600
O
m
230
)
×
Ω
0
Rev. B | Page 20 of 24
×
. 6
267
Ω
D
×
4
6 .
. 6
56
2 .
−
)
V
nH
µF
m
56
×
VID
0
m
kHz
Ω
mF
V
6 .
×
×
Ω
mF
RT
)
(
m
+
(
1
1
×
⎞
⎟ ⎟
⎠
Ω
3 .
230
−
1
=
=
3 .
)
. 0
m
. 1
Figure 13 shows the typical transient response using the
compensation values.
+
6
375
Ω
m
97
µF
2 .
375
1
)
Ω
3 .
2
µs
µs
×
)
×
m
×
1
pH
1
Ω
3 .
. 0
Figure 13. Typical Transient Response for Design Example
5 .
63
m
×
V
Ω
1
V
3 .
=
37
m
521
1
Ω
9 .
0 .
−
m
m
ns
0
Ω
Ω
6 .
m
Ω
DS
=
is the total low side MOSFET
. 4
79
µs
(25)
(26)
(27)
(28)
(29)