Datasheet
MAX8632
Transient Response (Buck)
The inductor ripple current also affects transient-
response performance, especially at low V
IN
- V
OUT
dif-
ferentials. Low inductor values allow the inductor
current to slew faster, replenishing charge removed
from the output filter capacitors by a sudden load step.
The output sag is also a function of the maximum duty
factor, which can be calculated from the on-time and
minimum off-time:
where t
OFF(MIN)
is the minimum off-time (see the
Electrical Characteristics) and K is from Table 1.
V
LI
VK
V
t
CV
VV K
V
t
SAG
LOAD MAX
OUT
IN
OFF MIN
OUT OUT
IN OUT
IN
OFF MIN
=
×
×
+
×
()
×
+
() ()
()
∆
2
2
-
Integrated DDR Power-Supply Solution for
Desktops, Notebooks, and Graphic Cards
24 ______________________________________________________________________________________
Figure 8. Typical Application Circuit
MAX8632
REF
ILIM
GND
PGND1
DL
VTTR
V
DD
FB
DH
LX
BST
V
IN
AV
DD
VTTI
VTT
POK1
V
IN
(4.5V TO 28V)
2.5V
/
12A
VTT
1.25V
/
±1.5A
5V
BIAS
SUPPLY
POK1
VTTR
1.25V
/
10mA
PGND2
REFIN
VTTS
OUT
TP0
POK2 POK2
SS
TON
OVP/UVP
Q1
IRF7821
n-CHANNEL
30V, 9mΩ
L1
TOKO FDA1254-1R0M
1.0µH, 21A, 1.6mΩ
D1
CMDSH-3
C11, C12 (150µF, 4V,
25mΩ, LOW-ESR POS
CAPACITOR (D2E)
SANYO 4TPE150M
Q2
IRF7832
n-CHANNEL
30V,5mΩ
C2
10µF
C4
20µF
C6
1µF
R3
100kΩ
R4
100kΩ
R5
47.5kΩ
R2
100kΩ
C9
3.9nF
C10
0.22µF
ON
OFF
C11
150µF
C12
150µF
C13
1µF
C7
0.22µF
C5
4.7µF
R1
10Ω
C3
1µF
C1
0.1µF
C14
470µF
(OPTIONAL)
SKIP
SHDN
STBY
C8
2 x 10µF
R6
20Ω