MAX1715 Maxim, MAX1715 Datasheet - Page 10

• Manufacturer Part Number: MAX1715
• Description: Ultra-High Efficiency / Dual Step-Down Controller for Notebook Computers
• Manufacturer: Maxim

Ultra-High Efficiency, Dual Step-Down
Controller for Notebook Computers
10
The standard application circuit (Figure 1) generates
two low-voltage rails for general-purpose use in note-
book computers (I/O supply, fixed CPU core supply,
DRAM supply). This DC-DC converter steps down a
battery or AC adapter voltage to voltages from 1.0V to
5.5V with high efficiency and accuracy.
See Table 1 for a list of components for common appli-
cations. Table 2 lists component manufacturers.
The MAX1715 buck controller is designed for low-volt-
age power supplies for notebook computers. Maxim’s
proprietary Quick-PWM pulse-width modulator in the
MAX1715 (Figure 2) is specifically designed for han-
dling fast load steps while maintaining a relatively con-
stant operating frequency and inductor operating point
Figure 1. Standard Application Circuit
______________________________________________________________________________________
V
BIAS SUPPLY
PINS 15, 23, 28 = N.C.
DD
4.7µF
C9
= 5V
Standard Application Circuit
1µF
C8
C11
1µF
Detailed Description
C3
OUTPUT1
1.8V
R1
20Ω
L1
C1
D1
0.22µF
N1
N2
C7
0.1µF
C5
12
20
21
25
26
27
24
3
5
1
9
2
8
V
V
ILIM1
ILIM2
ON1
BST1
DH1
LX1
DL1
TON
OUT1
REF
FB1
AGND
DD
CC
over a wide range of input voltages. The Quick-PWM
architecture circumvents the poor load-transient timing
problems of fixed-frequency current-mode PWMs while
also avoiding the problems caused by widely varying
switching frequencies in conventional constant-on-time
and constant-off-time PWM schemes.
The MAX1715 requires an external +5V bias supply in
addition to the battery. Typically, this +5V bias supply
is the notebook’s 95% efficient +5V system supply.
Keeping the bias supply external to the IC improves
efficiency and eliminates the cost associated with the
+5V linear regulator that would otherwise be needed to
supply the PWM circuit and gate drivers. If stand-alone
capability is needed, the +5V supply can be generated
with an external linear regulator such as the MAX1615.
MAX1715
V+
4
PGOOD
D3
CMPSH-3A
PGND
OUT2
BST2
SKIP
ON1
ON2
DH2
LX2
DL2
FB2
10
11
18
17
16
19
22
14
6
13
7
+5V Bias Supply (V
C6
0.1µF
+5V
100k
N3
N4
D2
V
4.5V TO 28V
C2
IN
L2
POWER-GOOD
INDICATOR
ON/OFF
CONTROLS
CC
OUTPUT2
C4
2.5V
and V
DD
)