Hig h -Effic ie n c y, P WM, S t e p -Do w n
DC-DC Co n t ro lle rs in 1 6 -P in QS OP
S t a n d a rd Ap p lic a t io n Circ u it s
De t a ile d De s c rip t io n
It’s easy to adapt the basic MAX1653 single-output 3.3V
The MAX1652 family are BiCMOS, switch-mode power-
supply controllers designed primarily for buck-topology
regulators in battery-powered applications where high
efficiency and low quiescent supply current are critical.
The parts also work well in other topologies such as
boost, inverting, and Cuk due to the flexibility of their
floating high-speed gate driver. Light-load efficiency is
enhanced by automatic idle-mode operation—a vari-
a b le -fre q ue nc y p uls e -s kip p ing mod e tha t re d uc e s
losses due to MOSFET gate charge. The step-down
p owe r-s witc hing c irc uit c ons is ts of two N-c ha nne l
MOSFETs, a rectifier, and an LC output filter. The out-
put voltage is the average of the AC voltage at the
switching node, which is adjusted and regulated by
changing the duty cycle of the MOSFET switches. The
gate-drive signal to the N-channel high-side MOSFET
must exceed the battery voltage and is provided by a
flying capacitor boost circuit that uses a 100nF capaci-
tor connected to BST.
buck converter (Figure 1) to meet a wide range of appli-
cations with inputs up to 30V (limited by choice of exter-
na l MOSFET). Simp ly s ub s titute the a p p rop ria te
components from Table 1 (candidate suppliers are pro-
vided in Table 2). These circuits represent a good set of
trade-offs among cost, size, and efficiency while staying
within the worst-case specification limits for stress-relat-
ed parameters such as capacitor ripple current.
Don’t change the frequency of these circuits without
first recalculating component values (particularly induc-
tance value at maximum battery voltage).
For a d is c us s ion of d ua l-outp ut c irc uits us ing the
MAX1652 a nd MAX1654, s e e Fig ure 9 a nd the
Secondary Feedback-Regulation Loop section.
2–MAX165
INPUT
C1
C7
0.1µF
+5V AT
5mA
10
11
D2
CMPSH-3
C4
4.7µF
V+
VL
6
2
16
14
DH
Q1
ON/OFF
CONTROL
SHDN
BST
C3
0.1µF
+3.3V
OUTPUT
15
13
L1
LX
MAX1653
LOW-NOISE
CONTROL
SKIP
SS
R1
C2
DL
Q2
D1
GND
OUT
12
8
PGND
1
CSH
CSL
9
C6
0.01µF
(OPTIONAL)
4
3
GND
REF
FB
SYNC
C5
0.33µF
7
5
REF OUTPUT
NOTE: KEEP CURRENT-SENSE
LINES SHORT AND CLOSE
TOGETHER. SEE FIGURE 8.
+2.5V AT 100µA
J1
150kHz/300kHz
JUMPER
Figure 1. Standard 3.3V Application Circuit (see Table 1 for Component Values)
10 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
