Lo w -Vo lt a g e , P re c is io n S t e p -Do w n
Co n t ro lle r fo r P o rt a b le CP U P o w e r
Table 2. Component Suppliers
POWER INPUT
FACTORY FAX
COMPANY
AVX
USA PHONE
(803) 946-0690
(516) 435-1110
0.1µF
(COUNTRY CODE)
(1) 803-626-3123
SHDN
OVP
SYNC
VL
V+
Central
Semiconductor
(1) 516-435-1824
4.7µF
Coilcraft
Coiltronics
Dale
(1) 847-639-1469
(1) 561-241-9339
(1) 605-665-1627
(1) 408-721-1635
(847) 639-6400
(561) 241-7876
(605) 668-4131
(408) 721-2181
V
C1
CC
MAX136
1nF
MAX1636
CMPSH-3
CC
BST
DH
Q1
Fairchild
REF
0.1µF
L1
R1
OUTPUT
International
Rectifier (IR)
1µF
(1) 310-322-3332
(1) 512-992-3377
(310) 322-3331
(512) 992-7900
LX
DL
GND
C2
Q2
*
IRC
GND
PGND
Marcon/United
Chemi-Con
IRC
(1) 847-696-9278
(1) 512-992-3377
(847) 696-2000
(512) 992-7900
CSH
CSL
Matsuo
Motorola
Panasonic
Sanyo
(1) 714-960-6492
(1) 602-994-6430
(1) 714-373-7183
(81) 7-2070-1174
(1) 408-970-3950
(1) 603-224-1430
(81) 3-3607-5144
(1) 847-390-4428
(1) 408-434-0375
(714) 969-2491
(602) 303-5454
(714) 373-7939
(619) 661-6835
(408) 988-8000
(603) 224-1961
(847) 956-0666
(847) 390-4373
(408) 432-8020
V
CC
R2
R3
10k
RESET
FB
Siliconix
Sprague
Sumida
TDK
SKIP
*SEE RECTIFIER CLAMP DIODE SECTION
Tokin
Figure 1. Standard Application Circuit
The pulse-width-modulation (PWM) controller consists
of a Dual Mode™ feedback network and multiplexer, a
multi-input PWM comparator, high-side and low-side
gate drivers, and logic. The MAX1636 contains fault-
protection circuits that monitor the PWM output for
undervoltage and overvoltage. Bias generator blocks
include the 5V (VL) linear regulator and the 1.1V preci-
sion reference. The PWM uses a 200kHz/300kHz syn-
chronizable oscillator. The circuit blocks are powered
from an internal IC power rail that receives power from
_______________De t a ile d De s c rip t io n
The MAX1636 is a BiCMOS, switch-mode, power-sup-
ply controller designed primarily for buck-topology reg-
ulators in battery-powered applications where high
efficiency and low quiescent supply current are critical.
Light-load efficiency is enhanced by automatic Idle
Mode operation, a variable-frequency, pulse-skipping
mode that reduces transition and gate-charge losses.
The step-down, power-switching circuit consists of two
N-channel MOSFETs, a rectifier, and an LC output filter.
The output voltage is the average AC voltage at the
switching node, which is regulated by changing the
duty cycle of the MOSFET switches. The gate-drive sig-
nal to the N-channel high-side MOSFET, which must
exceed the battery voltage, is provided by a flying-
capacitor boost circuit that uses a 100nF capacitor
between BST and LX. The MAX1636 contains 10 major
circuit blocks (Figure 2).
either VL or V . The synchronous-switch gate driver is
CC
powered directly from VL, while the high-side-switch
gate driver is powered indirectly from VL via an external
diode-capacitor boost circuit.
Dual Mode is a trademark of Maxim Integrated Products.
10 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
