MAX1636 Datasheet, PDF (10/24 Pages) Maxim Integrated Products – Low-Voltage, Precision Step-Down Controller for Portable CPU Power

Low-Voltage, Precision Step-Down
Controller for Portable CPU Power
POWER INPUT
0.1µF
SHDN V+ OVP
SYNC
VL
V_CC
1nF
CC ^MAX1636 BST
DH
REF
1µF
GND
LX
DL
GND
PGND
CSH
V_CC
CSL
10k
RESET
FB
SKIP
4.7µF
C1
CMPSH-3
Q1
0.1µF
L1
Q2 *
*SEE RECTIFIER CLAMP DIODE SECTION
Figure 1. Standard Application Circuit
R1 OUTPUT
C2
R2
R3
Table 2. Component Suppliers
COMPANY
AVX
Central
Semiconductor
Coilcraft
Coiltronics
Dale
Fairchild
International
Rectifier (IR)
IRC
Marcon/United
ICRhCemi-Con
Matsuo
Motorola
Panasonic
Sanyo
Siliconix
Sprague
Sumida
TDK
Tokin
FACTORY FAX
(COUNTRY CODE)
(1) 803-626-3123
(1) 516-435-1824
(1) 847-639-1469
(1) 561-241-9339
(1) 605-665-1627
(1) 408-721-1635
(1) 310-322-3332
(1) 512-992-3377
(1) 847-696-9278
(1) 512-992-3377
(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
USA PHONE
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[phone]
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[phone]
[phone]
[phone]
[phone]
[phone]
[phone]
[phone]
[phone]
[phone]
_______________Detailed Description
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).
Dual Mode is a trademark of Maxim Integrated Products.
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
either VL or V_CC. The synchronous-switch gate driver is
powered directly from VL, while the high-side-switch
gate driver is powered indirectly from VL via an external
diode-capacitor boost circuit.
10 ______________________________________________________________________________________