MAX8734 Maxim Integrated Products, MAX8734 Datasheet - Page 16

• Manufacturer Part Number: MAX8734
• Description: (MAX8732 - MAX8734) Main Power-Supply Controllers
• Manufacturer: Maxim Integrated Products

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High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
MAX8733 is optimized for “thin and light” applications with a
5V/400kHz SMPS and a 3.3V/500kHz SMPS. The MAX8734
provides a pin-selectable switching frequency, allowing
either 200kHz/300kHz or 400kHz/500kHz operation of the
5V/3.3V SMPSs, respectively.
Light-load efficiency is enhanced by automatic Idle-
Mode operation, a variable-frequency pulse-skipping
mode that reduces transition and gate-charge losses.
Figure 3. Detailed Functional Diagram
16
______________________________________________________________________________________
(MAX8734 ONLY)
(MAX8732/
TON
MAX8733)
CS3
BST3
SHDN
ILIM3
OUT3
LDO3
DH3
LX3
ON3
ON5
PRO
DL3
FB3
LDO5
MAX8732
MAX8733
MAX8734
POWER-ON SEQUENCE/
CLEAR FAULT LATCH
LINEAR
REG
3V
EN3
CONTROLLER
SMPS PWM
3.3V
2.91V
GND
V+
Each 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 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 capacitor connected
to BST_.
SHUTDOWN
THERMAL
4.56V
CONTROLLER
PGOOD3
SMPS PWM
5V
PGOOD5
LINEAR
EN5
REG
5V
REFERENCE
2V
LDO5
BST5
DH5
LX5
V
PGOOD
DL5
(MAX8732/
ILIM5
FB5
OUT5
LDO5
REF
MAX8733)
CC
CS5