19-3501; Rev 0; 11/04
High-Efficiency, 5x Output, Main Power-Supply
Controllers for Notebook Computers
General Description
Features
The MAX1533/MAX1537 are dual step-down, switch-
mode power-supply (SMPS) controllers with synchro-
nous rectification, intended for main 5V/3.3V power
generation in battery-powered systems. Fixed-frequen-
cy operation with optimal interleaving minimizes input
ripple current from the lowest input voltages up to the
26V maximum input. Optimal 40/60 interleaving allows
the input voltage to go down to 8.3V before duty-cycle
overlap occurs, compared to 180° out-of-phase regula-
tors where the duty-cycle overlap occurs when the
input drops below 10V. Output current sensing pro-
vides accurate current limit using a sense resistor.
Alternatively, power dissipation can be reduced using
lossless inductor current sensing.
♦ Fixed-Frequency, Current-Mode Control
♦ 40/60 Optimal Interleaving
♦ Accurate Differential Current-Sense Inputs
♦ Internal 5V and 3.3V Linear Regulators with
100mA Load Capability
♦ Auxiliary 12V or Adjustable 150mA Linear
Regulator (MAX1537 Only)
♦ Dual-Mode™ Feedback—3.3V/5V Fixed or
Adjustable Output (Dual Mode) Voltages
♦ 200kHz/300kHz/500kHz Switching Frequency
♦ Versatile Power-Up Sequencing
Internal 5V and 3.3V linear regulators power the
MAX1533/MAX1537 and their gate drivers, as well as
external keep-alive loads, up to a total of 100mA. When
the main PWM regulators are in regulation, automatic
bootstrap switches bypass the internal linear regulators,
providing currents up to 200mA from each linear output.
An additional 5V to 23V adjustable internal 150mA linear
regulator is typically used with a secondary winding to
provide a 12V supply.
♦ Adjustable Overvoltage and Undervoltage
Protection
♦ 6V to 26V Input Range
♦ 2V 0.75ꢀ Reference Output
♦ Power-Good Output
♦ Soft-Shutdown
The MAX1533/MAX1537 include on-board power-up
sequencing, a power-good (PGOOD) output, digital
soft-start, and internal soft-shutdown output discharge
that prevents negative voltages on shutdown. The
MAX1533 is available in a 32-pin 5mm x 5mm thin QFN
package, and the MAX1537 is available in a 36-pin
6mm x 6mm thin QFN package. The exposed backside
pad improves thermal characteristics for demanding
linear keep-alive applications.
♦ 5µA (typ) Shutdown Current
Pin Configurations
TOP VIEW
32
31
30
29
28
27
26
25
ON5
ON3
1
2
3
4
5
6
7
8
24 FB5
Applications
23
22
LDO5
DL5
2 to 4 Li+ Cells Battery-Powered Devices
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
FSEL
ILIM3
ILIM5
REF
21 PGND
MAX1533
20
19
DL3
Ordering Information
LDO3
GND
18 FB3
17
PART
TEMP RANGE PIN-PACKAGE
V
CSL3
MAX1533ETJ
MAX1533ETJ+
MAX1537ETX
-40°C to +85°C 32 Thin QFN 5mm x 5mm
-40°C to +85°C 32 Thin QFN 5mm x 5mm
-40°C to +85°C 36 Thin QFN 6mm x 6mm
CC
9
10 11 12 13 14 15 16
MAX1537ETX+ -40°C to +85°C 36 Thin QFN 6mm x 6mm
+Denotes lead-free package.
THIN QFN
5mm x 5mm
Pin Configurations continued at end of data sheet.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.