19-0221; Rev 4; 9/05
KIT
ATION
EVALU
BLE
AVAILA
Step-Down Controllers with
Synchronous Rectifier for CPU Power
____________________________Features
♦
96% Efficiency
♦
4.5V to 30V Input Range
♦
2.5V to 6V Adjustable Output
♦
Preset 3.3V and 5V Outputs (at up to 10A)
♦
Multiple Regulated Outputs
♦
+5V Linear-Regulator Output
♦
Precision 2.505V Reference Output
♦
Automatic Bootstrap Circuit
♦
150kHz/300kHz Fixed-Frequency PWM Operation
♦
Programmable Soft-Start
♦
375μA Typ Quiescent Current (V
IN
= 12V, V
OUT
= 5V)
♦
1μA Typ Shutdown Current
_______________General Description
The MAX796/MAX797/MAX799 high-performance, step-
down DC-DC converters with single or dual outputs
provide main CPU power in battery-powered systems.
These buck controllers achieve 96% efficiency by using
synchronous rectification and Maxim’s proprietary Idle
Mode™ control scheme to extend battery life at full-load
(up to 10A) and no-load outputs. Excellent dynamic
response corrects output transients caused by the latest
dynamic-clock CPUs within five 300kHz clock cycles.
Unique bootstrap circuitry drives inexpensive N-channel
MOSFETs, reducing system cost and eliminating the
crowbar switching currents found in some PMOS/NMOS
switch designs.
The MAX796/MAX799 are specially equipped with a sec-
ondary feedback input (SECFB) for transformer-based
dual-output applications. This secondary feedback path
improves cross-regulation of positive (MAX796) or nega-
tive (MAX799) auxiliary outputs.
The MAX797 has a logic-controlled and synchronizable
fixed-frequency pulse-width-modulating (PWM) operating
mode, which reduces noise and RF interference in sensi-
tive mobile-communications and pen-entry applications.
The SKIP override input allows automatic switchover to
idle-mode operation (for high-efficiency pulse skipping) at
light loads, or forces fixed-frequency mode for lowest noise
at all loads.
The MAX796/MAX797/MAX799 are all available in 16-
pin DIP and narrow SO packages. See the table below
to compare these three converters.
PART
MAX796
MAX797
MAX799
MAIN OUTPUT
3.3V/5V or adj
3.3V/5V or adj
3.3V/5V or adj
SPECIAL FEATURE
Regulates positive secondary
voltage (such as +12V)
Logic-controlled low-noise mode
Regulates negative secondary
voltage (such as -5V)
MAX796/MAX797/MAX799
_______________Ordering Information
PART
†
MAX796CPE
MAX796CSE
MAX796C/D
MAX796EPE
MAX796ESE
MAX796MJE
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
16 Plastic DIP
16 Narrow SO
Dice*
16 Plastic DIP
16 Narrow SO
16 CERDIP
Ordering Information continued at end of data sheet.
*Contact factory for dice specifications.
___________________Pin Configuration
TOP VIEW
SS 1
16 DH
15 LX
14 BST
________________________Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Cellular Phones
(SECFB) SKIP 2
REF 3
GND 4
SYNC 5
SHDN 6
FB 7
CSH 8
MAX796
MAX797
MAX799
13 DL
12 PGND
11 VL
10 V+
9
CSL
Idle Mode is a trademark of Maxim Integrated Products.
†
U.S. and foreign patents pending.
DIP/SO
( ) ARE FOR MAX796/ MAX799.
________________________________________________________________
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.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
