19-0221; Rev 4; 9/05
KIT
ATION
EVALU
BLE
AVAILA
Step-Down Controllers with
Synchronous Rectifier for CPU Power
The MAX796/MAX797/MAX799 high-performance, stepdown 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 secondary feedback input (SECFB) for transformer-based
dual-output applications. This secondary feedback path
improves cross-regulation of positive (MAX796) or negative (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 sensitive 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 16pin DIP and narrow SO packages. See the table below
to compare these three converters.
PART
MAIN OUTPUT
SPECIAL FEATURE
MAX796
3.3V/5V or adj
3.3V/5V or adj
Logic-controlled low-noise mode
MAX799
3.3V/5V or adj
Regulates negative secondary
voltage (such as -5V)
♦ 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 (VIN = 12V, VOUT = 5V)
1µA Typ Shutdown Current
_______________Ordering Information
PART†
TEMP RANGE
PIN-PACKAGE
MAX796CPE
0°C to +70°C
16 Plastic DIP
MAX796CSE
MAX796C/D
MAX796EPE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
16 Narrow SO
Dice*
16 Plastic DIP
MAX796ESE
MAX796MJE
-40°C to +85°C
-55°C to +125°C
16 Narrow SO
16 CERDIP
Ordering Information continued at end of data sheet.
*Contact factory for dice specifications.
Regulates positive secondary
voltage (such as +12V)
MAX797
____________________________Features
___________________Pin Configuration
TOP VIEW
SS 1
________________________Applications
16 DH
(SECFB) SKIP 2
15 LX
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
14 BST
REF 3
GND 4
Cellular Phones
SYNC 5
MAX796
MAX797
MAX799
13 DL
12 PGND
SHDN 6
11 VL
FB 7
10 V+
CSH 8
Idle Mode is a trademark of Maxim Integrated Products.
†U
9
CSL
DIP/SO
( ) ARE FOR MAX796/ MAX799.
________________________________________________________________ Maxim Integrated Products
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.
1
MAX796/MAX797/MAX799
_______________General Description
