Rainbow Electronics MAX799 - Manual

_______________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.
________________________Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Cellular Phones
____________________________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
MAX796/MAX797/MAX799
Step-Down Controllers with
Synchronous Rectifier for CPU Power
________________________________________________________________ Maxim Integrated Products 1
PART
MAX799
MAIN OUTPUT SPECIAL FEATURE
3.3V/5V or adj.
Regulates negative secondary
voltage (such as -5V)
MAX797 3.3V/5V or adj. Logic-controlled low-noise mode
MAX796 3.3V/5V or adj.
Regulates positive secondary
voltage (such as +12V)
Idle Mode is a trademark of Maxim Integrated Products.
† U.S. and foreign patents pending.
19-0221; Rev 3a; 11/97
EVALUATION KIT MANUALS
FOLLOW DATA SHEET
__________________Pin Configuration
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
DH
LX
BST
DL GND
REF
(SECFB) SKIP
SS
TOP VIEW
MAX796
MAX797
MAX799
PGND
VL
V+
CSL
( ) ARE FOR MAX796/ MAX799.
CSH
FB
SHDN
SYNC
DIP/SO
Dice*
16 Narrow SO
16 Plastic DIP
PIN-PACKAGE TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C MAX796C/D
MAX796CSE
MAX796 CPE
PART †
16 CERDIP
16 Narrow SO
16 Plastic DIP -40°C to +85°C
-40°C to +85°C
-55°C to +125°C MAX796MJE
MAX796ESE
MAX796EPE
Ordering Information continued at end of data sheet.
*Contact factory for dice specifications.
______________Ordering Information
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.