MAX796 Datasheet, PDF (1/32 Pages) Maxim Integrated Products – Step-Down Controllers with Synchronous Rectifier for CPU Power

19-0221; Rev 3a; 11/97
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Step-Down Controllers with
Synchronous Rectifier for CPU Power
_______________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
SPECIAL FEATURE
3.3V/5V or adj.
Regulates positive secondary
voltage (such as +12V)
3.3V/5V or adj. Logic-controlled low-noise mode
3.3V/5V or adj.
Regulates negative secondary
voltage (such as -5V)
________________________Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Cellular Phones
____________________________Features
o 96% Efficiency
o 4.5V to 30V Input Range
o 2.5V to 6V Adjustable Output
o Preset 3.3V and 5V Outputs (at up to 10A)
o Multiple Regulated Outputs
o +5V Linear-Regulator Output
o Precision 2.505V Reference Output
o Automatic Bootstrap Circuit
o 150kHz/300kHz Fixed-Frequency PWM Operation
o Programmable Soft-Start
o 375µA Typ Quiescent Current (V_IN = 12V, V_OUT = 5V)
o 1µA Typ Shutdown Current
______________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
(SECFB) SKIP 2
REF 3
GND 4
SYNC 5
SHDN 6
FB 7
CSH 8
MAX796
MAX797
MAX799
16 ^DH
15 ^LX
14 ^BST
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.}
( ) ARE FOR MAX796/MAX799.
DIP/SO
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone] ext. 3468.