19-1268; Rev 0; 8/97
IT
TION K
VALUA
E
BLE
AVAILA
Low-Voltage, Precision Step-Down
Controller for Portable CPU Power
____________________________Features
o
±1% DC Accuracy (Adjustable Mode)
o
Output Overvoltage Crowbar Protection
o
Output Undervoltage Shutdown
o
Adjustable Switching Frequency to 340kHz
o
Low-Dropout Operation
o
Idle Mode Pulse-Skipping Operation
o
1.10V to 5.5V Adjustable Output Voltage
o
2.5V/3.3V Dual-Mode Fixed-Output Settings
o
Internal Digital Soft-Start
o
1.1V ±1% Reference Output
o
3µA (typ) Shutdown Current
R
o
Open-Drain Power-Good Output (R
ESET
)
o
20-Pin SSOP Package
_______________General Description
The MAX1636 is a synchronous, buck, switch-mode,
power-supply controller that generates the CPU supply
voltage in battery-powered systems. It achieves ±1%
output voltage accuracy and offers the excellent load-
transient response needed by upcoming generations of
dynamic-clock CPUs.
Up to 95% efficiency is achieved through synchronous
rectification and Maxim’s proprietary Idle Mode™ con-
trol scheme. Efficiency is greater than 80% over a
1000:1 load-current range, extending battery life in sys-
tem-suspend or standby modes. Excellent dynamic
response corrects output load transients caused by the
latest dynamic-clock CPUs within five 300kHz clock
cycles. Strong, 1A, on-board gate drivers ensure fast,
external N-channel MOSFET switching.
The MAX1636 features a logic-controlled and synchro-
nizable, fixed-frequency, pulse-width-modulation (PWM)
operating mode that reduces noise and RF interference
in sensitive mobile communications and pen-entry appli-
cations. Holding
SKIP
high forces fixed-frequency mode
for lowest noise under all load conditions.
For a low-cost version that omits the +5V VL linear-
regulator block and comes in a smaller 16-pin QSOP
package, refer to the MAX1637 data sheet.
MAX1636
______________Ordering Information
PART
MAX1636EAP
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
20 SSOP
________________________Applications
Notebook Computers
Subnotebook Computers
Desktop Computers
Bus-Termination Supplies
V+
SHDN
__________Typical Operating Circuit
V
IN
__________________Pin Configuration
TOP VIEW
CSH 1
CSL 2
RESET 3
SHDN 4
OVP 5
CC 6
REF 7
SYNC 8
GND 9
GND 10
20 SKIP
19 LX
18 DH
17 BST
OVP
VL
V
CC
CC
DH
BST
LX
MAX1636
SKIP
SYNC
MAX1636
16 PGND
15 DL
14 VL
13 V+
12 V
CC
11 FB
DL
PGND
CSH
GND
CSL
FB
RESET
TO
µP
REF
GND
SSOP
Idle Mode is a trademark of Maxim Integrated Products.
________________________________________________________________
Maxim Integrated Products
1
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.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
