19-0480; Rev 3; 4/97
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
+4.2V to +30V Input Range
2.5V to 5.5V Dual Adjustable Outputs
Selectable 3.3V and 5V Fixed or Adjustable
Outputs (Dual Mode™)
12V Linear Regulator
Adjustable Secondary Feedback
5V/50mA Linear Regulator Output
Precision 2.5V Reference Output
Programmable Power-Up Sequencing
Power-Good (RESET) Output
Output Overvoltage Protection
Output Undervoltage Shutdown
200kHz/300kHz Low-Noise, Fixed-Frequency
Low-Dropout, 99% Duty-Factor Operation
2.5mW Typical Quiescent Power (+12V input, both
4µA Typical Shutdown Current
28-Pin SSOP Package
The MAX1630–MAX1635 are buck-topology, step-down,
switch-mode, power-supply controllers that generate
logic-supply voltages in battery-powered systems. These
high-performance, dual/triple-output devices include on-
board power-up sequencing, power-good signaling with
delay, digital soft-start, secondary winding control, low-
dropout circuitry, internal frequency-compensation net-
works, and automatic bootstrapping.
Up to 96% efficiency is achieved through synchronous
rectification and Maxim’s proprietary Idle Mode™ control
scheme. Efficiency is greater than 80% over a 1000:1
load-current range, which extends battery life in system-
suspend or standby mode. 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.
These devices feature a logic-controlled and synchroniz-
able, fixed-frequency, pulse-width-modulation (PWM)
operating mode. This reduces noise and RF interference
in sensitive mobile communications and pen-entry appli-
cations. Asserting the
pin enables fixed-frequency
mode, for lowest noise under all load conditions.
The MAX1630–MAX1635 include two PWM regulators,
adjustable from 2.5V to 5.5V with fixed 5.0V and 3.3V
modes. All these devices include secondary feedback
regulation, and the MAX1630/MAX1632/MAX1633/
MAX1635 each contain 12V/120mA linear regulators. The
MAX1631/MAX1634 include a secondary feedback input
(SECFB), plus a control pin (STEER) that selects which
PWM (3.3V or 5V) receives the secondary feedback sig-
nal. SECFB provides a method for adjusting the sec-
ondary winding voltage regulation point with an external
resistor divider, and is intended to aid in creating auxiliary
voltages other than fixed 12V.
The MAX1630/MAX1631/MAX1632 contain internal out-
put overvoltage and undervoltage protection features.
0°C to +70°C
-40°C to +85°C
Ordering Information continued on last page.
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Desktop CPU Local DC-DC Converters
Pin Configurations and Selector Guide appear at end of data
Idle Mode and Dual Mode are trademarks of Maxim Integrated
Maxim Integrated Products
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.