Rainbow Electronics MAX1635 - Manual

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________________General Description
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 SKIP 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.
________________________Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Desktop CPU Local DC-DC Converters
____________________________Features
♦ 96% Efficiency
♦ +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
(MAX1631/MAX1634)
♦ 5V/50mA Linear Regulator Output
♦ Precision 2.5V Reference Output
♦ Programmable Power-Up Sequencing
♦ Power-Good (RESET) Output
♦ Output Overvoltage Protection
(MAX1630/MAX1631/MAX1632)
♦ Output Undervoltage Shutdown
(MAX1630/MAX1631/MAX1632)
♦ 200kHz/300kHz Low-Noise, Fixed-Frequency
Operation
♦ Low-Dropout, 99% Duty-Factor Operation
♦ 2.5mW Typical Quiescent Power (+12V input, both
SMPSs on)
♦ 4µA Typical Shutdown Current
♦ 28-Pin SSOP Package
MAX1630–MAX1635
Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
________________________________________________________________ Maxim Integrated Products 1
5V
LINEAR
12V
LINEAR
POWER-UP
SEQUENCE POWER-
GOOD
3.3V
SMPS
5V
SMPS
RESET ON/OFF
+5V (RTC)
+3.3V
INPUT
+5V
+12V
________________Functional Diagram
19-0480; Rev 3; 4/97
PART
MAX1630 CAI
MAX1630EAI -40°C to +85°C
0°C to +70°C
TEMP. RANGE PIN-PACKAGE
28 SSOP
28 SSOP
EVALUATION KIT
AVAILABLE
_______________Ordering Information
Ordering Information continued on last page.
Pin Configurations and Selector Guide appear at end of data
sheet.
Idle Mode and Dual Mode are trademarks of Maxim Integrated
Products.