MAX1901, MAX1902, MAX1904 500kHz Multi-Output, Low-Noise Power-Supply Controllers for Notebook Computers

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The MAX1901/MAX1902/MAX1904 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 networks, and automatic bootstrapping.

Up to 97% 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 within five clock cycles. Strong 1A on-board gate drivers ensure fast external N-channel MOSFET switching.

These devices feature a logic-controlled and synchronizable, fixed-frequency, pulse-width modulation (PWM) operating mode. This reduces noise and RF interference in sensitive mobile communications and pen-entry applications. Asserting the active-low SKIP pin enables fixed-frequency mode, for lowest noise under all load conditions.

The MAX1901/MAX1902/MAX1904 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 MAX1902 contains a 12V/120mA linear regulator. The MAX1901/MAX1904 include a secondary feedback input (SECFB), plus a control pin (STEER) that selects which PWM (3.3V or 5V) receives the secondary feedback signal. SECFB provides a method for adjusting the secondary winding voltage regulation point with an external resistor divider, and is intended to aid in creating auxiliary voltages other than fixed 12V.

The MAX1901/MAX1902 contain internal output overvoltage and undervoltage protection features.

Key Features

Applications/Uses

	97% 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 (MAX1901/MAX1904)
	5V/50mA Linear Regulator Output
	Precision 2.5V Reference Output
	Programmable Power-Up Sequencing
	Power-Good (active-low RESET) Output
	Output Overvoltage Protection (MAX1901/MAX1902)
	Output Undervoltage Shutdown (MAX1901/MAX1902)
	333kHz/500kHz Low-Noise, Fixed-Frequency Operation
	Low-Dropout, 98% Duty-Factor Operation
	2.5mW Typical Quiescent Power (12V input, both SMPSs on)
	4µA Typical Shutdown Current

	Desktop CPU Local DC-DC Converters
	Notebook and Subnotebook Computers
	PDAs and Mobile Communicators

Key Specifications: Switch-Mode DC-DC Power Supplies

Part Number

Topology

V_IN (min) (V)

V_IN (max) (V)

Number of DC-DC Outputs

Digital/VID Programmed Output

Min. Adjustable V_OUT (V)

Max. Adjustable V_OUT (V)

I_OUT (A)

Operating Current, I_CC (max) (mA)

Fixed Freq/PWM Operation

Operating Freq. (kHz)

Internal Power Switch(es)

Synchronous Rectifier

Industry Qualified

Package

Smallest Available Package (max w/pins) (mm²)

Price^**

MAX1901

Step-Down

4.2

2.5

5.5

0.05

Yes

330

Yes

SSOP/28
THIN QFN/32

$5.55 @ 1k

MAX1902

SSOP/28

$5.55 @ 1k

MAX1904

Automotive - AECQ100
Automotive - General

SSOP/28
THIN QFN/32

$5.55 @ 1k

See All Switch-Mode DC-DC Power Supplies (421)

Notes:
^**This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the price and availability page or contact an authorized distributor.