MAX1844 High-Speed Step-Down Controller with Accurate Current Limit for Notebook Computers

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The MAX1844 pulse-width modulation (PWM) controller provides high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high-voltage batteries to generate low-voltage CPU core or chipset/RAM supplies in notebook computers.

Maxim's proprietary Quick-PWM™ quick-response, constant-on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns “instant-on” response to load transients while maintaining a relatively constant switching frequency. Efficiency is enhanced by an ability to drive very large synchronous-rectifier MOSFETs. Accurate current sensing to ensure reliable overload protection is available using an external current-sense resistor in series with the synchronous rectifier. Alternatively, the synchronous rectifier itself can be used for less accurate current sensing at the lowest possible power dissipation.

Single-stage buck conversion allows the MAX1844 to directly step down high-voltage batteries for the highest possible efficiency. Alternatively, two-stage conversion (stepping down the 5V system supply instead of the battery) at a higher switching frequency allows the minimum possible physical size.

The MAX1844 is intended for CPU core, chipset, DRAM, or other low-voltage supplies as low as 1V. It is available in 20-pin QSOP, and QFN packages and includes both adjustable overvoltage and undervoltage protection.

For a dual step-down PWM controller with accurate current limit, refer to the MAX1845. The MAX1714/ MAX1715 single/dual PWM controllers are similar to the MAX1844/MAX1845 but do not use current-sense resistors.

Key Features

Applications/Uses

Ultra-High Efficiency
Accurate Current-Limit Option
Quick-PWM with 100ns Load-Step Response
1% V_OUT Accuracy Over Line and Load
1.8V/2.5V Fixed or 1V to 5.5V Adjustable Output Range
2V to 28V Battery Input Range
200/300/450/600kHz Switching Frequency
Adjustable Overvoltage Protection
Adjustable Undervoltage Protection
1.7ms Digital Soft-Start
Drives Large Synchronous-Rectifier FETs
2V ±1% Reference Output
Power-Good Window Comparator

	1.8V and 2.5V Supplies
	Chipset/RAM Supplies as Low as 1V
	CPU Core Supplies
	Notebook Computers

Key Specifications: Step-Down Switching Regulators

Part Number

V_IN (min) (V)

V_IN (max) (V)

Min. V_OUT (V)

Max. V_OUT (V)

Preset V_OUT (V)

Output Adj. Method

Operating Current, I_CC (max) (mA)

Number of DC-DC Outputs

Operating Freq. (kHz)

Features

EV-Kit

Package

RoHS Available

Operating Temp. Range (°C)

Price^**

MAX1844

5.5

1.8
2.5

Preset
Resistor

0.8

300

•	Adjustable Frequency

•	Current Limit

•	Fixed Frequency/ PWM Operation

•	Output Overvoltage Protection

•	Output Undervoltage Protection

•

Shutdown

•	Soft Start

•	Synchronous Rectifier

Yes

QFN/20
QSOP/20
THIN QFN/20

Yes

-40 to +85

$2.60 @ 1k

See All Step-Down Switching Regulators (223)

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.