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MAX1843

2.7A, 1MHz, Low-Voltage, Step-Down Regulator with Internal Synchronous Rectification in TQFN Package

2.7A, 1MHz, Internal Switch Step Down Regulator

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Overview

Description

The MAX1843 constant-off-time, pulse-width modulated (PWM) step-down DC-DC converter is ideal for use in 5V and 3.3V to low-voltage conversion necessary in notebook and subnotebook computers. This device features an internal PMOS power switch and internal synchronous rectification for high efficiency and reduced component count. An external Schottky diode is not required. The internal 90mΩ power switch and 70mΩ nMOS synchronous-rectifier switch easily deliver continuous load currents up to 2.7A. The MAX1843 produces a preset +2.5V, +1.8V, or +1.5V output voltage or an adjustable output from +1.1V to V_IN. It achieves efficiencies as high as 95%.

The MAX1843 uses a unique current-mode, constant-off-time, PWM control scheme, which includes Idle Mode™ to maintain high efficiency during light-load operation. The programmable constant-off-time architecture sets switching frequencies up to 1MHz, allowing the user to optimize performance trade-offs between efficiency, output switching noise, component size, and cost. The MAX1843 features an adjustable soft-start to limit surge currents during startup, a 100% duty-cycle mode for low dropout operation, and a low-power shutdown mode that disconnects the input from the output and reduces supply current below 1µA. The MAX1843 is available in a 28-pin TQFN package with an exposed backside pad.

MAX1843: Typical Operating Circuit

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Key Features

±1% Output Accuracy
Up to 1MHz Switching Frequency
95% Efficiency
Internal pMOS/nMOS Switches

90mΩ/70mΩ On-Resistance at V_IN = +4.5V
110mΩ/80mΩ On-Resistance at V_IN = +3V

Output Voltage

+2.5V, +1.8V, or +1.5V Pin Selectable
+1.1V to V_IN Adjustable

+3V to +5.5V Input Voltage Range
350µA Operating Supply Current
< 1µA Shutdown Supply Current
Programmable Constant-Off-Time Operation
Idle Mode Operation at Light Loads
Thermal Shutdown
Adjustable Soft-Start Inrush Current Limiting
100% Duty Cycle During Low-Dropout Operation
Output Short-Circuit Protection
28-Pin TQFN Package

Applications/Uses

5V or 3.3V to Low-Voltage Conversion
Chipset Supplies
CPU I/O Ring
Notebook and Subnotebook Computers

Parametric Specs

See parametric specs for Step-Down Switching Regulators (404)

Part Number

V_IN
(V)

V_OUT1
(V)

I_OUT1
(A)

Switch Type

Synchronous Switching

Oper. Freq.
(kHz)

Features

Package/Pins

Budgetary
Price

min

max

min

max

See Notes

MAX1843

5.5

1.1

5.5

2.7

Internal

Yes

1000

Adjustable Freq.

Current Limit

Fixed Freq./PWM

QFN/28

TQFN/28

$4.66 @1k

Pricing 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 and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Design Resources

Quality And Environmental

Product Reliability Reports: MAX1843.pdf

Device	Fab Process	Technology	Sample size	Rejects	FIT at 25°C	FIT at 55°C	Material Composition

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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