QuickView - MAX8744A, MAX8745A High-Efficiency, Quad Output, Main Power-Supply Controllers for Notebook Computers

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Description

FULL DATA SHEET (PDF, 600kB)
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The MAX8744A/MAX8745A are dual step-down, switch-mode, power-supply (SMPS) controllers with synchronous rectification, intended for main 5V/3.3V power generation in battery-powered systems. Fixed-frequency operation with optimal interleaving minimizes input ripple current from the lowest input voltages up to the 26V maximum input. Optimal 40/60 interleaving allows the input voltage to go down to 8.3V before duty-cycle overlap occurs, compared to 180° out-of-phase regulators where the duty-cycle overlap occurs when the input drops below 10V.

Output current sensing provides peak current-limit protection, using either an accurate sense resistor or using lossless inductor DCR current sensing. A low-noise mode maintains high light-load efficiency while keeping the switching frequency out of the audible range.

An internal, fixed 5V, 100mA linear regulator powers up the MAX8744A/MAX8745A and their gate drivers, as well as external keep-alive loads. When the main PWM regulator is in regulation, an automatic bootstrap switch bypasses the internal linear regulator, providing current up to 200mA. An additional adjustable linear-regulator driver with an external pnp transistor can be used with a secondary winding to provide a 12V supply, or powered directly from the main outputs to generate low-voltage outputs as low as 1V.

Independent enable controls and power-good signals allow flexible power sequencing. Voltage soft-start gradually ramps up the output voltage and reduces inrush current, while soft-shutdown gradually ramps the output voltage down, preventing negative voltage dips. The MAX8744A/MAX8745A feature output undervoltage and thermal-fault protection. The MAX8744A also includes output overvoltage-fault protection.

The MAX8744A/MAX8745A are available in a 32-pin, 5mm x 5mm, thin QFN package. The exposed backside pad improves thermal characteristics for demanding linear keep-alive applications.

Key Features

Applications/Uses

Fixed-Frequency, Current-Mode Control
40/60 Optimal Interleaving
Internal BST Switches
Internal 5V, 100mA Linear Regulator
Auxiliary Linear-Regulator Driver (12V or Adjustable Down to 1V)
Dual Mode™ Feedback—3.3V/5V Fixed or Adjustable Output Voltages
200kHz/300kHz/500kHz Switching Frequency
Undervoltage and Thermal-Fault Protection
Overvoltage-Fault Protection (MAX8744A Only)
6V to 26V Input Range
2V ±0.75% Reference Output
Independent Enable Inputs and Power-Good Outputs
Soft-Start and Soft-Shutdown (Voltage Ramp)
8µA (typ) Shutdown Current

	2 to 4 Li+ Cell Battery-Powered Devices
	Main Power Supplies
	Notebook and Subnotebook Computers
	PDAs and Mobile Communicators

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)

I_OUT (A)

Output Adj. Method

Operating Current, I_CC (max) (mA)

Number of DC-DC Outputs

Operating Freq. (kHz)

Package

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

Price^**

MAX8744A

5.5

3.3
5.0

Preset
Resistor

0.036

500

TQFN/32

$4.55 @ 1k

MAX8745A

See Data Sheet

See All Step-Down Switching Regulators (252)

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.