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MAX797

Step-Down Controllers with Synchronous Rectifier for CPU Power

We Recommend Improved Performance Devices: MAX1652/MAX1653/MAX1654/MAX1655 for New Designs

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Overview

Description

The MAX796/MAX797/MAX799 high-performance, step-down DC-DC converters with single or dual outputs provide main CPU power in battery-powered systems. These buck controllers achieve 96% efficiency by using synchronous rectification and Maxim's proprietary Idle Mode™ control scheme to extend battery life at full-load (up to 10A) and no-load outputs. Excellent dynamic response corrects output transients caused by the latest dynamic-clock CPUs within five 300kHz clock cycles. Unique bootstrap circuitry drives inexpensive N-channel MOSFETs, reducing system cost and eliminating the crowbar switching currents found in some PMOS/NMOS switch designs.

The MAX796/MAX799 are specially equipped with a secondary feedback input (SECFB) for transformer-based dual-output applications. This secondary feedback path improves cross-regulation of positive (MAX796) or negative (MAX799) auxiliary outputs.

The MAX797 has a logic-controlled and synchronizable fixed-frequency pulse-width-modulating (PWM) operating mode, which reduces noise and RF interference in sensitive mobile-communications and pen-entry applications. The SKIP-bar override input allows automatic switchover to idle-mode operation (for high-efficiency pulse skipping) at light loads, or forces fixed-frequency mode for lowest noise at all loads.

The MAX796/MAX797/MAX799 are all available in 16-pin DIP and narrow SO packages. See the table below to compare these three converters.

MAX796, MAX797, MAX799: Typical Operating Circuits

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Key Features

96% Efficiency
4.5V to 30V Input Range
2.5V to 6V Adjustable Output
Preset 3.3V and 5V Outputs (at up to 10A)
Multiple Regulated Outputs
+5V Linear-Regulator Output
Precision 2.505V Reference Output
Automatic Bootstrap Circuit
150kHz/300kHz Fixed-Frequency PWM Operation
Programmable Soft-Start
375µA Typ Quiescent Current (V_IN = 12V, V_OUT = 5V)
1µA Typ Shutdown Current

Applications/Uses

Cell Phones
Notebook and Subnotebook Computers
PDAs and Mobile Communicators

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

MAX797

4.5

2.5

External

Yes

340

Adjustable Freq.

Current Limit

External Sync.

Fixed Freq./PWM

$5.85 @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

MAX797EVKIT: Evaluation Kit for the MAX797

Technical Documents

App Note 930 Synchronous Buck-Regulator Output Terminates High-Speed Data Buses
App Note 851 Battery Charger Delivers 2.5A with > 96% Efficiency

Quality And Environmental

Product Reliability Reports: MAX797.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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