MAX1687, MAX1688 升压型DC-DC转换器，带有精密的、自适应限流，用于GSM

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The MAX1687*/MAX1688* step-up DC-DC converters deliver up to 2W from a single Li-Ion or three NiMH cells. The devices are ideal for burst-load applications such as GSM cell phones and wireless LANs, where the RF power amplifiers require short, high current bursts. The MAX1687/MAX1688 reduce battery surge current by slowly charging a reservoir capacitor, which supplies the necessary peak energy for the load current burst. As a result, the peak battery current is limited, thus maximizing battery life and minimizing battery voltage sag and transient dips.

An internal synchronous rectifier provides over 90% conversion efficiency and eliminates the need for an external Schottky diode. A logic shutdown mode reduces the shutdown current to only 3µA. The devices can be disabled during current bursts (RF transmit mode) to eliminate switching noise.

The switching frequency of the MAX1687/MAX1688, controlled by the selected inductor, can exceed 1MHz. Two external resistors set the output voltage from 1.25V to 6V. The MAX1687 controls peak battery current, while the MAX1688 features a more advanced, adaptive constant-recharge-time algorithm that maximizes battery life. The MAX1687/MAX1688 are available in thin 16-pin TSSOP (1.1mm max height) or standard 8-pin SO packages.

关键特性

应用/使用

Low 450mA Peak Battery Current Provides 2A, 5V GSM Burst
90% Efficiency
Internal Power MOSFETs and Current-Sense Resistor
Output Disconnects from Input During Shutdown
3µA Shutdown Current
Precise Voltage-Controlled Current Limit (MAX1687)
Adaptive Constant-Recharge-Time Capability (MAX1688)
1.25V to 6V Adjustable Output
2.7V to 6V Input Range (1 Li-Ion cell or 3 NiMH cells)
Switching Frequency Can Exceed 1MHz
Standby Mode Disables DC-DC During Transmission Burst
Low Inrush Current at Start-Up

	GSM电话
	PC卡(PCMCIA)
	无线手机

Key Specifications: Step-Up Switching Regulators

Part Number

V_IN (min) (V)

V_IN (max) (V)

Min. V_OUT (V)

Max. V_OUT (V)

I_OUT (A)

Output Adj. Method

Operating Current, I_CC (max) (mA)

Number of DC-DC Outputs

Fixed Freq/PWM Operation

Operating Freq. (kHz)

Internal Power Switch(es)

Synchronous Rectifier

Features

EV-Kit

Package

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

RoHS Available

Operating Temp. Range (°C)

Price^**

MAX1687

2.7

1.25

2.5

Resistor

Yes

500

Yes

•	Adjustable Frequency

•	Current limit

•

Shutdown

•	Soft Start

Yes

SOIC/8
TSSOP/16

Yes

-40 to +85

$2.20 @ 1k

MAX1688

$2.20 @ 1k

See All Step-Up Switching Regulators (89)

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

Package

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

Price^**

MAX1687

Step-Up

2.7

1.25

2.5

Yes

500

Yes

SOIC/8
TSSOP/16

$2.20 @ 1k

MAX1688

$2.20 @ 1k

See All Switch-Mode DC-DC Power Supplies (429)

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.