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Step-Up DC-DC Converters with Precise, Adaptive Current Limit for GSM

Reduces GSM Battery Peak Current by 6x, Eliminates DC-DC Noise during Transmission with User Selectable Disable

Product Details

Key Features

Parametric specs for Step-Up Switching Regulators
VIN (V) (min) 2.7
VIN (V) (max) 6
VOUT1 (V) (min) 1.25
VOUT1 (V) (max) 6
IOUT1 (A) (max) 2.5
Switch Type Internal
Output Adjust. Method Resistor
Synchronous Switching? Yes
IQ (mA) (typ) 2
Shutdown Mode Supply Current (µA) (typ) 3
# DC-DC Outputs 1
Switching Frequency (kHz) 500
Package/Pins TSSOP/16
Budgetary
Price (See Notes)
3.34
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Simplified Block Diagram

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Parameters

Parametric specs for Step-Up Switching Regulators
VIN (V) (min) 2.7
VIN (V) (max) 6
VOUT1 (V) (min) 1.25
VOUT1 (V) (max) 6
IOUT1 (A) (max) 2.5
Switch Type Internal
Output Adjust. Method Resistor
Synchronous Switching? Yes
IQ (mA) (typ) 2
Shutdown Mode Supply Current (µA) (typ) 3
# DC-DC Outputs 1
Switching Frequency (kHz) 500
Package/Pins TSSOP/16
Budgetary
Price (See Notes)
3.34

Key Features

  • 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

Applications/Uses

  • GSM Phones
  • PC Cards (PCMCIA)
  • Wireless Handsets

Description

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.

Simplified Block Diagram

MAX1687, MAX1688: Typical Operating Circuit MAX1687, MAX1688: Typical Operating Circuit Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .

Sampling:
Selecting the Sample button above will redirect to the third-party ADI Sample Site. The part selected will carry over to your cart on this site once logged in. Please create a new account there if you have never used the site before. Contact SampleSupport@analog.com with any questions regarding this Sample Site.