The LTC1555LEGN provides power conversion and level shifting needed for low voltage GSM cellular telephones to interface with either 3V or 5V Subscriber Identity Modules (SIMs). The part contains a patented buck/boost charge pump DC/DC converter* that delivers a regulated VCC supply voltage to the SIM card. Input voltage may range from 2.6V to 6V allowing direct connection to the battery. The output voltage may be programmed to 3V, 5V or direct connection to the VIN pin.
Internal level translators allow controllers operating with supplies as low as 1.425V to interface with 3V and 5V SIMs. A soft-start feature limits inrush current at turn-on, mitigating start-up problems that may result when the input is supplied by another low-power DC/DC converter. Battery life is maximized by 40µA operating current, and 1µA shutdown current. Board area is minimized by the miniature 16-pin narrow SSOP packages and the need for only three small external capacitors.
Feature
- Buck/Boost Charge Pump Generates 3V or 5V
- Input Voltage Range: 2.6V to 6V
- Controller VCC Range: 1.425V to 4.4V
- >10kV ESD on All SIM Contact Pins
- Short-Circuit and Overtemperature Protected
- 3V to 5V Signal Level Translators
- Very Low Operating Current: 40µA
- Very Low Shutdown Current: <1µA
- Soft-Start Limits Inrush Current at Turn-On
- 1MHz Switching Frequency
- Available in 16-Pin Narrow SSOP Package
Applications
- SIM Interface in GSM Cellular Telephones
- Smart Card Readers
(Picture: Pinout)
