Features: Step-Up/Step-Down Charge Pump Generates 5V
Input Voltage Range: 2.7V to 10V
Output Current: 10mA (V IN 2.7V)
20mA (V IN 3V)
3V to 5V Signal Level Translators
>10kV ESD on All SIM Contact Pins
Short-Circuit and Overtemperature Protected
Very Low Operating Current: 60A
Very Low Shutdown Current: <1A
Soft Start Limits Inrush Current at Turn-On
Programmable 3V or 5V Output Voltage
650kHz Switching Frequency
Auxiliary 4.3V LDO/Power Switch (LTC1556 Only)
Available in a 16- and 20-Pin Narrow SSOPApplicationSIM Interface in GSM Cellular Telephones
Smart Card Readers
SpecificationsVIN , DVcc to GND ...................................... 0.3V to 12V
Vcc to GND.................................................. 0.3V to 12V
Digital Inputs to GND................................... 0.3V to 12V
LDO, CLK, RST, I/O to GND.............. 0.3V to (V cc+ 0.3V)
Vcc , LDO Short-Circuit Duration........................ Indefinite
Storage Temperature Range............... 65°C to 150°C
Temperature Range
LTC1555C/LTC1556C..................................0°C to 70°C
LTC1555I/LTC1556I ........................... ..40°C to 85°C
Extended Commercial Operating Temperature Range
(Note 2)............................................. .. 40°C to 85°C
Lead Temperature (Soldering, 10 sec)..................300°C
Description
The LTC(R) 1555/LTC1556 provide power conversion and level shifting needed for 3V GSM cellular telephones to interface with either 3V or 5V Subscriber Identity Mod- ules (SIMs). These parts contain a charge pump DC/DC converter that delivers a regulated 5V to the SIM card. Input voltage may range from 2.7V to 10V, allowing direct connection to the battery. Output voltage may be programmed to 3V, 5V or direct connection to the VIN pin.
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. The LTC1556 also includes an auxiliary LDO regulator/ power switch that may be used to power the frequency synthesizer or other low power circuitry.
Battery life is maximized by 60A operating current and 1A shutdown current. Board area is minimized by minia- ture 16- and 20-pin narrow SSOP packages and the need for only three small external capacitors.
LTC1556 Data Sheet
