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LTC1555L-1.8

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

The LTC

1555L-1.8 provides power conversion and level

shifting needed for low voltage GSM and WCDMA cellular

telephones to interface with either 1.8V, 3V or 5V sub-

scriber identity modules (SIMs). The part contains a

patented buck/boost charge pump DC/DC converter* that

delivers a regulated V

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 1.8V, 3V, 5V or direct connection to the

pin.

Internal level translators allow controllers operating with

supplies as low as 1.425V to interface with 1.8V, 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 32µA 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.

■

SIM Interface in GSM Cellular Telephones

■

WCDMA SIM Interface

■

Smart Card Readers

, LTC and LT are registered trademarks of Linear Technology Corporation.

SIM Power Supply and

Level Translator

■

Buck/Boost Charge Pump Generates 1.8V, 3V or 5V

■

Input Voltage Range: 2.6V to 6V

■

Controller V

Range: 1.425V to 4.4V

■

>10kV ESD on All SIM Contact Pins

■

Short-Circuit and Overtemperature Protected

■

Meets all ETSI and IMT-2000 SIM Interface

Requirements

■

1.8V to 5V Signal Level Translators

■

Very Low Operating Current: 32µA

■

Very Low Shutdown Current: <1µA

■

Soft-Start Limits Inrush Current at Turn-On

■

1MHz Switching Frequency

■

Available in 16-Pin Narrow SSOP Package

GSM Cellular Telephone SIM Interface

CIN

RIN

DATA

DDRV

CLK

RST

I/O

= 1.8V,3V,5V

VCC

= 10mA

GND

CLK

RST

I/O

–

GND

0.1µF

1µF

LTC1555L-1.8

GSM

CONTROLLER SIM

2.6V TO 6V

1.425V TO 4.4V

2.2µF

1555L TA01

*U.S. Patent No.: 5,973,944

Summary of content (8 pages)

PAGE 1
LTC1555L-1.8 SIM Power Supply and Level Translator U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®1555L-1.8 provides power conversion and level shifting needed for low voltage GSM and WCDMA cellular telephones to interface with either 1.8V, 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.
PAGE 2
LTC1555L-1.8 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) VIN, DVCC to GND ..................................... –0.3V to 6.5V VCC to GND ...............................................– 0.3V to 6.5V Digital Inputs to GND ................................– 0.3V to 6.5V CLK, RST, I/O to GND ..................... – 0.3V to VCC + 0.3V VCC Short-Circuit Duration ............................... Indefinite Operating Temperature Range (Note 2) ..
PAGE 3
LTC1555L-1.8 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (VIN = 2.6V to 6V, DVCC = 1.425V to 4.4V, controller digital pins tied to DVCC, SIM digital pins floating, C1 = 0.1µF, COUT = 2.2µF unless otherwise noted) PARAMETER CONDITIONS MIN TYP MAX UNITS 100 nA Controller Inputs/Outputs (DVCC = 1.
PAGE 4
LTC1555L-1.8 U W TYPICAL PERFOR A CE CHARACTERISTICS IVIN vs Temperature IVIN vs VIN 50 50 IVCC = 0mA TA = 25°C IDVCC vs VDVCC 20 VIN = 3.6V IVCC = 0mA FCLK = 1MHz VCC = 5V 40 40 15 VCC = 3V TA = 85°C VCC = 3V 30 IDVCC (µA) 30 IVIN (µA) IVIN (µA) VCC = 5V VCC = 1.8V 10 TA = –40°C VCC = 1.8V TA = 25°C 20 10 20 2 3 4 5 5 10 –40 6 40 0 VIN (V) 80 1 3 2 TEMPERATURE (°C) 4 1555L • G02 VCC vs VIN 1555L • G03 VCC vs VIN VCC vs VIN 3.6 VCC = 5V IVCC = 10mA 5.
PAGE 5
LTC1555L-1.8 U U U PIN FUNCTIONS M2 (Pin 6): Mode Control Bit 2 (see Table 1). (Pin 6 was previously used for soft-start control on the LTC1555.) VIN (Pin 12): Charge Pump Input Pin. May be between 2.6V and 6V. There is no power-up sequencing requirement for VIN with respect to DVCC. M1 (Pin 7): Mode Control Bit 1 (see Table 1). VCC (Pin 13): SIM Card VCC Output. Should be connected to the SIM VCC contact. The VCC output voltage is determined by the M0-M2 pins (see Table 1).
PAGE 6
LTC1555L-1.8 U W U U APPLICATIO S I FOR ATIO The LTC1555L-1.8 performs the two primary functions necessary for low voltage controllers (e.g., GSM cellular telephone controllers, smart card readers, etc.) to communicate with 5V SIMs or smart cards. The part produces a regulated 1.8V, 3V or 5V VCC supply for the SIM, and also provides level translators for communication between the SIM and the controller. If the input source impedance is very low (< 0.5Ω), CIN may not be needed.
PAGE 7
LTC1555L-1.8 U W U U APPLICATIO S I FOR ATIO This configuration is only allowed if the controller data output pin is open drain (all SIM I/O pins are open drain). Internal pull-up resistors are provided for both the DATA pin and the I/O pin on the SIM side. The second method is to use the DDRV pin to send data to the SIM and use the DATA pin to receive data from the SIM. When the DDRV pin is not used, it should either be left floating or tied to DVCC.
PAGE 8
LTC1555L-1.8 U TYPICAL APPLICATIO WCDMA Cellular Telephone SIM Interface WCDMA CONTROLLER 1.425V TO 4.4V 1 2 3 4 5 VCC 6 7 8 VIN 2.6V TO 6V LTC1555L-1.8 CIN CLK RIN RST DATA I/O DDRV VCC DVCC VIN M2 C1 + M1 M0 SIM 16 CLK 15 RST 14 I/O 13 VCC = 1.8V,3V IVCC = 6mA 12 2.2µF 11 10 C1 – 9 GND 0.1µF 1µF GND 1555L TA02 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. GN Package 16-Lead Plastic SSOP (Narrow 0.150) (LTC DWG # 05-08-1641) 0.189 – 0.