LTC1555L
SIM Power Supply and
Level Translator
FEATURES
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DESCRIPTIO
Buck/Boost Charge Pump Generates 3V or 5V
Input Voltage Range: 2.6V to 6V
Controller V
CC
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
The LTC
®
1555L 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 V
CC
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 V
IN
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*U.S. Patent No.: 5,973,944
APPLICATIO S
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SIM Interface in GSM Cellular Telephones
Smart Card Readers
TYPICAL APPLICATIO
GSM Cellular Telephone SIM Interface
GSM
CONTROLLER
V
IN
2.6V TO 6V
16
15
14
13
12
11
0.1µF
1µF
GND
2.2µF
CLK
RST
I/O
V
CC
I
VCC
=
10mA
OUTPUT VOLTAGE
MODES
V
CC
= 3V
V
CC
= 5V
V
CC
* = V
IN
*ACTUAL V
CC
WILL
DEPEND ON OUTPUT
CURRENT IN THIS MODE
1555L TA01
1.425V TO 4.4V
1
2
3
4
LTC1555L
CIN
RIN
DATA
DDRV
DV
CC
N/C
M1
M0
CLK
RST
I/O
V
CC
V
IN
C1
+
SIM
V
CC
5
6
7
8
10
C1
–
GND
9
U
U
U
1
LINER [ LINEAR TECHNOLOGY ]
