LTC1955 Datasheet, PDF (1/20 Pages) Linear Technology – Dual Smart Card Interface with Serial Control

FEATURES
s _{Compatible with ISO7816-3 and EMV Electrical}
Specifications
s _{Power Management and Control for Two Smart}
Cards
s _{Control/Status Serial Port May be Daisy-Chained}
for Multicard Applications
s _{Automatic Shutdown on Electrical Faults}
s _{Buck/Boost Charge Pump Generates 5V, 3V or 1.8V}
Outputs (Smart Card Classes A, B and C)*
s _{Independent 5V/3V/1.8V Level Control for Both Cards}
s _{Automatic Level Translation}
s _{Supervisory Functions Prevent Smart Card Faults}
s _{Low Operating Current: 250µA Typical}
s _{Ultralow Shutdown Current}
s _{>10kV ESD on Smart Card Pins}
s
Small
32-Pin
5mm
U
×
5mm
QFN
Package
APPLICATIO S
s _{Handheld Payment Terminals}
s _{Pay Telephones}
s _{ATM Machines}
s _{POS Terminals}
s _{Computer Keyboards}
s _{Multiple S.A.M. Sockets}
LTC1955
Dual Smart Card Interface
with Serial Control
DESCRIPTIO
The LTC^®1955 provides all necessary supervisory and
power control functions for two smart cards, two S.A.M.
cards or a combination of S.A.M. and smart cards. It
provides a charge pump for battery powered applications
as well as all necessary level shifting circuitry.
The card voltages can be independently set to 1.8V, 3V or
5V. Both card interfaces include a card detection channel
with automatic debounce circuitry. To reduce wiring costs,
the LTC1955 interfaces to a microcontroller via a simple
4-wire serial interface. Multiple devices may be connected
in daisy-chain fashion so that the number of wires to the
card socket board is independent of the number of sock-
ets. Status data is returned over the same interface.
Extensive security features ensure proper deactivation
sequencing in the event of a supply fault or a smart card
electrical fault. The smart card pins can withstand greater
than 10kV ESD in-situ with no additional components.
The LTC1955 is available in a small 5mm × 5mm QFN
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*U.S. Patent No. 6,411,531
TYPICAL APPLICATIO
Deactivation Sequence
RST A
5V/DIV
CLK A
5V/DIV
I/O A
5V/DIV
V_CCA
5V/DIV
10µs/DIV
1955 G11.eps
INPUT
POWER _0.1µF
4-WIRE
COMMAND
INTERFACE
4.7µF
240k
180k
23
1
UNDERV
2
12,13 ^DVCC
PRES A
V_BATT
LTC1955
9, 10
GND
3
C8A
4
C4A
24
FAULT
5
I/O A
6
RST A
27
7
28 ^DIN
CLK A
8
26 ^DOUT
V_CCA
SCLK
25
21 ^1µF
LD
PRES B
4-WIRE
CARD
INTERFACE
29 _DATA
30
32
R_IN
SYNC
31 _ASYNC
22 _NC/NO
C⁺ C^–
I/O B ²⁰
RST B ¹⁹
CLK B ¹⁸
V_CCB ¹⁷
1µF
CPO
14
11 15
4.7µF
1µF
CARD
DETECT
SMART CARD
VENDOR CARD
1955 TA01
sn1955 1955fs
1