Single Interface Chip Controls Two Smart Cards – Design Note 289
Steven Martin
Introduction
There are considerable challenges to smart card interfacing, including various voltage levels (both input and
output) and stringent fault handling requirements. To
produce a robust card reading system, designers must
comply with extensive and often difficult software as
well as hardware standards. Furthermore, there are
other complications like in-circuit ESD and pin-to-pin
shorts to contend with.
The LTC В®1955 dual smart card interface provides all
of the required power management, control, ESD and
fault detection circuitry for two smart cards. Employing
a voltage doubling charge pump and two low dropout
linear regulators, this device generates two independent levels of either 5V, 3V or 1.8V from a 2.7V to 5.5V input. Both channels have the required pins to support
the EMV (Europay, MasterCard, Visa) and the ISO7816
smart card standards. One channel has extra control
pins (smart card contact pad locations C4 and C8)
to support existing memory cards. The entire chip is
controlled by a microcontroller-friendly serial interface.
Features
The LTC1955 includes considerable security and functionality, yet remains easy to use. Two independent
circuits detect the presence or absence of a smart …