The TXS4555 is a complete Smart Identity Module (SIM) card solution for interfacing
wireless baseband processors with a SIM card to store I/O for mobile handset applications. The
device complies with ISO/IEC Smart-Card Interface requirements as well as GSM and 3G mobile
standards. It includes a high-speed level translator capable of supporting Class-B (2.95 V) and
Class-C (1.8 V) interfaces, a low-dropout (LDO) voltage regulator that has output voltages that are
selectable between 2.95-V Class-B and 1.8-V Class-C interfaces.
Note: The Exposed center thermal pad must be connected to Ground
The device has two supply voltage pins. VCC can be operated over the full
range of 1.65 V to 3.3 V and VBATT from 2.3 to 5.5 V. VPWR is set to either
1.8 V or 2.95 V and is supplied by an internal LDO. The integrated LDO accepts input voltages as
high as 5.5 V and outputs either 1.8 V or 2.95 V at 50 mA to the B-side circuitry and to the
external SIM card. The TXS4555 enables system designers to easily interface low-voltage
microprocessors to SIM cards operating at 1.8 V or 2.95 V.
The TXS4555 also incorporates shutdown sequence for the SIM card pins based on the ISO
7816-3 specification for SIM cards. Proper shutdown of the SIM card signals helps in prevention of
corruption of data during accidental shutdown of the phone. The device also has 8kV HBM protection
for the SIM pins and standard 2kV HBM protection for all the other pins.
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