1FEATURES
• Level Translator
– VCC Range of 1.65 V to 3.3 V
– VBATT Range of 2.3V to 5.5V
• Low-Dropout (LDO) Regulator
– 50-mA LDO Regulator With Enable
– 1.8-V or 2.95-V Selectable Output Voltage
– Very Low Dropout: 100 mV (Max) at 50 mA
• Control and Communication Through GPIO
Interface with Baseband Processor
• Isolated Clock Stop Mode for both SIM1 and
SIM2 cards
• ESD Protection Exceeds JESD 22
– 2000-V Human-Body Model (A114-B)
– 500-V Charged-Device Model (C101)
– 8kV HBM for SIM pins
• Package
– 20-Pin QFN (3 mm x 3 mm)

DESCRIPTION
The TXS4558 is a complete dual-supply standby Smart Identity Module (SIM) card solution for interfacing wireless
baseband processors with two individual SIM subscriber cards to store data for mobile handset applications.
It is a custom device which is used to extend a single SIM/UICC interface to be able to support two
SIM’s/UICC’s.
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,
two low-dropout (LDO) voltage regulators that have output voltages that are selectable between 2.95-V Class-B
and 1.8-V Class-C interfaces. Simple GPIO inputs are used to switch between the two SIM cards and to put it
into different modes. The voltage-level translator has two supply voltage pins. VCC sets the reference for the
baseband interface and can be operated from 1.65 V to 3.3 V. VSIM1 and VSIM2 are programmed to either
1.8 V or 2.95 V, each supplied by an independent internal LDO regulator. The integrated LDO accepts input
battery voltages from 2.3 V to 5.5 V and outputs up to 50 mA to the B-side circuitry and external Class-B or
Class-C SIM card.
The TXS4558 also incorporates shutdown sequence for the SIM card pins based on the ISO 7816-3 specification
for SIM cards. The device also has 8kV HBM protection for the SIM card pins and standard 2kV HBM protection
for all the other pins.