The TXS02326A 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 support two SIMs/UICCs.
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 with output voltages that
are selectable between 2.95-V Class-B and 1.8-V Class-C interfaces; an integrated "fast-mode" 400
kb/s "slave" I2C control register interface, for configuration purposes;
and a 32-kHz clock input, for internal timing generation. The TXS02326A also includes a shutdown
input and a comparator input that detects battery pack removal to safely power-down the two SIM
cards. The shutdown input and comparator input are equipped with two programmable debounce counter
(i.e. BSI input and SDN input) circuits realized by an 8 bit counter.
The voltage-level translator has two supply voltage pins. VDDIO sets the reference for
the baseband interface and can be operated from 1.7-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.