FLY E185
Service Manual
CKT Confidential
Page 23 of 47
The SIMVCC is used to control the external voltage supply to the SIM card and SIMSEL
determines the regulated smart card supply voltage. SIMRST is used as the SIM card reset signal.
Besides, SIMDATA and SIMCLK are used for data exchange purpose.
There are two SIM card interface modules to support two SIM cards simultaneously. The SIM
card interface circuitry of PMU meets all ETSI and IMT-2000 SIM interface requirements. It
provides level shifting needs for low voltage GSM controller to communicate with either 1.8V or
3V SIM cards. All SIM cards contain a clock input, a reset input, and a bi-directional data
input/output. The clock and reset inputs to SIM cards are level shifted from the supply of digital
IO (Vio) of baseband to the SIM supply (Vsim). The bi-directional data bus is internal pull high to
Vsim via5K
Ω
resistor. The 2ndSIM card interface can be used for supporting another SIM card or
mobile TV. The interface pins such as SIO2, SRST2, SCLK2, can be configured as GPIO when
there is no need to use the 2ndSIM card interface. All pins that connect to the SIM card (Vsim,
SRST, SCLK, SIO) withstand over 5kV HBM (human body mode) ESD. In order to ensure proper
ESD protection, careful board layout is required.
Figure 3.4.3 Dual SIM Interface Circuit
