EN

Active Data

SIM_RST

SIM_CLK

SIM_I/O

VSIM

TXS4555

SBOS550A

– FEBRUARY 2011 – REVISED MARCH 2011

www.ti.com

Figure 4. Shutdown Sequence for SIM_RST, SIM_CLK, SIM_IO and VSIM

The shutdown sequence for the SIM signals is based on the ISO 7816-3 specification. The shutdown sequence

of these signals helps to properly disable these channels and not have any corruption of data accidently. Also,

this is also helpful when the SIM card is present in a hot swap slot and when pulling out the SIM card, the orderly

shutdown of these signals help avoid any improper write/corruption of data.

When EN is taken low, the shutdown sequence happens by powering of the SIM_RST channel. Once that is

achieved, SIM_CLK, SIM_I/O and VSIM are powered sequentially one by one. There is an internal 2K pull-down

value on the SIM pins and helps to pull these channels low. The shutdown time sequence is in the order of a few

microseconds. It is important that EN is taken low before VBAT and VCC supplies go low so that the shutdown

sequence can be initiated properly.

4

Submit Documentation Feedback

Copyright

© 2011, Texas Instruments Incorporated

Product Folder Link(s): TXS4555