SIM_DET_WP7504

Hi

in wp7504 it is mentioned that SIM _DETECT pin requires a translation for detection

The UIM Detect signals transition:
•When a UIM is inserted — high (logic 0 to logic 1)
•When a UIM is removed — low (logic 1 to logic 0)

but as shown in the digram in the check list when sim is inserted a low (logic 1 to logic 0) will be sensed by the chip and when removed the internal pull up becomes active high (logic 0 to logic 1) both the data are conflicting and it is also mentioned that if detect is not used the pin should be connected to ground ?
please confirm


HI,
The SIM detection in WP75xx needs an inversion externally ( through a NOT gate or a simple FET). The SIM connector detect pin goes to low when a SIM is inserted and is normally high with no SIM. THe WP75xx works on an inverted logic

I am using one in my application now and have tested it to work
Regards
Shiladitya

Also remember to protect the SIM detect pin with a standalone ESD protection device. You would not want the SIM detect signal leaking voltage to an unpowered UIM_VCC.
This recommended circuit is corrected in the latest WP75xx PTS