# Wp7609 does not enable uim\_vcc

**URL:** <https://forum.sierrawireless.com/t/wp7609-does-not-enable-uim-vcc/17560>\
**Category:** IoT Modules\
**Created:** [September 12, 2019, 6:34pm UTC](https://forum.sierrawireless.com/t/wp7609-does-not-enable-uim-vcc/17560 "2019-09-12T18:34:34Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![rochaf](https://avatars.discourse-cdn.com/v4/letter/r/b5e925/32.png) [@rochaf](https://forum.sierrawireless.com/u/rochaf)\
**Post date:** [September 12, 2019, 6:34pm UTC](https://forum.sierrawireless.com/t/wp7609-does-not-enable-uim-vcc/17560/1 "2019-09-12T18:34:34Z")

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The Sierra WP7609 is not enabling the SIM CARD power supply (pin 26 - UIM VCC) properly in our prototype. We noted that right after the WP7609 is turned on, it tries to enable the UIM\_VCC voltage (1.8V) for some seconds (verified with oscilloscope) and than it turns this pin off (0 volts). We noted that when the SIM CARD is inserted in the SIM CARD HOLDER, the pin 64 (UIM\_DET) receives the logic transition from 0 to 1, and at this moment the WP7609 enables the UIM\_VCC voltage for some seconds, than disables it, and at following, enables the SIM RESET signal (pin 29 - UIM\_RESET\_N), putting this pin in low level state (0 volts).

After this, if we force a transition from logic 1 to 0 at the pin UIM\_DET, the UIM\_VCC pin is enabled for some seconds, and then is turned off again. We verified that the module is activated, because it answers normally to AT commands sent with minicom.

Could anyone please help me with this issue?

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**Author:** ![anthonynanas101](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@anthonynanas101](https://forum.sierrawireless.com/u/anthonynanas101)\
**Post date:** [May 23, 2020, 3:36pm UTC](https://forum.sierrawireless.com/t/wp7609-does-not-enable-uim-vcc/17560/2 "2020-05-23T15:36:33Z")

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Did you get a response on this? I am having the same problem

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**Author:** ![rochaf](https://avatars.discourse-cdn.com/v4/letter/r/b5e925/32.png) [@rochaf](https://forum.sierrawireless.com/u/rochaf)\
**Post date:** [May 25, 2020, 5:53pm UTC](https://forum.sierrawireless.com/t/wp7609-does-not-enable-uim-vcc/17560/3 "2020-05-25T17:53:39Z")

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Hello Anthony,

After some review, we found that the SIM CARD TVS diodes were wrongly assembled in our PCB. They were inverted. We reassembled them and the UIM\_VCC became properly enabled.

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**Author:** ![anthonynanas101](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@anthonynanas101](https://forum.sierrawireless.com/u/anthonynanas101)\
**Post date:** [May 25, 2020, 11:18pm UTC](https://forum.sierrawireless.com/t/wp7609-does-not-enable-uim-vcc/17560/4 "2020-05-25T23:18:26Z")

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Thanks, appreciate the feedback.

My issue is totally different. It seems that the modem doesn’t really play well with the specific SIM card. All other modems validated can read the SIM card and the WP7609 under test can also read publicly available SIM cards. SIM card tested is used in a private telecom environment.