User Guide

Retu handles SIM card detection and the detection method is based on battery removal trough the BSI line.

Due to location of the SIM card, removal of the battery causes quick power down of the SIM IF. The Retu SIM1

interface supports both the 1.8V and 3.0V SIM cards.

Battery interface

The battery interface supports a 3-pole battery interface. The interface consists of three connectors: VBAT,

BSI and GND.

The BSI line is used to recognize the battery capacity by a battery internal pull down resistor.

Figure 72 Battery pin order

Battery temperature is estimated by measuring separate battery temperature NTC via the BTEMP line.

For service purposes, the device SW can be forced into local mode by using pull down resistors connected to

the BSI line.

RM-86

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