Battery Temperatur Measurement

The battery temperature is measured during charging. The BTEMP pin to the battery is pulled up on baseband by a 47 kohm resistor to logic supply voltage, 3.2V. The voltage on the BTEMP pin is a function of the battery pack temperature. Auxiliary A D channel 3 is used for this purpose. Inside the battery pack there is a 47 kohm NTC resistor to ground. The A D converter value can be calculated from the following formula where RNTC is the value of the NTC resistor inside the battery pack. The...

Charger Voltage Measurement

The charger voltage is measured to determine the type of charger used. MCU A D converter channel 1 is used for this purpose. The input circuitry to the charger measurement A D channel implements an LP-filter. The input voltage must be scaled before it is fed to the A D converter input. Due to the high input voltage range scaling is performed outside PSCLD, N301. The scaling factor required is 22 (22+100) 0.18. The charger voltage measurement switch is integrated into PSCLD, N301. Charger...

Battery Voltage Measurement

The battery voltage is measured using RFI2, N450 A D converter channel 0 and 7. The converter value supplied from channel 7 is measured when the transmitter is active. This measurement gives the minimum battery voltage. The value from channel 0 is measured when the transmitter is inactive. The battery voltage supplied to the A D converter input is switched off when the baseband is in power off. The battery voltage measurement voltage is supplied by PSCLD, N301 which performs scaling, the...

Charging Control Switch Functional Description

The charging switch transistor V304 controls the charging current from the charger input to the battery. During charging the transistor is forced in saturation and the voltage drop over the transistor is 0.2-0.4V depending upon the current delivered by the charger. Transistor V304 is controlled by the PWM output from N301, pin 23 via resistors R309, R308 and transistor V303. The output from N301 is of open drain type. When transistor V304 is conducting the output from N301 pin is low. In this...

External Audio

The external microphone audio signal is applied to the baseband system connector and connected to the audio block using signals XMIC and SGND. In order to improve the external audio performance the input circuitry is arranged in a sort of dual ended. A wheatstone type of bridge configuration is created by resistors R216, R217, R219 and R220. The signal is attenuated around 20 dB to not cause distortion in the microphone amplifier. The microphone signal is attenuated by resistors R216, R207 and...