Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
12(78)
4
ADC-Calibration (Voltage-Calibration)
4.1
What is ADC-calibration
For the processor to be able to control the phone in a correct way it has to know the current
battery voltage.
The processor cannot use analogue information, therefore it has to be converted from
analogue to digital configuration.
The conversion is done in the circuit N700.
The VBATT voltage input is CHSENSE-.
The voltage is then amplified, multiplexed and AD-converted before VBATT is put out on the
I
2
CDAT-bus as an 8-bit serial data word.
To make the measurement of the battery voltage exactly, is it necessary to perform a
calibration.
The calibration is performed on two voltages, 3.2 V
DC
and 4.1 V
DC
.
The corresponding ADC-values are stored in the EEPROM
ADC-values for other battery voltages are produced by interpolation of the two calibrated
voltages.
4.2
How do you perform an ADC-calibration
Start the phone in EFRA with the test program.
Go to Logic\ ADC Calibrate
When you have started ADC Calibrate following window is shown Fig. 4.1
,
telling you to
set the battery voltage on the power supply to 3.2 V
DC
.
When you have done that, click on OK.
Fig. 4.1
A new window shows up Fig. 4.2, telling you to change the battery voltage to 4.1 V
DC,
on the power supply.
When you have done that, click on OK.