A/D Channels - Nokia RH-9 Series Ccs Technical Documentation

CCS Technical Documentation

A/D Channels

The UEM contains the following A/D converter channels that are used for several mea-
surement purposes. The general slow A/D converter is a 10 bit converter using the UEM
interface clock for the conversion. An interrupt will be given at the end of the measure-
ment.
The UEM's 11-channel analog to digital converter is used to monitor charging functions,
battery functions, voltage levels in external accessory detection inputs, user interface
and RF functions.
When the conversion is started the converter input is selected. Then the signal process-
ing block creates a data with MSB set to '1' and others to '0'. In the D/A converter this
data controls the switches which connect the input reference voltage (VrefADC) to the
resistor network. The generated output voltage is compared with the input voltage under
measurement and if the latter is greater, MSB remains '1' else it is set '0'. The following
step is to test the next bit and the next., until LSB is reached. The result is then stored to
ADCR register for UPP to read.
The monitored battery functions are battery voltage (VBATADC), battery type (BSI) and
battery temperature (BTEMP) indication.
The battery type is recognized through a resistive voltage divider. In phone there is a
100kOhm pull up resistor in the BSI line and the battery has a pull down resistor in the
same line. Depending on the battery type the pull down resistor value is changed. The
battery temperature is measured equivalently except that the battery has a NTC pull
down resistor in the BTEMP line.
KEYB1&2 inputs are made for keyboard scanning purposes. These inputs are also routed
internally to the miscellaneous block. KEYB1&2 inputs are not used In NHM-8, and the
connected interrupts must be kept disabled by SW.
The HEADINT and HOOKINT are external accessory detection inputs used for monitoring
voltage levels in these inputs. They are routed internally from the miscellaneous block
and they are connected to the converter through a 2:1 multiplexer.
PATEMP and VCXOTEMP channels are not used as originally intended. PATEMP input is
used for detection of accessory covers (CTI), VCXOTEMP is not used in NHM-8.
Characteristics
Number of bits
Integral non linearity
Differential non linearity
Conversion time
Issue 1 11/02
Table 24: Slow A/D converter characteristics
Min Typ
10
- -
- -
- -
ãNokia Corporation
System Module & UI
Max Unit
bits
+/- 2 LSB
+/- 2.5 LSB
µs
11
RH-9
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