FUNCTIONAL DEVICE OPERATION
ADC SUBSYSTEM
DEDICATED READINGS
CHANNEL 0 BATTERY VOLTAGE
The battery voltage is read at the BATT pin at channel 0. The battery voltage is first scaled as V(BATT)/2 in order to fit the
input range of the ADC.
Table 83. Battery Voltage Reading Coding
Voltage at
input ADC in V
Voltage at
BATT in V
Conversion Code ADDn[9:0]
1 111 111 111
1 000 010 100
0 000 000 000
2.400
1.250
0.000
4.800
2.500
0.000
CHANNEL 1 BATTERY CURRENT
The current flowing out of and into the battery can be read via the ADC, by monitoring the voltage drop over the sense resistor
between BATT and BATTISNSCC. This function is enabled by setting BATTICON = 1.
The battery current can be read either in multiple channel mode or in single channel mode. In both cases, the battery terminal
voltage at BATT, and the voltage difference between BATT and BATTISNS, are sampled simultaneously but converted one after
the other. This is done to effectively perform the voltage and current reading at the same time. In multiple channel mode, the
converted values are read at the assigned channel. In single channel mode and ADA1[2:0] = 001, the converted result is
available in 4 pairs of battery voltage and current reading as shown in Table 84.
Table 84. Battery Current Reading Sequence
ADC Trigger
Signals Sampled
Signal Converted
BATT
Readout
Channel 0
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Contents
BATT, BATT – BATTISNSCC
BATT
0
1
2
3
4
5
6
7
-
BATT – BATTISNSCC
BATT
BATT – BATTISNSCC
BATT
BATT, BATT – BATTISNSCC
-
BATT – BATTISNSCC
BATT
BATT – BATTISNSCC
BATT
BATT, BATT – BATTISNSCC
-
BATT – BATTISNSCC
BATT
BATT – BATTISNSCC
BATT
BATT, BATT – BATTISNSCC
-
BATT – BATTISNSCC
BATT – BATTISNSCC
If the BATTICON bit is not set, the ADC will return a 0 reading for channel 1.
The voltage difference between BATT and BATTISNS is first amplified to fit the ADC input range as V(BATT-BATTISNS)*20.
Since battery current can flow in both directions, the conversion is read out in 2's complement format. Positive readings
correspond to the current flow out of the battery, and negative readings to the current flowing into the battery.
Table 85. Battery Current Reading Coding
Conversion Code,
ADDn[9:0]
Voltage at Input, ADC in
mV
Current through
20 mOhm in mA
BATT – BATTISNS in mV
Current Flow
0 111 111 111
0 000 000 001
0 000 000 000
1 111 111 111
1 000 000 000
From battery
From battery
-
1200.00
2.346
0
60
0.117
0
3000
5.865
0
To battery
To battery
-2.346
-1200.00
-0.117
-60
5.865
3000
13892
Analog Integrated Circuit Device Data
Freescale Semiconductor
101
FREESCALE [ Freescale ]
