13892 datasheet(101/161 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

101

13892

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.

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.

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 83. Battery Voltage Reading Coding

Conversion Code ADDn[9:0]

Voltage at

input ADC in V

Voltage at

BATT in V

1 111 111 111

2.400

4.800

1 000 010 100

1.250

2.500

0 000 000 000

0.000

Table 84. Battery Current Reading Sequence

ADC Trigger

Signals Sampled

Signal Converted

Readout

Contents

BATT, BATT – BATTISNSCC

BATT

Channel 0

BATT

BATT – BATTISNSCC

Channel 1

BATT – BATTISNSCC

BATT, BATT – BATTISNSCC

BATT

Channel 2

BATT

BATT – BATTISNSCC

Channel 3

BATT – BATTISNSCC

BATT, BATT – BATTISNSCC

BATT

Channel 4

BATT

BATT – BATTISNSCC

Channel 5

BATT – BATTISNSCC

BATT, BATT – BATTISNSCC

BATT

Channel 6

BATT

BATT – BATTISNSCC

Channel 7

BATT – BATTISNSCC

Table 85. Battery Current Reading Coding

Conversion Code,

ADDn[9:0]

Voltage at Input, ADC in

BATT – BATTISNS in mV

Current through

20 mOhm in mA

Current Flow

0 111 111 111

1200.00

3000

From battery

0 000 000 001

2.346

0.117

5.865

From battery

0 000 000 000

1 111 111 111

-2.346

-0.117

5.865

To battery

1 000 000 000

-1200.00

-60

3000

To battery

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