13892 datasheet(103/161 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

103

13892

FUNCTIONAL DEVICE OPERATION

ADC SUBSYSTEM

CHANNEL 5 ADIN5 AND BATTERY THERMISTOR AND BATTERY DETECT

On channel 5, ADIN5 may be used as a general purpose unscaled input, but in a typical application, ADIN5 is used to read

out the battery pack thermistor. The thermistor will have to be biased with an external pull-up to a voltage rail greater than the

ADC input range. In order to save current when the thermistor reading is not required, it can be biased from one of the general

purpose IO's such as GPO1. A resistor divider network should assure the resulting voltage falls within the ADC input range in

particular when the thermistor check function is used, see Battery Thermistor Check Circuitry.

When the application is on and supplied by the charger, a battery removal can be detected by a battery thermistor presence

check. When the thermistor terminal becomes high-impedance, the battery is considered being removed. This detection function

is available at the ADIN5 input and can be enabled by setting the BATTDETEN bit. The voltage at ADIN5 is compared to the

output voltage of the GPO1 driver, and when the voltage exceeds the battery removal detect threshold, the sense bit

BATTDETBS is made high and after a debounce the BATTDETBI interrupt is generated.

CHANNEL 6 ADIN6 AND COIN CELL VOLTAGE

On channel 6, ADIN6 may be used as a general purpose unscaled input.

In addition, on channel 6, the voltage of the coin cell connected to the LICELL pin can be read (LICON=1). Since the voltage

range of the coin cell exceeds the input voltage range of the ADC, the LICELL voltage is first scaled as V(LICELL)*2/3. In case

the voltage at LICELL drops below the coin cell disconnect threshold (see Clock Generation and Real Time Clock), the voltage

at LICELL can still be read through the ADC.

CHANNEL 7 ADIN7 AND ADIN7B, UID AND DIE TEMPERATURE

On channel 7, ADIN7 may be used as a general purpose unscaled input (ADIN7DIV = 0) or as a divide by 2 scaled input

(ADIN7DIV = 1). The latter allows converting signals that are up to twice the ADC converter core input range. In a typical

application, an ambient light sensor is connected here.

A second general purpose input ADIN7B is available on channel 7. This input is muxed on the GPO4 pin. The input voltage

can be scaled by setting the ADIN7DIV bit. In the application, a second ambient light sensor is supposed to be connected here.

Note that the GPO4 will have to be configured to allow for the proper routing of GPO4 to the ADC, see General Purpose Outputs.

In addition, on channel 7, the voltage of the USB ID line connected to the UID pin can be read. Since the voltage range of the

ID line exceeds the input voltage range of the ADC, the UID voltage is first scaled as V(UID)/2.

Also on channel 7, the die temperature can be read out. The relation between the read out code and temperature is given in

Table 93.

Table 90. Battery Removal Detect Specification

Parameter

Condition

Min

Typ

Max

Units

Battery Removal Detect Threshold(72)

31/32 * GPO1

Notes

72.

This is equivalent to a 10 kOhm pull-up and a 10 kOhm thermistor at -35 °C.

Table 91. Coin Cell Voltage Reading Coding

Conversion Code

ADDn[9:0]

Voltage at ADC input (V)

Voltage at LICELL (V)

1 111 111 111

2.400

3.6

1 000 000 000

1.200

1.8

0 000 000 000

0.000

Table 92. UID Voltage Reading Coding

Conversion Code

ADDn[9:0]

Voltage at ADC input (V)

Voltage at UID (V)

1 111 111 111

2.400

4.80 - 5.25

0 000 000 000

0.000

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