Datasheet

FUNCTIONAL DEVICE OPERATION
BATTERY INTERFACE AND CONTROL
Analog Integrated Circuit Device Data
Freescale Semiconductor 95
MC13892
Crossing the thresholds BATTCYCL and CHGCURR will generate the interrupts CCCVI and CHGCURRI respectively. These
interrupts can be used as a simple way to implement a three-bar battery meter.
BATTERY THERMISTOR CHECK CIRCUITRY
A battery pack may be equipped with a thermistor, which value decreases over temperature (NTC). The relationship between
temperature T (in Kelvin) and the thermistor value (RT) is well characterized and can be described as RT
= R0*e^(B*(1/T-1/T0),
with T0 being room temperature, R0 the thermistor value at T0 and B being the so called B-factor which indicates the slope of
the thermistor over temperature. In order to read out the thermistor value, it is biased from GPO1 through a pull-up resistor R
PU
.
See also the ADC chapter. The battery thermistor check circuit compares the fraction of GPO1 at ADIN5 with two preset
thresholds, which correspond to 0 and 45
°C, see Table 73. Charging is generally allowed when the thermistor is within the range,
see next section for details.
CHARGE LED INDICATOR
Since normal LED control via the SPI bus is not always possible in the charging mode, an 8.0 mA max current sink is provided
at the CHRGLED pin for an LED connected to CHRGRAW.
The LED will be activated when standalone charging is started, and will remain under control of the state machine also when
the application is powered on. At the end of charge, the LED is automatically disabled. Through the CHRGLEDEN bit, the LED
can be forced on. In software controlled charging, the LED is under full control of this CHRGLEDEN bit.
Debounce Period
BATTMIN, BATTON rising edge (normal
– 32 – ms
BATTMIN, BATTON rising edge (slow)
– 1.0 – s
BATTMIN falling edge (slow)
– 1.0 – s
BATTMIN falling edge (fast)
– 1.0 – s
BATTCYCL dual edge
– 100 – ms
CHGCURR
– 1.0 – ms
Charger Detect dual edge
– 100 – ms
Table 73. Battery Thermistor Check Main Characteristics
Temperature Threshold Voltage at ADIN5
Corresponding Resistor Values Corresponding Temperature (in °C) *
Rpu RT B=3200 B=3500 B=3900
T
LOW
24/32 * GPO1
10 k 30 k -3.0 0.0 +2.0
T
HIGH
10/32 * GPO1
10 k 4.5 k +49 +46 +44
Table 74. Charge LED Drivers Main Characteristics
Parameter Condition Min Typ Max Units
Trickle LED current
CHRGLED = 2.5 V
– – 8.0 mA
CHRGLED = 0.7 V
5.0 – – mA
Notes
81. Above conditions represent respectively a USB and a collapsed charger case
Table 75. Charge LED Driver Control
CHRGLEDEN CHRGLED
0 (default) Auto
1 On
Table 72. Charger Detectors Main Characteristics (continued)
Parameter Condition Min Typ Max Units