FUNCTIONAL DEVICE OPERATION
BATTERY INTERFACE AND CONTROL
Table 72. Charger Detectors main characteristics
Parameter
Charger Valid
Condition
Min
Typ
3.8
-
Max
Units
V
CHRGRAW
-
10
-
-
50
-
CHGCURR Threshold
CHRGISNS-BPSNS, current from charger
BATTMIN, BATTON rising edge (normal
BATTMIN, BATTON rising edge (slow)
BATTMIN falling edge (slow)
BATTMIN falling edge (fast)
BATTCYCL dual edge
mA
ms
s
32
-
1.0
1.0
1.0
100
1.0
100
-
-
-
s
Debounce Period
-
-
s
-
-
ms
ms
ms
CHGCURR
-
-
Charger Detect dual edge
-
-
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 3-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 RPU
.
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.
Table 73. Battery Thermistor Check Main Characteristics
Corresponding Resistor Values
Corresponding Temperature (in °C) *
Temperature Threshold
Voltage at ADIN5
Rpu
10 k
10 k
RT
B=3200
-3.0
B=3500
0
B=3900
+2.0
Tlow
24/32 * GPO1
10/32 * GPO1
30 k
45 k
Thigh
+49
+46
+44
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.
Table 74. Charge LED Drivers Main Characteristics
Parameter
Trickle LED current
Condition
CHRGLED = 2.5 V
CHRGLED = 0.7 V
Min
-
Typ
Max
8.0
-
Units
mA
-
-
5.0
mA
Notes
69. Above conditions represent respectively a USB and a collapsed charger case
Table 75. Charge LED Driver Control
CHRGLEDEN
0 (default)
1
CHRGLED
Auto
On
13892
Analog Integrated Circuit Device Data
Freescale Semiconductor
94
FREESCALE [ Freescale ]
