
Analog Integrated Circuit Device Data
Freescale Semiconductor
38
PC34708
Functional Block Requirements and Behaviors
Battery Management Block Description and Application Information
7.1.3.8
Coulomb Counter
As indicated previously, the current in and out of the battery can be read out through the general purpose ADC as a voltage drop
over the R1 sense resistor. Together with battery voltage reading, the battery capacity can be estimated. A more accurate battery
capacity estimation can be obtained by using the integrated Coulomb Counter.
The Coulomb Counter (or CC) monitors the current flowing in/out of the battery by integrating the voltage drop across the battery
current sense resistor R1, followed by an A to D conversion. The result of the A to D conversion is used to increase/decrease
the contents of a counter that can be read out by software. This function will require a 10
μF output capacitor to perform a first
order filtering of the signal across R1. Due to the sampling of the A to D converter and the filtering applied, the longer the software
waits before retrieving the information from the CC, the higher the accuracy. The capacitor will be connected between the CFP
Table 31. Charge LED Drivers Period Control
CHRGLEDxPER[1:0]
Repetition Rate
Units
00
256
Hz
01
8
Hz
10
1
Hz
11
1/2
Hz
Table 32. Charge LED Modes in Standalone Mode
LED Mode
Color
Repetition
Rate (Hz)
Duty
cycle
Current
(mA)
Ramp
Charger off
Both off
1.0
Off
6.0
Off
Charging
Red on
steady state
1.0
32/32
6.0
Off
Charging
fault
Red flashing
1.0
16/32
6.0
Off
Charge
complete
Green on
steady state
1.0
32/32
6.0
Off
Table 33. Charge LED Driver Electrical Specifications
Characteristics noted under conditions BP = 3.6 V, VBUS = 5.0 V, -40°C ≤ TA ≤ 85°C, unless otherwise noted. Typical values at
BP = 3.6 V and TA = 25°C under nominal conditions, unless otherwise noted.
Symbol
Characteristic
Min
Typ
Max
Unit
Notes
Charge LED Driver
Absolute Accuracy
-
30
%
Matching - At 1.0 V, 12 nA
-
3.0
%
Leakage - CHRGLAEDxDC [5:0]=000000
-
1.0
μA