Datasheet

104
8024A–AVR–04/08
ATmega8HVA/16HVA
19. Coulomb Counter - Dedicated Fuel Gauging Sigma-delta ADC
19.1 Features
• Sampled System Coulomb Counter
• Low Power Sigma-Delta ADC Optimized for Coulomb Counting
• Instantaneous Current Output with 3.9 ms Conversion Time
– 13 bit Resolution (including sign bit)
– Interrupt on Instantaneous Current Conversion Complete
• Accumulate Current Output
– Programmable Conversion Time: 125/250/500/1000 ms
– 18-bit Resolution (including sign bit)
– Interrupt on Accumulation Current Conversion Complete
• Regular Current Detection Mode
– Programmable Sampling Interval: 250/500/1000/2000 ms
• Input Voltage Range ± 100mV
– Allowing Measurement of ± 10A @ 10 mΩ
• Offset canceling by input polarity switching
19.2 Overview
ATmega8HVA/16HVA features a dedicated Sigma-Delta ADC (CC-ADC) optimized for Coulomb
Counting. By sampling the voltage across an external sense resistor R
SENSE
, the CC-ADC is
used to track the flow of current going into and out of the battery cells.
Figure 19-1. Coulomb Counter Block Diagram
In normal conversion mode two different output values are provided, Instantaneous Current and
Accumulate Current. The Instantaneous Current Output has a short conversion time at the cost
Sigma Delta
modulator
Current
Comparator
Control &
Status
Registers
IRQ
8-BIT DATABUS
Regular
Current Level
Decimation
Filter
Decimation
Filter
IRQ
IRQ
R
SENSE
PI
NI
Polarity
Switcher
Instantaneous
Current
Register
Accumulate
Current
Register