AN1919| Application Note
Maxim/Dallas > App Notes > BATTERY MANAGEMENT Keywords: dynamic range, current measurement, fuel gauge, battery pack, fuel gauges, DS2770, DS2761, DS2760, DS2751, DS2740, DS27xx
Mar 07, 2003
APPLICATION NOTE 1919
Increasing the Fuel Gauge Dynamic Range
The DS27xx series of fuel gauge devices from Dallas Semiconductor all specify a dynamic range over which a constant current can be measured. However, peak currents higher than this range can be measured by implementing a RC filter that can smooth the waveform into the measurable range of the device. This application note discusses how to implement this filter using a single external capacitor and then proceeds to instruct the reader on how to choose the proper capacitor value for the application.
Introduction
Figure 1. DS27XX A/D Filter Circuit. The data sheet specified maximum allowable input range for the current sensing A/D on DS27XX fuel gauge devices is displayed as a constant current value. This is not the true peak current measurable however. The A/D input of every Dallas Semiconductor fuel gauge contains an RC filter that will smooth the waveform and allow peaks greater than the specified maximum to be properly integrated. The filter capacitance is selectable to produce a waveform that uses the full range of the A/D but does not saturate its input.
Operation
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