BQ33100_15 Datasheet, PDF (12/67 Pages) Texas Instruments – Super Capacitor Manager

bq33100
SLUS987B – JANUARY 2011 – REVISED DECEMBER 2015
8 Detailed Description
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8.1 Overview
The bq33100 is a Super Capacitor monitor, balancing controller and overall system manger. The device can
individually monitor up to 5 series capacitors and up to 9 when monitoring the total stack.
The device can also interact with a external charging solution to provide Capacitance and Effective Series
Resistance (ESR) data on the stack.
NOTE
The following notation is used in this document, if SBS commands and Data Flash values
are mentioned within a text block:
• SBS commands are set in italic, for example: Voltage
• SBS bits and flags are capitalized, set in italic and enclosed with square brackets, for
example: [SS]
• Data Flash values are set in bold italic, for example: OV Threshold
• All Data Flash bits and flags are capitalized, set in bold italic and enclosed with square
brackets, for example: [OV]
All SBS commands, Data Flash values and flags mentioned in a chapter are listed at the
beginning of each chapter for reference.
The reference format for SBS commands is:
SBS:Command Name(Command No.):Manufacturer Access(MA No.)[Flag], for example:
SBS:Voltage(0x09), or SBS:ManufacterAccess(0x00):Seal Device(0x0020)
8.1.1 Super Capacitor Measurements
The bq33100 measures the series capacitor voltages or stack voltage, current and temperature using a delta-
sigma analog-to-digital converter (ADC). The bq33100 uses this measured data and advanced algorithms to
determine the State-of-Health and available capacitance of the Super Capacitor.
8.1.1.1 Voltage
The bq33100 has two separate modes, Normal mode and Stack mode, where measurements and taken and
managed differently. The setting of Operation Cfg [STACK] to 1 enables Stack mode otherwise the bq33100
operates in normal mode.
The bq33100 updates the individual series capacitor voltages and stack voltage at one (1) second intervals when
in Normal mode and measurers the stack voltage at one (1) second intervals when in Stack mode. The internal
ADC of the bq33100 measures the voltage, scales, and offsets, and calibrates it appropriately. To ensure an
accurate differential voltage sensing, the IC ground must be connected directly to the most negative terminal of
the Super Capacitor stack, not to the positive side of the sense resistor. This minimizes the voltage drop across
the PCB trace.
8.1.1.2 Current, Charge and Discharge Counting
The delta-sigma ADC measures the system current of the Super Capacitor by measuring the voltage drop across
a small-value sense resistor (typically 5 mΩ to 20 mΩ typical) between the SRP and SRN pins. The ADC
measures bipolar signals from –0.20 V to 0.25 V.
8.1.1.3 Device Calibration
The bq33100 requires voltage calibration to maximize accuracy of the monitoring system, the bq33100
evaluation software can perform this calibration. The external filter resistors, connected from each capacitor to
the VCx input of the bq33100, are required to be 1 kΩ.
The bq33100 can automatically calibrate its offset between the A to D converter and the input of the high voltage
translation circuit during normal operation for maximum capacitor voltage measurement accuracy.
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