BQ2023 Datasheet, PDF (8/27 Pages) Texas Instruments – SINGLE-WIRE ADVANCED BATTERY MONITOR IC FOR CELLULAR AND PDA APPLICATIONS

bq2023
SINGLEĆWIRE ADVANCED BATTERY MONITOR IC
FOR CELLULAR AND PDA APPLICATIONS
SLUS480B – MAY 2001
APPLICATION INFORMATION
functional description
The bq2023 measures the differential voltage drop across a low-value series sense resistor between the
negative terminal of the battery and the battery-pack ground contact. An internal VFC (voltage-to-frequency
converter) converts this voltage into charge and discharge counts. The VFC is capable of resolving signals down
to 3.05 µV. By using the accumulated counts in the charge, discharge, and self-discharge registers, an
intelligent host controller can determine battery state-of-charge information. To improve accuracy, the bq2023
automatically self-calibrates every hour and continuously compensates offset errors in the VFC every hour.
Access to the registers and control of the bq2023 is accomplished through a single-wire interface command
protocol which includes placing the device in the low-power mode, hardware register reset, and flash
programming.
charge and discharge count operation
Table 1 shows the main counters and registers of the bq2023. The bq2023 accumulates charge and discharge
counts into two count registers, the discharge count register (DCR) and the charge count register (CCR). The
DCR or CCR independently counts depending on the signal between pins SRP and SRN.
During discharge, the DCR and the discharge time counter (DTC) are active. If (V_SRP–V_SRN) is less than zero,
indicating a discharge, the DCR counts at a rate equivalent to one count per 3.05 µV-hr, and the DTC counts
at 1.1378 counts per second (4096 counts = 1 hour). For example, if it is assumed that no rollover of the DTC
register is incipient, a negative 24.42 mV signal between pins SRP and SRN produces 8000 DCR counts and
4096 DTC counts each hour.
During charge, the CCR and the charge time counter (CTC) are active. If (V_SRP–V_SRN) is greater than zero,
indicating a charge, the CCR counts at a rate equivalent to one count per 3.05 µV-hr, and the CTC counts at
1.1378 counts per seconds. In this case a +24.42mV signal produces 8000 CCR counts and 4096 CTC counts
(assuming no rollover) each hour.
The DTC and the CTC are 16-bit registers, which roll over at FFFF hex. If a rollover occurs, the corresponding
bit in the mode register is set, and the counter increments at 1/256 of the normal rate (16 counts per hour).
For self-discharge calculation, the self-discharge count register (SCR) counts at a rate equivalent to 1 count
every hour at a nominal 25°C and doubles approximately every 10°C up to 60°C. The SCR count rate is halved
every 10°C below 25°C down to 0°C. The value in SCR is useful in determining an estimation of the battery
self-discharge based on capacity and storage temperature conditions.
NAME
DCR
CCR
SCR
DTC
CTC
Table 1. bq2023 Counters
DESCRIPTION
Discharge count register
Charge count register
Self-discharge count register
Discharge time counter
Charge time counter
RANGE
V(SR) < VSS (Maximum = –100 mV) 3.05 µVh/LSB
V(SR) >VSS (Maximum = 100 mV) 3.05 µVh/LSB
1 count/hour at 25°C
1 count/0.8789s if STD is clear
1 count/225s if STD is set
1 count/0.8789s if STC is clear
1 count/225s if STC is set
RAM SIZE
16-bit
16-bit
16-bit
16-bit
16-bit
8
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