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BQ2031 Datasheet(PDF) 9 Page - Texas Instruments |
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BQ2031 Datasheet(HTML) 9 Page - Texas Instruments |
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9 / 19 page  Second Difference ( ∆ 2V) Second difference is a Unitrode proprietary algorithm that accumulates the difference between successive sam- ples of VBAT. The bq2031 takes a sample and makes a termination decision at a frequency equal to 0.008 * tMTO. Fast charge terminates when the accumulated dif- ference is ≤ -8mV. Second difference is used only in the Two-Step Current algorithm, and is subject to a hold-off period (see below). Maximum Voltage Fast charge terminates when VCELL ≥ VBLK.VBLK is set per equation 2. Maximum voltage is used for fast charge termination in the Two-Step Current and Pulsed Cur- rent algorithms, and for transition from phase 1 to phase 2 in the Two-Step Voltage algorithm. This crite- rion is subject to a hold-off period. Hold-off Periods Maximum V and ∆ 2V termination criteria are subject to a hold-off period at the start of fast charge equal to 0.15 * tMTO. During this time, these termination criteria are ignored. Maximum Time-Out Fast charge terminates if the programmed MTO time is reached without some other termination shutting off fast charge. MTO is programmed from 1 to 24 hours by an R-C network on TMTO (see Figure 9) per the equa- tion: Equation 6 tMTO = 0.5 * R * C where R is in k Ω, C is in µF, and tMTO is in hours. Typi- cally, the maximum value for C of 0.1 µF is used. Fast-charge termination by MTO is a Fault only in the Pulsed Current algorithm; the bq2031 enters the Fault state and waits for a new battery insertion, at which time it begins a new charge cycle. In the Two-Step Volt- age and Two-Step Current algorithms, the bq2031 tran- sitions to the maintenance phase on MTO time-out. The MTO timer starts at the beginning of fast charge. In the Two-Step Voltage algorithm, it is cleared and re- started when the bq2031 transitions from phase 1 (cur- rent regulation) to phase 2 (voltage regulation). The MTO timer is suspended (but not reset) during the out- of-range temperature (Charge Pending) state. Maintenance Charging Three algorithms are used in maintenance charging: n Two-Step Voltage algorithm n Two-Step Current algorithm n Pulsed Current algorithm Two-Step Voltage Algorithm In the Two-Step Voltage algorithm, the bq2031 provides charge maintenance by regulating charging voltage to VFLT. Charge current during maintenance is limited to ICOND. Two-Step Current Algorithm Maintenance charging in the Two-Step Current Algo- rithm is implemented by varying the period (TP)ofa fixed current (ICOND =IMAX/5) and duration (0.2 sec- onds) pulse to achieve the configured average mainte- nance current value. See Figure 10. Maintenance current can be calculated by: Equation 7 Maintenance current I T I T COND P MAX P = ∗ = ∗ (( . ) ) (( . ) ) 02 0 04 where TP is the period of the waveform in seconds. Table 4 gives the values of P programmed by IGSEL. 9 bq2031 TM FG203112.eps VCC VSS bq2031 12 13 1 VSS VCC C R Figure 9. R-C Network for Setting MTO |
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Similar Description - BQ2031 |
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