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BQ2002GSNTR Datasheet(PDF) 5 Page - Texas Instruments |
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BQ2002GSNTR Datasheet(HTML) 5 Page - Texas Instruments |
5 / 15 page VLBAT = 0.175 ∗ VCC ±20% The valid temperature range is VTS >VHTF where VHTF = 0.6 ∗ VCC ±5%. If the battery voltage or temperature is outside of these limits, the IC pulse-trickle charges until the next new charge cycle begins. If VMCV <VBAT <VPD (see “Low-Power Mode”) when a new battery is inserted, a delay of 0.35 to 0.9s is imposed before the new charge cycle begins. Fast charge continues until termination by one or more of the five possible termination conditions: n Peak voltage detection (PVD) n Negative delta voltage (- ∆V) n Maximum voltage n Maximum temperature n Maximum time PVD and - ∆V Termination There are two modes for voltage termination, depending on the state of TM. For - ∆V (TM = high), if VBAT is lower than any previously measured value by 12mV ±3mV, fast charge is terminated. For PVD (TM = low or mid), a de- crease of 2.5mV ±2.5mV terminates fast charge. The PVD and - ∆Vtests are valid in the range 1V < VBAT <2V. Synchronized Voltage Sampling Voltage sampling at the BAT pin for PVD and - ∆V termi- nation may be synchronized to an external stimulus us- ing the INH input. Low-high-low input pulses between 100ns and 3.5ms in width must be applied at the INH pin with a frequency greater than the “maximum syn- chronized sampling period” set by the state of the TM pin as shown in Table 1. Voltage is sampled on the fal- ling edge of such pulses. If the time between pulses is greater than the synchro- nizing period, voltage sampling “free-runs” at once every 17 seconds. A sample is taken by averaging together voltage measurements taken 57 µs apart. The IC takes 32 measurements in PVD mode and 16 measurements in - ∆V mode. The resulting sample periods (9.17 and 18.18ms, respectively) filter out harmonics centered around 55 and 109Hz. This technique minimizes the ef- fect of any AC line ripple that may feed through the power supply from either 50 or 60Hz AC sources. If the INH input remains high for more than 12ms, the voltage sample history kept by the IC and used for PVD and - ∆V termination decisions is erased and a new his- tory is started. Such a reset is required when transition- ing from free-running to synchronized voltage sampling. The response of the IC to pulses less than 100ns in width or between 3.5ms and 12ms is indeterminate. Tol- erance on all timing is ±12%. Voltage Termination Hold-off A hold-off period occurs at the start of fast charging. During the hold-off time, the PVD and - ∆V terminations are disabled. This avoids premature termination on the voltage spikes sometimes produced by older batteries when fast-charge current is first applied. Maximum voltage and temperature terminations are not affected by the hold-off period. Maximum Voltage, Temperature, and Time Any time the voltage on the BAT pin exceeds the maxi- mum cell voltage,VMCV, fast charge or optional top-off charge is terminated. Maximum temperature termination occurs anytime the voltage on the TS pin falls below the temperature cut-off threshold VTCO where VTCO = 0.5 ∗ VCC ± 5%. Maximum charge time is configured using the TM pin. Time settings are available for corresponding charge rates of C/2, 1C, and 2C. Maximum time-out termina- tion is enforced on the fast-charge phase, then reset, and enforced again on the top-off phase, if selected. There is no time limit on the trickle-charge phase. Top-off Charge An optional top-off charge phase may be selected to follow fast charge termination for 1C and C/2 rates. This phase may be necessary on NiMH or other bat- tery chemistries that have a tendency to terminate charge before reaching full capacity. With top-off en- abled, ch arging continues a t a r educed r a t e after fast-charge termination for a period of time selected by the TM pin. (See Table 1.) During top-off, the CC pin is modulated at a duty cycle of 73ms active for every 1097ms inactive. This modulation results in an average rate 1/16th that of the fast charge rate. Maxi- mum voltage, time, and temperature are the only ter- mination methods enabled during top-off. Pulse-Trickle Charge Pulse-trickle is used to compensate for self-discharge while the battery is idle in the charger. The battery is pulse-trickle charged by driving the CC pin active once every 1.17s for the period specified in Table 1. This re- sults in a trickle rate of C/32. TM Pin The TM pin is a three-level pin used to select the charge timer, top-off, voltage termination mode, trickle 5 bq2002E/G |
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