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BQ77904 bảng dữ liệu(PDF) 19 Page - Texas Instruments |
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BQ77904 bảng dữ liệu(HTML) 19 Page - Texas Instruments |
19 / 46 page Table 8-3. Fault Condition, State, and Recovery Methods FAULT FAULT TRIGGER CONDITION CHG DSG RECOVERY METHOD TRIGGER DELAY RECOVERY DELAY CTRC disabled CTRC disabled for deglitch delay time OFF — CTRC must be enabled for deglitch delay time tCTRDEG_ON tCTRDEG_OFF CTRD disabled CTRD disabled for deglitch delay time — OFF CTRD must be enabled for deglitch delay time OV V(Cell) rises above VOV for delay time OFF — V(Cell) drops below VOV – VHYS_OV for delay tOVn_DELAY UV V(Cell) drops below VUV for delay time — OFF V(Cell) rises above VUV + VHYS_UV for delay tUVn_DELAY OW VCX – VCX–1 < VOW for delay time OFF OFF Bad VCX recovers such that VCX – VCX–1 > VOW + VOW_HYS for delay tOWn_DELAY OCD1, OCD2, SCD (VSRP - VSRN) < VOCD1, VOCD2, or VSCD for delay time OFF OFF Recovery delay expires OR LD detects < VLDT OR Recovery delay expires + LD detects < VLDT tOCD1_DELAY, tOCD2_DELAY, tSCD_DELAY, tCD_REC OTC(1) Temperature rises above TOTC for delay time OFF — Temp drops below TOTC – TOTC_REC for delay tOTC_DELAY OTD(1) Temperature rises above TOTD for delay time OFF OFF Temp drops below TOTD – TOTD_REC for delay tOTD_DELAY UTC(1) Temperature drops below TUTC for delay time OFF — Temperature rises above TUTC + TUTC_REC for delay tUTC_DELAY UTD(1) Temp drops below TUTD for delay time OFF OFF Temp rises above TUTD + TUTD_REC for delay tUTD_DELAY (1) TUTC, TUTD, TUTC_REC, and TUTD_REC correspond to the temperature produced by VUTC, VUTD, VUTC_REC, and VUTD_REC of the selected thermistor resistance. For BQ77904 and BQ77905 devices to prevent CHG FET damage, there are times when the CHG FET may be enabled even though an OV, UTC, OTC, or CTRC low event has occurred. See the State Comparator section for details. 8.3.4 Configuration CRC Check and Comparator Built-In-Self-Test To improve reliability, the device has built in CRC check for all the factory-programmable configurations, such as the thresholds and delay time setting. When the device is set up in the factory, a corresponding CRC value is also programmed to the memory. During normal operation, the device compares the configuration setting against the programmed CRC periodically. A CRC error will reset the digital circuitry and increment the CRC fault counter. The digital reset forces the device to reload the configuration as an attempt to correct the configurations. A correct CRC check reduces the CRC fault counter. Three CRC faults counts will turn off both the CHG and DSG drivers. If FETs are opened due to a CRC error, only a POR can recover the FET state and reset the CRC fault. In addition to the CRC check, the device also has built-in-self-test (BIST) on the comparators. The BIST runs in a scheduler, and each comparator is checked for a period of time. If a fault is detected for the entire check period, the particular comparator is considered at fault, and both the CHG and DSG FETs is turned off. The BIST continues to run by the scheduler even if a BIST fault is detected. If the next BIST result is good, the FET driver resumes normal operation. The CRC check and BIST check do not affect the normal operation of the device. However, there is not a specific indication when a CRC or BIST error is detected besides turning off the CHG and DSG drivers. If there is no voltage, current, or temperature fault condition present, but CHG and DSG drivers remain off, it is possible that either a CRC or BIST error is detected. Users can power-on reset (POR) the device. 8.3.5 Fault Detection Method 8.3.5.1 Filtered Fault Detection The device detects a fault once the applicable fault is triggered after accumulating sufficient trigger sample counts. The filtering scheme is based on a simple add/subtract. Starting with the triggered sample count cleared, the counts go up for a sample that is taken across the tested condition (for example, above the fault threshold when looking for a fault) and the counts go down for a sample that is taken before the tested condition (that is, www.ti.com BQ77904, BQ77905 SLUSCM3K – APRIL 2020 – REVISED JULY 2020 Copyright © 2020 Texas Instruments Incorporated Submit Document Feedback 19 Product Folder Links: BQ77904 BQ77905 |
Số phần tương tự - BQ77904_V04 |
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Mô tả tương tự - BQ77904_V04 |
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