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SI9731 Datasheet(PDF) 9 Page - Vishay Siliconix |
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SI9731 Datasheet(HTML) 9 Page - Vishay Siliconix |
9 / 10 page Document Number: 71321 S-60869-Rev. B, 22-May-06 www.vishay.com 9 Vishay Siliconix Si9731 DETAIL OPERATIONAL DESCRIPTION 4.1 VTAP The Si9731’s internal feedback resistors are set to provide 4.2 V charge termination at VBAT+ output if the 4.1 VTAP is left open circuit. Connecting the 4.1 VTAP to VBAT+ configures Si9731 for 4.1 V charge termination at VBAT+. This feature allows Si9731 to accommodate Li-ion batteries requiring 4.1 V or 4.2 V charge termination. Caution: the 4.1 VTAP should not be connected to ground or any other voltage source as this will cause the Si9731 to operate open loop and can result in over charging the battery! Feedback Disconnect Switch The Si9731 includes a feedback disconnect switch (Q5 in Figure 1) connected in series with the device’s internal feed- back resistor string. The 42 k Ω feedback resistor string is connected to ground when both the internal "OK to Charge" signal and the CVMODE pin are at logic high, providing feed- back voltage to Si9731’s error amplifier. This action helps prevent the Si9731 from discharging the battery. CHARGERPRESENT and CHARGERPOWERON CHARGERPRESENT and CHARGERPOWERON are open drain outputs, each requiring an external pull-up resistor. CHARGERPRESENT pin goes low with CHARGERPRE- SENTIN pin goes high, signaling the processor that a charger has been inserted. CHARGERPOWERON Pin goes low when CHARGERPOWERONIN Pin is high, charger volt- age is not in UVLO and the battery voltage has increased to above 3.4 V, turning on the system power supply since the battery has been charged up to minimum operating voltage. Input Over-Voltage Detector The external dc source connected to the VCHARGER pin should be at 12 V or less. In the unlikely event that the volt- age at VCHARGER pin is at or above 12.8 V (typical), Si9731’s internal over voltage detector will turn off MOSFETs Q1, Q2, and Q5 and disable charging. Thermal Shutdown Si9731 also includes a thermal protection circuit that sus- pends charging through Q1 and Q2 when die temperature exceeds 130 °C due to overheating. Once the die tempera- ture cools to below 120 °C, the charging will resume. Shutdown Si9731 can be completely turned off by applying 0.4 V or less to the device’s ON/OFF pin. In shutdown mode, Si9731 draws less than 1 µA quiescent current with charger voltage below UVLO, and draws 500 µA when charger voltage is above UVLO. The device is enabled by applying 1.5 V to 12 V at the ON/OFF pin. In applications where the device will always remain enabled, the ON/OFF pin may be connected to the VCHARGER pin. Si9731’s shutdown circuitry includes hysteresis, as such the device will operate properly even if a slow moving signal is applied to the ON/OFF pin. When the device is enabled, the battery voltage sense circuitry draws approximately 25 µA from VBAT. OK to Charge (OTC) Si9731 also includes an internal signal that enables both trickle charge mode and fast charge mode operations, the "OK to Charge" (or OTC) signal. The OTC signal is at logic high if all of the following are satisfied: 1. Battery voltage is below 5 V 2. Charger voltage is greater than 2.6 V but below 12.8 V 3. VCHARGER > VBAT + 40 mV when MAINCHARGEEN = Low VCHARGER > VBAT - 40 mV when MAINCHARGEEN = High 4. ON/OFF pin is at logic high. In order to charge the battery in any manner, the OTC signal has to be high. Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon Tech- nology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and reliability data, see http://www.vishay.com/ppg?71321. |
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