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MCP73844 Datasheet(PDF) 11 Page - Microchip Technology |
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MCP73844 Datasheet(HTML) 11 Page - Microchip Technology |
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11 / 24 page  2004 Microchip Technology Inc. DS21823B-page 11 MCP73841/2/3/4 4.0 DEVICE OVERVIEW The MCP7384X family of devices are highly advanced, linear charge management controllers. Figure 4-1 depicts the operational flow algorithm from charge initiation to completion and automatic recharge. 4.1 Charge Qualification and Preconditioning Upon insertion of a battery or application of an external supply, the MCP7384X family of devices automatically perform a series of safety checks to qualify the charge. The input source voltage must be above the undervoltage lockout threshold, the enable pin must be above the logic-high level and the cell temperature monitor must be within the upper and lower thresholds. The cell temperature monitor applies to both the MCP73841 and MCP73842, with the qualification parameters being continuously monitored. Deviation beyond the limits automatically suspends or terminates the charge cycle. Once the qualification parameters have been met, the MCP7384X initiates a charge cycle. The charge status output is pulled low throughout the charge cycle (see Table 5-1 for charge status outputs). If the battery voltage is below the preconditioning threshold (VPTH), the MCP7384X preconditions the battery with a trickle- charge. The preconditioning current is set to approximately 10% of the fast charge regulation current. The preconditioning trickle-charge safely replenishes deeply depleted cells and minimizes heat dissipation in the external pass transistor during the initial charge cycle. If the battery voltage has not exceeded the preconditioning threshold before the preconditioning timer has expired, a fault is indicated and the charge cycle is terminated. 4.2 Constant-Current Regulation – Fast Charge Preconditioning ends and fast charging begins, when the battery voltage exceeds the preconditioning threshold. Fast charge regulates to a constant-current, IREG, based on the supply voltage minus the voltage at the SENSE input (VFCS) developed by the drop across an external sense resistor (RSENSE). Fast charge continues until the battery voltage reaches the regulation voltage (VREG); or until the fast charge timer expires. In this case, a fault is indicated and the charge cycle is terminated. 4.3 Constant-Voltage Regulation When the battery voltage reaches the regulation voltage (VREG), constant-voltage regulation begins. The MCP7384X monitors the battery voltage at the VBAT pin. This input is tied directly to the positive terminal of the battery. The MCP7384X is offered in four fixed-voltage versions for single or dual series cell battery packs with either coke or graphite anodes: - 4.1V (MCP73841-4.1, MCP73843-4.1) - 4.2V (MCP73841-4.2, MCP73843-4.2) - 8.2V (MCP73842-8.2, MCP73844-8.2) - 8.4V (MCP73842-8.4, MCP73844-8.4) 4.4 Charge Cycle Completion and Automatic Re-Charge The MCP7384X monitors the charging current during the constant-voltage regulation phase. The charge cycle is considered complete when the charge current has diminished below approximately 7% of the regulation current (IREG) or the elapsed timer has expired. The MCP7384X automatically begins a new charge cycle when the battery voltage falls below the recharge threshold (VRTH), assuming all the qualification parameters are met. |
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Similar Description - MCP73844 |
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