Datasheet ZXCT1010 (Diodes) - 5

A Product Line of Diodes Incorporated ZXCT1010 Application Information
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Li-ion Charger Circuit:
The figure below shows the ZXCT1010 supporting the Benchmarq bq2954 Charge Management IC. Most of the support components for the bq2954 are omitted for clarity. This design also uses the Zetex FZT789A high current Super-b PNP as the switching transistor in the DC-DC step down converter and the FMMT451 as the drive NPN for the FZT789A. The circuit can be configured to charge up to four Li-ion cells at a charge current of 1.25A. Charge can be terminated on maximum voltage, selectable minimum current, or maximum time out, switching frequency of the PWM loop is approximately 120kHz.
Bi-Directional Current Sensing:
The ZXCT1010 can be used to measure current bi-directionally, if two devices are connected as show below: If the voltage V1 is positive with respect to the voltage V2 the lower device will be active, delivering a proportional output current to Rout. Due to the polarity of the voltage across RSENSE, the upper device will be inactive and will not contribute to the current delivered to Rout. When V2 is more positive than V1, current will be flowing in the opposite direction, causing the upper device to be active instead. Non-linearity will be apparent at small values of VSENSE due to offset current contribution. Devices can use separate output resistors if the current direction is to be monitored independently. ZXCT1010 5 of 8 March 2014 Document number: DS33442 Rev. 11 - 2
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