Stmicroelectronics Gmbh

James Chester Meador

Giovanni Gozzini

Marco Sabatini

Current drawn by the fingerprint sensor subject to electrostatic discharge events not fully dissipated by a pad ring is monitored. Upon detection of an overcurrent (e.g., an increase in the current drawn by approximately an order of magnitude) indicating that a latchup condition has occurred, power is removed from the sensor, together with all inputs to the sensor, until the latchup condition is cleared. If a processor or controller is employed by the sensor, the processor or controller is concurrently reset since a firmware crash may be induced by the latchup condition. If a parallel port or other communications connection is employed by the sensor, the overcurrent signal is employed to directly disconnect power and input signals to the sensor.

Automatic latchup recovery circuit for fingerprint sensor

An electronic device battery pack for a battery requiring cycling to prolong lifetime is divided into at least two parallel cells for which the charging state is automatically maintained. When external power is available and one or more cells is substantially discharged, the substantially discharged cell(s) are selected one at a time to be fully drained and recharged. A partially discharged but not substantially discharged cell will be left in that state until use of the electronic device has substantially discharged the cell. Once a cell has been recharged, the next substantially discharged cell is drained and recharged, and so on until all cells are fully charged. If the charging of a cell is interrupted by removal of the external power, another cell is utilized to provide power to the electronic device and recharging is resumed once the external power is restored. A device kept in a charging cradle except when being utilized may thus be used and returned to the charging cradle without adversely impacting battery life.

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Berkeley, CA, United States of America

James Chester Meador