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LM2776

SNVSA56A – MAY 2015 – REVISED FEBRUARY 2016

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Feature Description (continued)

Thermal shutdown is most often triggered by self-heating, which occurs when there is excessive power

dissipation in the device and/or insufficient thermal dissipation. LM2776 power dissipation increases with

increased output current and input voltage. When self-heating brings on thermal shutdown, thermal cycling is the

typical result. Thermal cycling is the repeating process where the part self-heats, enters thermal shutdown

(where internal power dissipation is practically zero), cools, turns on, and then heats up again to the thermal

shutdown threshold. Thermal cycling is recognized by a pulsing output voltage and can be stopped be reducing

the internal power dissipation (reduce input voltage and/or output current) or the ambient temperature. If thermal

cycling occurs under desired operating conditions, thermal dissipation performance must be improved to

accommodate the power dissipation of the LM2776.

7.3.5 Undervoltage Lockout

the input voltage drops to 2.4 V. If the input voltage rises above 2.6 V, the LM2776 resumes normal operation.

7.4 Device Functional Modes

7.4.1 Shutdown Mode

An enable pin (EN) pin is available to disable the device and place the LM2776 into shutdown mode reducing the

quiescent current to 1 µA. In shutdown, the output of the LM2776 is pulled to ground by an internal pullup current

source (approx 1.85 mA).

7.4.2 Enable Mode

Applying a voltage greater than 1.2 V to the EN pin places the device into enable mode. When unloaded, the

input current during operation is 120 µA. As the load current increases, so does the quiescent current. When

enabled, the output voltage is equal to the inverse of the input voltage minus the voltage drop across the charge

pump.