Transient/Esd Protection; Off Current Draw - Ericsson EF738 Service Manual

Technical Description

Transient/ESD Protection

Diodes are used for ESD protection on the System Connector outputs. The inputs
have got resistors between the System Connector and the ASIC input ports. Capaci-
tors on DCIO prevent spikes caused by charger cable inductance when the charge
switch is turned off. They also protect MIA and the FET-switch from ESD and pro-
vide de-coupling for voltage ripple. A capacitor and a varistor provide de-coupling
and high-voltage / ESD protection on the battery voltage.

Off Current Draw

The current draw when the phone is off should be as low as possible in order to pre-
vent low batteries from being too heavily discharged. The only components directly
connected to the battery which may draw current when the phone is off are MIA, a
low voltage detector, and the regulators.
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