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DETAILED DESCRIPTION

Battery Freshness Seal (TPS3619)

Power-Fail Comparator (PFI and PFO)

Backup-Battery Switchover

TPS3619-33

,, TPS3619-50

TPS3620-33, TPS3620-50

SLVS387G – APRIL 2001 – REVISED DECEMBER 2006

The battery freshness seal of the TPS3619 family disconnects the backup-battery from internal circuitry until it is

needed. This function prevents the backup-battery from being discharged unitl the final product is put to use.

The following steps explain how to enable the freshness seal mode.

2. Ground PFO

applied.

An additional comparator is provided to monitor voltages other than the nominal supply voltage. The

power-fail-input (PFI) is compared with an internal voltage reference of 1.15 V. If the input voltage falls below the

plus about 12-mV hysteresis, the output returns to high. By connecting two external resistors, it is possible to

consumption and also to assure that the current in the PFI pin can be ignored compared with the current through

the resistor network. The tolerance of the external resistors should be not more than 1% to ensure minimal

variation of sensed voltage. If the power-fail comparator is unused, PFI should be connected to ground and PFO

left unconnected.

In case of a brownout or power failure, it may be necessary to preserve the contents of RAM. If a backup battery

FUNCTION TABLE

1

1

1

0

0

1

0

0

10

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