TPS3619-33-EP, TPS3619-50-EP

TPS3620-33-EP, TPS3620-50-EP

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SGLS350C – JULY 2006 – REVISED SEPTEMBER 2010

DETAILED DESCRIPTION

Battery Freshness Seal (TPS3619)

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 until the final product is put to use. The

following steps explain how to enable the freshness seal mode.

2. Ground PFO

applied.

Power-Fail Input/Output Comparator (PFI and PFO)

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

compared with an internal voltage reference of 1.15 V. If the input voltage falls below the power-fail threshold

sum of both resistors should be about 1 M

Ω, to minimize power consumption and also to ensure 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.

Backup-Battery Switchover

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

Table 2. FUNCTION TABLE

1

1

1

0

0

1

0

0

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Product Folder Link(s): TPS3619-33-EP TPS3619-50-EP TPS3620-33-EP TPS3620-50-EP