STM802MM6F datasheet(19/43 Pages) STMICROELECTRONICS

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STM690A/692A/703/704/802/805/817/818/819

Operation

Doc ID 10522 Rev 10

19/43

2.12

Battery freshness seal (STM817/818/819)

The battery freshness seal disconnects the backup battery from internal circuitry and VOUT

until it is needed. This allows an OEM to ensure that the backup battery connected to VBAT

will be fresh when the final product is put to use. To enable the freshness seal:

Connect a battery to VBAT

Ground PFO

Bring VCC above the reset threshold and hold it there until reset is deasserted following

the reset timeout period and

Bring VCC down again (Figure 16)

Use the same procedure for the STM818, but ground ECON instead of PFO. Once the

battery freshness seal is enabled (disconnecting the backup battery from internal circuitry

and anything connected to VOUT), it remains enabled until VCC is brought above VRST.

Figure 15.

Using a SuperCap™

Figure 16.

Freshness seal enable waveform

AI08805

STMXXX

VBAT

VCC

VOUT

GND

RST

To external SRAM

To µP

AI08806

RST

PFO

(STM817/819)

VCC

VRST

ECON

(STM818)

trec

(Externally held at 0V)

ECON out state latched

at 1/2 trec, Freshness

Seal enabled

PFO out state latched

at 1/2 trec, Freshness

Seal Enabled

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