EM6812F2TP24B datasheet(21/81 Pages) EMMICRO

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EM6812

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BO and SVLD consumption adder

IVDD=f(Temp)

-40

-20

2040

6080 [°C]

BO and SVLD consumption adder

IVDD=f(VDD)

3456 [V]

7.5

BrownOut reset

The BrownOut is a voltage supervisory function. It

monitors the main power supply and puts the circuit in

reset state when the supply drops below a predefined

value of voltage VBO (~2.05V).

BrownOut is enabled at power up EnBrownOut=’1’

automatically. Afterwards the user can switch off the

brown out function with the bit EnBrownOut='0' in

temporarily disabled (most analog cells are switched off

during sleep). After the sleep mode the brownout function

which was selected before sleep will be reactivated.

The brown out reset occurrence is flagged with bit

ResBwnOutFlag

in register RegResStat. Write ‘0’ to

clear this flag. BrownOut reset will also set the

ResInpPAFlag bit when DisResInp bit is set ‘1’.

If the brown out voltage VBO is reached faster than the

Brown Out start-up delay time constant, then no reset

condition will flag. In case of lower speed start up both

ResBwnOutFlag and ResInpPAFlag will show. The user

may distinguish between initial ‘slow’ power-up and

‘normal’ brown out by using the bit SleepEN. This bit is

reset by POR only. In this case if after re-start the

SleepEn and ResBwnOutFlag are set, then the circuit is

coming from brown out condition. If SleepEn is reset the

circuit comes from power-up condition.

While the Brownout function is enabled the circuit will

draw additional ~6µA of IVDD current (for Bandgap and

Comparator) in all modes except sleep mode.

Figure 12. BrownOut and PowerCheck architecture

Figure 13. BO and SVLD consumption

7.5.1

BO Timings

7.5.1.1

BrownOut Startup delay ~10ms

The start-up delay allows the integrated Bandgap reference and the Comparator to stabilize after switching on the function.

The start-up delay is switched on after power-up (voltage rises above VPOR), setting EnBrownOut=’1’ or resuming from

Sleep mode. The start-up delay is independent of the current VDD voltage.

During the whole start-up delay phase no BrownOut reset will be generated.

7.5.1.2

BrownOut Filter (~30µs)

The BrownOut condition needs to be at least approx. 30µs present to initiate system reset. In case of VBAT undervoltage

not reaching the VPOR, then CPU starts to operate approx. 330µs after the VDD voltage is again above VBO (= Re-start

after BrownOut).

If the undervoltage reaches and switches on the POR function (< 1.5V), then BrownOut start-up delay as described in

7.5.1.1 applies in addition to meet the powercheck voltage VPWC before the CPU is able to operate again.

7.5.1.3

Re-start after BrownOut (~330µs)

VDD rising again above the VBO voltage will allow restart of CPU operation. However this restart is delayed by approx.

330µs (cold start delay, reset synchronization and BrownOut Filter) Refer also to Figure 12. BrownOut and PowerCheck

architecture

Note: Time constants are based on the Prescaler2 clock output that is closest to32kHz. It takes into account the prescaler

clock selection, the RC Oscillator frequency range and the RC divider settings. If running on external clock input the time

constants may change accordingly to the input frequency and clock management set-ups.

PwrCheck

BrownOut

POR

BROWN

OUT

POR

Filter

30µs

Start-Up delay

10ms

Vbat

Enable

EnBrownOut

Sleep

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