RSTn

TCAL

WAKE

DONE

TIMER

PGOOD

t

TPL5000

SNAS628A – JULY 2013 – REVISED JULY 2013

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Figure 5 shows the supervisor feature of the TPL5000. The sequence F, G is a standard sequence where the µC

is in deep sleep and a voltage supply drop occurs (which is highlighted by the PGOOD high to low transition).

When PGOOD is high again, a reset pulse at the end of the delay period is sent to the µC (arrow F), then the µC

executes its routine (memory has been reloaded upon reset) and sends the "DONE" signal.

Figure 5. Watchdog and Supervisor Feature

Calibration Pulse

The TPL5000 is based on a ultra-low power oscillator which has a relatively low frequency and low accuracy;

however, it shows very good cycle to cycle repeatability and very low temperature drift. In most of the

applications, the accuracy of the oscillator is enough, but if a more accurate measure of the delay period is

required, it is possible to measure the base period of the internal oscillator. A single pulse, which has the same

duration as the base period of the internal oscillator, is present at the TCAL pin of the TPL5000. This pulse starts

after a half period of the internal oscillator from either the falling edge of the RESET pulse, or the rising edge of

the WAKE pulse.

A µC connected to the TPL5000 can routinely measure the width of the TCAL pulse using a counter and an

external crystal. Once the base period of the TPL5000 is measured, the actual time delay is calculated by

multiplying the measured period by a factor, N (see Table 2), dependent on the nominal selected time delay.

The resolution and the accuracy of the measurement depend on the external crystal. Since the frequency of the

internal oscillator of the TPL5000 is very stable, the measurement of the calibration pulse is suggested only when

a high gradient of ambient temperature is observed. The measurement of the TCAL pulse is useful in battery-

powered applications that implement a precise battery life counter in the µC.

Different Utilizations of the TPL5000

When either the watchdog or the supervisor feature of the TPL5000 are not required, it is possible to disable

them reducing the interconnections between the TPL5000 and the µC.

Connecting the DONE pin either to GND or to TCAL pin disables the watchdog feature. If connected to GND, the

TPL5000 only sends a reset pulse when the time delay elapses. If DONE is connected to TCAL, the TPL5000

sends out just one RESET pulse after a PGOOD low to high transition, when the time delay elapses and then

WAKE pulses when the successive time delay elapses.

Connecting the PGOOD pin to the supply pin of the TPL5000 disables the supervisor feature.

10

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