RSTn

TCAL

WAKE

DONE

INT. OSC.

PGOOD

A

B

C

D

TPL5000

SNAS628B – JULY 2013 – REVISED DECEMBER 2014

www.ti.com

Feature Description (continued)

The frame, D, shows a typical PGOOD, high to low transition. As soon as PGOOD is low, the internal oscillator is

powered OFF and the digital output pins, TCAL, RSTn, and WAKE, are asynchronously reset by the falling edge

of the PGOOD signal, such that TCAL and WAKE reset at low logical values, while RSTn resets at a high logical

value.

Figure 7. Timing PGOOD, WAKE, RSTN, TCAL

8.3.1.3 Watchdog Feature

Most of the microcontroller-based systems need to be self-reliant; if the software hangs for any reason, the

microcontroller must be reset. The TPL5000 can provide this functionality by connecting a microcontroller

programmable output pin to the DONE input pin. If the DONE line does not toggle within the selected delay

period, then the microcontroller is not operating properly and must be reset.

The TPL5000 recognizes a valid DONE signal as a low to high transition; if two DONE signals are received

within the delay period the second signal is ignored.

In the TPL5000, the watchdog window and the delay period are equivalent. A valid "DONE" signal resets the

watchdog counter only, and not the delay time counter. A PGOOD low to high transition clears both the

watchdog and delay time counters.

Figure 6 shows the watchdog feature of the TPL5000. The sequence A, B, C is a standard sequence with the

microcontroller working properly. In this normal sequence, the microcontroller sends a valid "DONE" (arrow B)

before the end of the delay period. The sequence C, D ,E is an anomalous sequence in which the microcontroller

is not in a valid state, and it does not send the DONE signal (dashed pulse) before the end of the delay period.

The TPL5000 determines the microcontroller is hung and sends a RESET signal (arrow E) when the period delay

has elapsed.

8.3.1.4 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 microcontroller.

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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