+3V Voltage Monitoring, Low-Cost µP

Supervisory Circuits

6

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Pin Description

PIN

MAX706P

MAX706AP

MAX706R/S/T,

MAX706AR/AS/AT

MAX708R/S/T

SO/DIP

µMAX

SO/DIP

µMAX

SO/DIP µMAX

NAME

FUNCTION

13

1

3

1

3

MR

Active-Low, Manual-Reset Input. Pull MR below 0.6V to trigger a

be shorted to GND with a switch. MR is internally connected to a

24

2

4

2

4

Supply Voltage Input

35

3

5

3

5

GND

Ground

46

4

6

4

6

PFI

Adjustable Power-Fail Comparator Input. Connect PFI to a

resistive divider to set the desired PFI threshold. When PFI is

less than 1.25V, PFO goes low and sinks current; otherwise,

PFO remains high. Connect PFI to GND if not used.

57

5

7

5

7

PFO

Active-Low, Power-Fail Comparator Output. PFO asserts when

PFI is below the internal 1.25V threshold. PFO deasserts when

PFI is above the internal 1.25V threshold. Leave PFO

unconnected if not used.

68

6

8

—

—

WDI

Watchdog Input. A falling or rising transition must occur at

WDI within 1.6s to prevent WDO from asserting (see Figure 4).

The internal watchdog timer is reset to zero when reset is

asserted or when transition occurs at WDI. The watchdog

function for the MAX706P/R/S/T can not be disabled. The

watchdog timer for the MAX706AP/AR/AS/AT disables when

WDI input is left open or connected to a tri-state output in its

high-impedance state with a leakage current of less than

600nA.

71

—

—

8

2

RESET

below the reset threshold or MR is held low. It remains low for

200ms after the reset conditions end (Figure 3).

82

8

2

—

—

WDO

Active-Low Watchdog Output. WDO goes low when a

transition does not occur at WDI within 1.6s and remains low

until a transition occurs at WDI (indicating the watchdog

falls below the reset threshold; however, unlike the reset

the reset threshold.

——

7

1

7

1

RESET

below the reset threshold or MR is held low. It remains low for

200ms after the reset conditions end (Figure 3).

——

—

—

6

8

N.C.

No Connection. Not internally connected.