Note 1: The MAX690/MAX692/MAX694 watchdog timeout period is fixed at 1.6s nominal, the MAX690/692 reset pulse width is fixed

at 50ms nominal and the MAX694 is 200ms nominal.

Note 2: When the MAX691 OSC SEL pin is low, OSC IN can be driven by an external clock signal or an external capacitor can be

connected between OSC IN and GND. The nominal internal oscillator frequency is 6.55kHz. The nominal oscillator frequency

with capacitor is:

OSC

120,000

f

(Hz)

C(pF)

=

Note 3: See Electrical Characteristics table for minimum and maximum timing values.

Figure 8. Oscillator Circuits

Table 1. MAX691/MAX693/MAX695 Reset Pulse Width and Watchdog Timeout Selections

OSC SEL

OSC IN

WATCHDOG TIMEOUT PERIOD

RESET TIMEOUT PERIOD

NORMAL

IMMEDIATELY

AFTER REST

MAX691/MAX693

MAX695

Low

External Clock Input

1024 clks

4096 clks

512 clks

2048 clks

Low

External Capacitor

400ms/47pF x C

1.6s/47pF x C

200ms/47pF x C

800ms/47pF x C

Floating

Low

100ms

1.6s

50ms

200ms

Floating

Floating

1.6s

1.6s

50ms

200ms

MAX691

MAX693

MAX695

EXTERNAL CLOCK

0 TO 250kHz

OSC SEL

OSC IN

8

7

MAX691

MAX693

MAX695

EXTERNAL OSCILLATOR

OSC SEL

OSC IN

8

7

MAX691

MAX693

MAX695

INTERNAL OSCILLATOR

1.6s WATCHDOG

N.C.

OSC SEL

OSC IN

8

N.C.

8

7

MAX691

MAX693

MAX695

INTERNAL OSCILLATOR

100ms WATCHDOG

OSC SEL

OSC IN

7

N.C.

MAX690–MAX695

Microprocessor Supervisory Circuits

www.maximintegrated.com

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