Datasheet

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
C
OSC
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
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