sp690tep-l Exar Corporation, sp690tep-l Datasheet - Page 16

• Manufacturer Part Number: sp690tep-l
• Description: Sp690s -low Power Microprocessor Supervisory With Battery Switch-over
• Manufacturer: Exar Corporation

Figure 24. Interfacing to Microprocessors with
Bidirectional RESET I/O
Monitoring an Additional Power Supply
These P supervisors can monitor either positive
or negative supplies using a resistor voltage
divider to PFI. PFO can be used to generate an
interrupt to the P, as seen in Figure 23.
Interfacing to
Reset Pins
Any Ps with bidirectional reset pins, such as
the Motorola 68HC11 series, can interface with
the SP690_ and the SP802_ RESET outputs.
For example, if the RESET output is driven
HIGH and the
indeterminate logic levels may result. To correct
this, connect a 4.7k
RESET output and the
Figure 24. Buffer the RESET output to other
system components.
Negative-Going V
While issuing resets to the P during power-up,
power-down, and brownout conditions, these
supervisors are relatively immune to short-
duration negative-going V
(glitches). It is usually undesirable to reset the
SP690T/S/R JAN 30-06
Buffered RESET connects to System Components
P when V
GND
V
CC
RESET
CC
experiences only small glitches.
SP690T/S/R, 802/T/S/R, 804T/S/R, 805T/S/R Low Power Microprocessor Supervisory
4.7K
P wants to pull it LOW,
Ps with Bidirectional
CC
Transients
resistor between the
RESET
P reset I/O, as in
CC
transients
P
GND
V
CC
16
Figure 25 shows maximum transient duration
vs. reset-comparator overdrive, for which reset
pulses are not generated. The data was generated
using negative-going V
3.3V and ending below the reset threshold by
the magnitude indicated (reset comparator
overdrive). The graph shows the maximum pulse
width a negative-going V
typically have without causing a reset pulse to
be issued. As the amplitude of the transient
increases (i.e. goes farther below the reset
threshold), the maximum allowable pulse width
decreases. Typically, a V
100mV below the reset threshold and lasts for
40 s or less will not cause a reset pulse to be
issued. A 100nF bypass capacitor mounted close
to the V
immunity.
Figure 25. Maximum Transient Duration without
Causing a Reset Pulse vs. Reset Comparator Overdrive
CC
pin provides additional transient
Generated
RESET
NO
1nF Capacitor
V
OUT
Above Line
Generated
CC
CC
RESET
© 2006 Sipex Corporation
TO GND
pulses, starting at
CC
transient that goes
transient may