MAX8215 Datasheet, PDF (9/12 Pages) Maxim Integrated Products – ±5V, ±12V (±15V) Dedicated Microprocessor Voltage Monitors

±5V, ±12V (±15V) Dedicated
Microprocessor Voltage Monitors
+5V
1k
2 _GND
0.1µF
8
PGND
14
V_DD
680k
680k
+V_S
3 _+5V
MAX8215
MAX8216
13
OUT1
V+
0.1µF
1k
14
VDD
13
OUT1
MAX8215
MAX8216
7 _DIN
9
DOUT
RESET
Figure 8. Alternate Bypass Scheme
1µF
Figure 7. Microprocessor Reset Circuit Monitoring Its Own
Supply Voltage
absolute maximum ratings have no effect on the refer-
ence. Within the absolute maximum ratings, the DIN
input has no effect on the reference.
Power-Supply Bypassing and Grounding
In high-noise environments where the voltage connected
to VDD may change abruptly, the reference voltage may
“bounce,” causing false comparator outputs. Eliminate
this problem using Figure 8’s RC bypass network.
Although bypassing the reference may appear to help,
Figure 8’s solution is recommended; bypassing the ref-
erence reduces its voltage change, but doing so caus-
es a time delay prior to the reference voltage returning
to its correct level.
Eliminating Output Oscillation when
Using the Auxiliary Comparator
Although hysteresis is built into the auxiliary comparator,
output oscillation problems are still possible. Oscillation
can occur when a comparator’s output couples back to
its inverting input through stray board capacitance.
Make sure the board trace leading from the comparator
output does not pass near its inverting input (or vice
versa). Also, reducing the resistance connected to DIN
reduces its susceptibility to picking up output signals. In
MAX8215
VIN
7 _DIN
MAX8216
9
DOUT
Figure 9. Alternative Means for Reducing Impedance Level
Seen at DIN
most cases, using input resistor values on the order of
100kΩ creates no problem. Since using lower resistor
values increases the supply current, another approach
is to bypass the input resistors as shown in Figure 9,
although this slows the circuit’s response. When much
larger valued input resistors are used, high valued resis-
tors on the output should be used.
When DOUT is required to sink larger currents (i.e.,
when smaller pull-up resistor values are used), oscilla-
tion problems are more likely to occur. To minimize
power consumption and to optimize stability, use the
largest value pull-up resistor feasible for the output
drive required. When lower pull-up resistor values are
used, lower values for the resistors connected to the
inputs can help alleviate oscillation problems.
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