MAX6344_UT-T View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX6344_UT-T Datasheet PDF : 8 Pages
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6-Pin µP Reset Circuit with
Power-Fail Comparator
VCC
V+
R1
VCC
RESET
(RESET)
PFI
MAX6342
MAX6343
MR
MAX6344
R2
PFO
GND
TO µP
BUFFERED RESET TO
OTHER SYSTEM
COMPONENTS
VCC
MAX6342
MAX6345
RESET
4.7kΩ
VCC
µP
RESET
( ) ARE FOR MAX6344 ONLY.
Figure 7. Monitoring Two Supplies
VCC
R1
VCC
100kΩ
MR
MAX6342
PFI
MAX6343
MAX6344
PFO
100kΩ
R2
V-
GND
( ) ARE FOR MAX6344 ONLY.
RESET
(RESET)
VCC - 1.25V = 1.25V - VTRIP
R1
R2
VTRIP < 0
Figure 8. Monitoring a Negative Voltage
Note that this method does not work with the open-drain
output of the MAX6343. The resistor value used is not
critical, but it must be large enough not to load the reset
output when VCC is above the reset threshold. For most
applications, 100kΩ is adequate.
Monitoring Two Supplies
Monitor another voltage by connecting a resistor-divider
to PFI as shown in Figure 7. The threshold voltage will
then be given by:
VTH(PFI) = 1.25[(R1 + R2) / R2]
where VTH(PFI) is the threshold at which the monitored
voltage will trip PFO.
A good rule of thumb for selecting the resistors is to
choose R2 between 250kΩ and 500kΩ and solve for R1.
Connect PFO to MR in applications that require reset to
assert when the second voltage falls below its threshold.
GND
GND
Figure 9. Interfacing to µPs with Bidirectional Reset I/O
Monitoring a Negative Voltage
Connect the circuit as shown in Figure 8 to use the
power-fail comparator to monitor a negative supply rail.
PFO stays low when V- is good. When V- rises to cause
PFI to be above +1.25V, PFO goes high. By adding the
resistors and transistor as shown, a high PFO triggers
reset. As long as PFO remains high, the MAX6342/
MAX6343/MAX6344 will keep reset asserted. Note that
the accuracy of this circuit depends on the PFI thresh-
old tolerance, the VCC line voltage, and the resistors.
Also, ensure that the voltage at PFI remains above
GND.
Interfacing to µPs with
Bidirectional Reset Pins
SOT Top Marks
PART
MAX6342LUT-T
MAX6342MUT-T
MAX6342TUT-T
MAX6342SUT-T
MAX6342RUT-T
MAX6342ZUT-T
MAX6343LUT-T
MAX6343MUT-T
MAX6343TUT-T
MAX6343SUT-T
MAX6343RUT-T
MAX6343ZUT-T
SOT TOP
MARK
AACP
AACQ
AACR
AACS
AACT
AACU
AACV
AACW
AACX
AACY
AACZ
AADA
PART
MAX6344LUT-T
MAX6344MUT-T
MAX6344TUT-T
MAX6344SUT-T
MAX6344RUT-T
MAX6344ZUT-T
MAX6345LUT-T
MAX6345MUT-T
MAX6345TUT-T
MAX6345SUT-T
MAX6345RUT-T
MAX6345ZUT-T
SOT TOP
MARK
AADQ
AADR
AADS
AADT
AADU
AADV
AADW
AADX
AADY
AADZ
AAEA
AAEB
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