MAX6303CSA+T Maxim Integrated Products, MAX6303CSA+T Datasheet - Page 10

• Manufacturer Part Number: MAX6303CSA+T
• Description: IC SUPERVISOR MPU 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Simple Reset/Power-On Resetr

Specifications of MAX6303CSA+T

• Number Of Voltages Monitored: 1
• Output: Push-Pull, Totem Pole
• Reset: Active Low
• Reset Timeout: 2.8 ms Minimum
• Voltage - Threshold: Adjustable/Selectable
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Undervoltage Threshold: Adjustable
• Overvoltage Threshold: Adjustable
• Output Type: Active Low, Push-Pull
• Manual Reset: Resettable
• Watchdog: Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 5.2 ms
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 1 V
• Supply Current (typ): 4 uA
• Maximum Power Dissipation: 471 mW
• Maximum Operating Temperature: + 70 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: 0 C
• Power Fail Detection: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

In those applications where RESET must be valid down
to 0V, adding a pulldown resistor between RESET and
ground sinks any stray leakage currents, holding
RESET low (Figure 9). The value of the pulldown resistor
is not critical; 100kΩ is large enough not to load RESET
and small enough to pull RESET to ground. For applica-
tions using the MAX6304, a 100kΩ pullup resistor
between RESET and V
V
To help the watchdog timer monitor software execution
more closely, set and reset the watchdog input at differ-
ent points in the program, rather than pulsing the
watchdog input high-low-high or low-high-low. This
technique avoids a stuck loop in which the watchdog
timer would continue to be reset within the loop, keeping
the watchdog from timing out.
Figure 11 shows an example of a flow diagram where
the I/O driving the watchdog input is set high at the
beginning of the program, set low at the beginning of
every subroutine or loop, then set high again when the
program returns to the beginning. If the program should
hang in any subroutine the problem would quickly be
corrected, since the I/O is continually set low and the
watchdog timer is allowed to time out, causing a reset
or interrupt to be issued. When using extended mode,
as described in the Watchdog Input Current section,
this scheme does result in higher average WDI input
current than does the method of leaving WDI low for the
majority of the timeout period and periodically pulsing it
low-high-low.
SRT and SWT are precision current sources. When
developing the layout for the application, be careful to
minimize board capacitance and leakage currents
around these pins. Traces connected to these pins
+5V, Low-Power µP Supervisory Circuits
with Adjustable Reset/Watchdog
Figure 9. Ensuring RESET Valid to V
10
CC
falls below 1V (Figure 10).
______________________________________________________________________________________
Watchdog-Software Considerations
Layout Considerations
MAX6303
GND
CC
RESET
V
CC
will hold RESET high when
CC
V
CC
= 0V
100kΩ
0.1µF
should be kept as short as possible. Traces carrying
high-speed digital signals and traces with large voltage
potentials should be routed as far from these pins as
possible. Leakage currents and stray capacitance
(e.g., a scope probe) at these pins could cause errors
in the reset and/or watchdog timeout period. When
evaluating these parts, use clean prototype boards to
ensure accurate reset and watchdog timeout periods.
RESET IN is a high-impedance input that is typically
driven by a high-impedance resistor-divider network
(e.g., 1MΩ to 10MΩ). Minimize coupling to transient sig-
nals by keeping the connections to this input short. Any
DC leakage current at RESET IN (e.g., a scope probe)
causes errors in the programmed reset threshold. Note
that sensitive pins are located on the GND side of the
device, away from the digital I/O, to simplify board layout.
Figure 10. Ensuring RESET Valid to V
Figure 11. Watchdog Flow Diagram
MAX6304
GND
SUBROUTINE OR
PROGRAM LOOP
SET WDI HIGH
RESET
SET WDI
RETURN
START
V
LOW
END
CC
CC
V
0.1µF
CC
= 0V
100kΩ