ADM6318CZ28ARJ-RL7 Analog Devices Inc, ADM6318CZ28ARJ-RL7 Datasheet - Page 11

• Manufacturer Part Number: ADM6318CZ28ARJ-RL7
• Description: IC SUPERVISOR WATCHDOG SOT23-5
• Manufacturer: Analog Devices Inc
• Type: Simple Reset/Power-On Resetr

Specifications of ADM6318CZ28ARJ-RL7

• Package / Case: SOT-23-5, SC-74A, SOT-25
• Mounting Type: Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Output: Push-Pull, Push-Pull
• Reset: Active High/Active Low
• Number Of Voltages Monitored: 1
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 2.8V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATION INFORMATION
WATCHDOG INPUT CURRENT
In order to minimize watchdog input current (and minimize
overall power consumption), leave WDI low for the majority
of the watchdog timeout period. When driven high, WDI can
draw as much as 160 µA. Pulsing WDI low-high-low at a low
duty cycle reduces the effect of the large input current. When
WDI is unconnected, a window comparator disconnects the
watchdog timer from the reset output circuitry so that reset is
not asserted when the watchdog timer times out.
NEGATIVE-GOING V
To avoid unnecessary resets caused by fast power supply
transients, the ADM6316/ADM6317/ADM6318/ADM6319/
ADM6320/ADM6321/ADM6322 are equipped with glitch
rejection circuitry. The typical performance characteristic in
Figure 13 plots V
magnitude. The curves show combinations of transient
magnitude and duration for which a reset is not generated for
4.63 V and 2.93 V reset threshold parts. For example, with the
2.93 V threshold, a transient that goes 100 mV below the
threshold and lasts 8 µs typically does not cause a reset, but if
the transient is any bigger in magnitude or duration, a reset is
generated. An optional 0.1 µF bypass capacitor mounted close
to V
ENSURING RESET VALID TO V
Both active-low and active-high reset outputs are guaranteed to
be valid for V
resistor with push-pull configured reset outputs, valid outputs
for V
output, a resistor connected between RESET and ground pulls
the output low when it is unable to sink current. For the active-
high case, a resistor connected between RESET and V
the output high when it is unable to source current. A large
resistance such as 100 kΩ should be used so that it does not
overload the reset output when V
ADM6316/
ADM6318/
ADM6319
CC
CC
V
provides additional glitch rejection.
CC
as low as 0 V are possible. For an active-low reset
CC
Figure 18. Ensuring Reset Valid to V
as low as 1 V. However, by using an external
RESET
CC
transient duration vs. the transient
100kΩ
CC
TRANSIENTS
CC
ADM6317/
ADM6318/
ADM6319/
ADM6321/
ADM6322
is above 1 V.
ADM6316/ADM6317/ADM6318/ADM6319/ADM6320/ADM6321/ADM6322
CC
V
CC
= 0 V
CC
= 0 V
RESET
CC
100kΩ
pulls
Rev. 0 | Page 11 of 12
WATCHDOG SOFTWARE CONSIDERATIONS
In implementing the microprocessor’s watchdog strobe code,
quickly switching WDI low-high and then high-low (minimizing
WDI high time) is desirable for current consumption reasons.
However, a more effective way of using the watchdog function
can be considered.
A low-high-low WDI pulse within a given subroutine prevents
the watchdog timing out. However, if the subroutine becomes
stuck in an infinite loop, the watchdog cannot detect this because
the subroutine continues to toggle WDI. A more effective coding
scheme for detecting this error involves using a slightly longer
watchdog timeout. In the program that calls the subroutine,
WDI is set high. The subroutine sets WDI low when it is called.
If the program executes without error, WDI is toggled high and
low with every loop of the program. If the subroutine enters an
infinite loop, WDI is kept low, the watchdog times out, and the
microprocessor is reset.
SUBROUTINE
PROGRAM
SET WDI
SET WDI
RETURN
START
CODE
MR
HIGH
LOW
ADM6316
Figure 20. Typical Application Circuit
Figure 19. Watchdog Flow Diagram
V
CC
RESET
WDI
RESET
I/O
INFINITE LOOP:
WATCHDOG
TIMES OUT
µP
RESET