APX812-29UG-7 Diodes Inc, APX812-29UG-7 Datasheet - Page 7

• Manufacturer Part Number: APX812-29UG-7
• Description: IC SUPERVISOR 2.93V SOT143-4
• Manufacturer: Diodes Inc
• Type: Simple Reset/Power-On Resetr

Specifications of APX812-29UG-7

• Number Of Voltages Monitored: 1
• Output: Push-Pull, Totem Pole
• Reset: Active High
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 2.93V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-143, SOT-143B, TO-253AA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APX811/812
4-Pin Microprocessor Supervisor With Manual Reset
Application Information
A microprocessor’s (µP’s) reset input starts the µP in a known state. The APX811/812 asserts reset to prevent code-execution errors
during power-up, power-down, or brownout conditions. They assert a reset signal whenever the V
supply voltage declines below a
CC
MR
preset threshold or the
pin is brought low, keeping it asserted for at least 240ms after V
has risen above the reset threshold. The
CC
APX811/812 have a push-pull output stage.
The APX811/812 reset output is guaranteed to be logic low for the APX811 and high the APX812 for V
> 1V. Once V
exceeds the
CC
CC
reset threshold, an internal timer keeps
output low (and RESET high for the APX812) for the reset timeout period. After this
RESET
interval, the APX811’s
output goes high (APX812’s RESET output goes low). If a brownout condition occurs (V
dips below the
RESET
CC
reset threshold), the APX811’s
output goes low (APX812’s RESET output goes high). Any time V
goes below the reset
RESET
CC
threshold, the internal timer resets to zero, and
goes low (RESET goes high). The internal timer starts after V
returns above
RESET
CC
the reset threshold, and
remains low (RESET remains high) for the reset timeout period.
RESET
Ensuring a Valid Reset Output Down to V
= 0
CC
When V
falls below 1V, the APX811
no longer sinks current-— it becomes an open circuit. Therefore, high-impedance
RESET
CC
CMOS logic inputs connected to
can drift to undetermined voltages. This presents no problem in most applications since most
RESET
µP and other circuitry is inoperative with V
below 1V. However, in applications where
must be valid down to 0V, adding a pull
RESET
CC
down resistor to
causes any stray leakage currents to flow to ground, holding
low. R1’s value is not critical; 100k is
RESET
RESET
large enough not to load
and small enough to pull
to ground.
RESET
RESET
For the APX812 if RESET is required to remain valid for V
< 1V then a 100kΩ pull-up resistor between RESET and V
is
CC
CC
recommended.
Benefits of Highly Accurate Reset Threshold
Most µP supervisor ICs has reset threshold voltages between 5% and 10% below the value of nominal supply voltages. This ensures a
reset will not occur within 5% of the nominal supply, but will occur when the supply is 10% below nominal. When using ICs rated at only
the nominal supply ±5%, this leaves a zone of uncertainty where the supply is between 5% and 10% low, and where the reset may or may
not be asserted.
APX811/812 Rev. 2
7 of 10
OCTOBER 2009
DS31960
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Diodes Incorporated