adm12914-2arqz-rl7 Analog Devices, Inc., adm12914-2arqz-rl7 Datasheet - Page 13

• Manufacturer Part Number: adm12914-2arqz-rl7
• Description: ?0.8% Accurate Quad Uv/ov Positive/negative Voltage Supervisor
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
When a fault occurs, the UV or OV output fall time can be
expressed as
where R
approximately 50 Ω. Assuming a load capacitance of 150 pF, the
fall time is 16.5 ns.
UV / OV OUTPUT CHARACTERISTICS
Both the OV and UV outputs have strong pull-down to ground
and weak internal pull-up to V
as open-drain outputs. When the rise time on the pin is not
critical, the weak pull-up removes the requirement for an
external pull-up resistor. The open-drain configuration allows
for wire-OR’ing of outputs, which is particularly useful when
more than one signal needs to pull down on the output.
At V
V
Consequently, if the state and pull-up strength of the OV pin is
important at very low V
than 100 kΩ is advised. By adding an external pull-up resistor,
the pull-up strength on the OV pin is greater. Therefore, if it is
connected in a wire-OR’ e d configuration, the pull-down strength
of any single device must account for this additional pull-up
strength.
GLITCH IMMUNITY
The ADM12914 is immune to short transients that may occur
on the monitored voltage rails. The device contains internal
filtering circuitry that provides immunity to fast transient
glitches. Figure 9 illustrates glitch immunity performance by
showing the maximum transient duration without causing a
reset pulse. Glitch immunity makes the ADM12914 suitable for
use in noisy environments.
UNDERVOLTAGE LOCKOUT (UVLO)
The ADM12914 has an undervoltage lockout circuit that monitors
the voltage on the V
1.9 V (minimum), the circuit activates. The UV output asserts
CC
= 1 V, the weak pull-up current on OV is almost turned on.
CC
t
F
≈ 2.2( R
= 1 V, a maximum V
PULL-DOWN
PULL-DOWN
is the internal pull-down resistance, which is
CC
)( C
pin. When the voltage on V
CC
, an external pull-up resistor of no more
LOAD
OL
)
= 0.15 V at UV is guaranteed. At
CC
. This permits the pins to behave
CC
drops below
Rev. PrA | Page 13 of 16
and the OV output clears and is not allowed to assert. When
V
though an undervoltage condition had occurred on the inputs.
SHUNT REGULATOR
The ADM12914 is powered via the V
directly connected to a voltage rail of up to 6 V. In this mode,
the supply current of the device does not exceed 100 μA. An
internal shunt regulator allows the ADM12914 to operate at
higher input voltage levels by placing a shunt resistor in series
between the supply rail and the V
to less than 10 mA. Use Figure 7 in the Typical Performance
Characteristics section to assist in determining the value of
this resistance. Choose an appropriate location on the curve to
accommodate variations in V
the dropper resistor.
OV LATCH (ADM12914-1)
If an overvoltage condition occurs when the LATCH pin is
pulled low, the OV pin latches low. Pulling LATCH high clears
the latch. If an OV condition clears while LATCH is high, the
latch is bypassed and the OV pin behaves in the same fashion as
the UV pin, with an identical timeout period. If the LATCH pin
is pulled low while the timeout period is active, the OV pin
latches as before.
DISABLE (ADM12914-2)
Pulling the DIS pin high disables both the UV and OV outputs
and forces both outputs to remain weakly pulled high, regard­
less of any faults that are detected at the inputs. If a UVLO
condition is detected, the UV output is asserted and pulls low;
however, the timeout function is bypassed. As soon as the UVLO
condition clears, the UV output pulls high. To guarantee normal
operation when the pin is left unconnected, DIS has a weak 2 μA
internal pull-down current.
CC
recovers, UV exhibits the same timing characteristics as
CC
due to changes in current through
CC
pin to limit the input current
CC
pin. The V
ADM12914
CC
pin can be