EVAL-ADM2914EBZ Analog Devices Inc, EVAL-ADM2914EBZ Datasheet - Page 12

• Manufacturer Part Number: EVAL-ADM2914EBZ
• Description: Voltage Supervisor Eval. Board
• Manufacturer: Analog Devices Inc

Specifications of EVAL-ADM2914EBZ

• Silicon Manufacturer: Analog Devices
• Application Sub Type: Voltage Supervisor
• Kit Application Type: Power Management
• Silicon Core Number: ADM2914
• Main Purpose: Power Management, Power Supply Supervisor/Tracker/Sequencer
• Embedded: No
• Utilized Ic / Part: ADM2914
• Primary Attributes: Voltage Detector & Supervisor
• Secondary Attributes: Open-Drain Output
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADM2914
UV AND OV RISE AND FALL TIMES
The UV and OV output rise times (from 10% to 90%) can be
approximated using the following formula:
where:
R
imate value of 400 kΩ at room temperature with V
C
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 a strong pull-down to
ground and a weak internal pull-up to V
to behave 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 are
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 ADM2914 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 ADM2914 suitable for
use in noisy environments.
PULL-UP
LOAD
CC
= 1 V, the weak pull-up current on OV is almost turned on.
CC
t
t
is the external load capacitance on the output pin.
R
F
= 1 V, a maximum V
is the internal weak pull-up resistance with an approx-
≈
≈
PULL-DOWN
2
2
( 2 .
( 2 .
R
R
PULL
PULL
is the internal pull-down resistance, which is
−
−
UP
DOWN
)(
CC
C
, an external pull-up resistor of no more
)(
LOAD
C
OL
LOAD
= 0.15 V at UV is guaranteed. At
)
)
CC
. This permits the pins
CC
> 1 V.
Rev. B | Page 12 of 16
UNDERVOLTAGE LOCKOUT (UVLO)
The ADM2914 has an undervoltage lockout circuit that monitors
the voltage on the V
below 1.9 V (minimum), the circuit is activated. The UV output
is asserted and the OV output is cleared and not allowed to
assert. When V
characteristics as if an undervoltage condition had occurred
on the inputs.
SHUNT REGULATOR
The ADM2914 is powered via the V
be 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 ADM2914 to
operate at voltage levels greater than 6 V by simply placing a
dropper resistor in series between the supply rail and the V
pin to limit the input current to less than 10 mA.
Once the supply voltage, V
appropriate value for the dropper resistor can be calculated.
Begin by determining the maximum supply current
required, I
reference and/or the pull resistors between the outputs and
the V
minimum and maximum shunt regulator voltage specified
in Table 1, V
following calculations.
Calculate the maximum and minimum dropper resistor
values
Based on these values, choose a real-world resistor value
within this range. Then, given the specified accuracy of this
resistor, calculate the minimum and maximum real resistor
value variation, R
The maximum device power is calculated as follows:
To check that the calculated value of the resistor will be
acceptable, calculate the maximum device temperature rise;
Add this value to the ambient operating temperature. If the
resistor value is acceptable, the result will lie within the
specified operating temperature range of the device,
to +85°C.
Temp
R
P
R
CC
DeviceMax
MIN
MAX
pin to the maximum specified supply current. The
V
=
RISEmax
CCtotal
SHUNTmax
=
V
SHUNT min
V
IN
=
CC
IN
, by adding the current drawn from the
V
max
min
recovers, UV exhibits the same timing
SHUNTmax
=
REALmin
100
I
θ
−
CC
I
CCtotal
JA
−
V
CCtotal
and V
pin. When the voltage on V
V
P
SHUNT
μ
DeviceMax
SHUNT
and R
⎡
⎢
⎣
(
V
IN
SHUNT max
min
IN
, has been established, an
max
REALmax
max
R
REAL
−
, are also required in the
V
CC
, respectively.
SHUNTmax
min
pin. The V
)
−
CC
Icc
CC
drops
TOTAL
pin can
−40°C
⎤
⎥
⎦
+
CC