EVAL-ADM2914EBZ Analog Devices Inc, EVAL-ADM2914EBZ Datasheet - Page 10

• 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
THRESHOLD ACCURACY
The reset threshold accuracy is fundamental, especially at lower
voltage levels. Consider an FPGA application that requires a 1 V
core voltage input with tolerance of ±5%, where the supply has a
specified regulation, for example, ±1.5%. As shown in Figure 19, to
ensure that the supply is within the FPGA input voltage require-
ment range, its voltage level must be monitored for UV and OV
conditions. The voltage swing on the supply itself causes the
voltage band available for setting the monitoring threshold to be
quite narrow. In this example, the threshold voltages, including
the tolerances, must fit within a monitor region of only 0.035 V.
The ADM2914 device with 0.1% resistors can achieve this level
of accuracy.
VOLTAGE MONITORING EXAMPLE
To illustrate how the ADM2914 device works in a real application,
consider the 1 V input example shown in Figure 19, with the
addition of a −12 V rail.
The first step is to choose the nominal current flow through
both voltage divider circuits, for example, 5 μA.
For the 1 V ± 5% input, due to the specified ±1.5% regulation of
the supply, the UV and OV thresholds should be set in the middle
of the voltage monitoring band. In this case, on the ±3.25%
points of the supply, the UV threshold is 0.9675 V and the OV
threshold is 1.0325 V.
Input these values into Equation 1.
Insert the value of R
Then substitute the calculated values for R
Equation 3.
This design approach meets the application specifications. As
described previously, the 1 V rail is specified with an input
requirement of ±5% and a supply tolerance of ±1.5%. This
effectively means that the OV threshold of the monitoring
VOLTAGE
VOLTAGE
1V CORE
1.015V
0.985V
1.05V
0.95V
R
R
R
UV
Z
Y
X
=
=
=
Figure 19. Monitoring Threshold Accuracy Example
(
(
5
. 1
. 0
×
+5% TOLERANCE
–5% TOLERANCE
0325
9675
10
1
0 (
0 (
−
6
) 5 .
) 5 .
)
)
(
(
−
5
5
Z
( )
( )
96
1
×
1
×
into Equation 2.
10
10
5 .
−
−
kΩ
6
6
)
)
−
≈
−
96
96
. 6
3.5% RANGE FOR
OV MONITORING
+1.5% SUPPLY REGULATION
–1.5% SUPPLY
REGULATION
3.5% RANGE FOR
UV MONITORING
42
5 .
5 .
kΩ
kΩ
kΩ
≈
≈
. 6
96
Z
42
and R
5 .
kΩ
kΩ
Y
into
TIME
t
UOTO
Rev. B | Page 10 of 16
device, including all the tolerance factors, must fit within the
1.015 V to 1.05 V range. Similarly, the UV threshold range must
be between 0.95 V and 0.985 V.
The four worst-case scenarios of minimum and maximum
undervoltage and overvoltage thresholds are calculated as follows:
Minimum overvoltage threshold
Maximum overvoltage threshold
The maximum and minimum overvoltage threshold values lie
within the 1.015 V to 1.05 V range specified. The minimum and
maximum undervoltage thresholds are calculated as follows:
Minimum undervoltage threshold
Maximum undervoltage threshold
Again, these values fit within the specified undervoltage
monitoring range. All four worst-case scenarios satisfy the
tolerance requirement; therefore, the design approach is valid.
V
V
V
V
=
=
=
=
=
OV
OV
UV
UV
. 1
. 1
. 0
. 0
. 0
Figure 20. Positive and Negative Supply Monitor Example
016
049
4925
953
984
_
_
_
_
96.5kΩ
96.5kΩ
–12V RAIL
1V RAIL
MIN
MAX
MIN
MAX
6.42Ω
V
V
V
V
⎛
⎜ ⎜
⎝
=
=
1
=
=
>
<
>
<
+
0 (
0 (
0 (
0 (
. 1
. 1
. 0
. 0
(
2.49MΩ
5 .
5 .
23.4kΩ
89.8kΩ
015
05
5 .
96
5 .
95
985
V
V
V
V
,
(
V
500
V
96
−
V
−
+
V
+
1
1
,
1
1
500
+
5 .
5 .
5 .
5 .
6420
%)
%)
%)
%)
)(
VH1
VL1
VL3
VH3
REF
⎛
⎜
⎜
⎝
⎛
⎜
⎜
⎝
. 1
⎛
⎜
⎜
⎝
⎛
⎜
⎜
⎝
1
1
1
1
)(
001
+
+
+
+
ADM2914
. 0
(
(
(
(
R
R
)
999
R
R
GND
Y
V
X
Y
X
5V
CC
+
−
)
−
+
⎞
⎟ ⎟
⎠
0
0
0
0
(
(
(
1 .
1 .
R
1 .
(
R
R
1 .
R
%
%)
X
%
Z
X
%)
SEL
Z
OV
UV
) (
−
+
) (
+
−
+
+
+
+
0
0
0
0
(
1 .
1 .
(
R
1 .
R
1 .
R
R
%)
Z
%
%)
Z
Y
%
Y
+
)
−
−
)
+
0
0
0
0
1 .
1 .
1 .
1 .
%
%
%)
%)
)
)
⎞
⎟
⎟
⎠
⎞
⎟
⎟
⎠
⎞
⎟
⎟
⎠
⎞
⎟
⎟
⎠