adm12914-2arqz-rl7 Analog Devices, Inc., adm12914-2arqz-rl7 Datasheet - Page 11

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

Preliminary Technical Data
tolerances, must fit within a monitor region of just 0.024 V. The
ADM12914 device with 0.1% resistors can achieve this level of
accuracy.
VOLTAGE MONITORING EXAMPLE
To illustrate how the ADM12914 device works in a real-world
application, consider the 1 V input example shown in Figure 19,
with the addition of a −5 V ± 10% negative voltage monitoring
requirement.
The first step is to choose the current flow through both voltage
divider circuits, for example, 5 μA.
For the 1 V ± 5% input, due to the specified ±2.6% regulation of
the supply, the UV and OV threshold should be set in the middle
of the undervoltage and overvoltage monitoring bands, respec­
tively. In this case, on the ±3.8% points of the supply, which are
0.962 V for the UV threshold and 1.038 V for OV threshold.
Input these values into Equation 1 to Equation 3 as follows:
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 ±2.8%. This
effectively means the OV threshold of the monitoring device,
including all the tolerance factors, must fit within the 1.026 V
to 1.05 V range. Similarly, the UV threshold range must be
between 0.95 V and 0.974 V.
The four worst-case scenarios of minimum and maximum
undervoltage and overvoltage thresholds are calculated as follows:
VOLTAGE
VOLTAGE
1V CORE
1.026V
0.974V
1.05V
0.95V
R
R
R
Y
UV
Z
X
=
=
=
(0.962)(5
(1.038)(5 ×10
5
×
10
1
Figure 19. Monitoring Accuracy Example
(0.5)(1)
(0.5)(1)
−
6
−
Z
×
2.4% RANGE FOR OV MONITORING
+2.6% SUPPLY REGULATION
–2.6% SUPPLY REGULATION
2.4% RANGE FOR UV MONITORING
96.5 kΩ
into Equation 2.
10
−6
−
6
)
)
−
≈ 96.5 kΩ
96.5kΩ ≈
−
7.59 kΩ
7.41 kΩ
≈
96.5 kΩ
Z
and R
Y
t
UOTO
into
TIME
Rev. PrA | Page 11 of 16
(1)
(2)
(3)
Minimum overvoltage threshold
Maximum overvoltage threshold
The maximum and minimum overvoltage threshold values
reside within the 1.026 V to 1.05 V range specified.
The minimum and maximum undervoltage thresholds are
calculated as follows:
Minimum undervoltage threshold
Maximum undervoltage threshold
These values fit within the specified undervoltage monitoring
range. All four worst-case scenarios satisfy the tolerance
requirement; therefore, the design approach is valid.
Next, consider a −5 V input, which is specified with a ±12%
input. The threshold accuracy required by the supply is chosen
to be within ±5% of the −5 V rail. The UV and OV threshold
should be set in the middle of the undervoltage and overvoltage
monitoring bands, respectively. In this case, on the ±8.5%
V
UV _ MIN
=1.029 V > 1.026 V
= 1.0477 V < 1.05 V
= 0.9557 V > 0.95 V
= 0.9729 V < 0.974 V
V
V
V
= 0.496 ⎜ ⎜1 +
OV _ MIN
OV _ MAX
UV _ MAX
Figure 20. Positive and Negative Supply Monitor Example
96.5kΩ
7.41kΩ
96.5kΩ
= (0.5 V − 0.8%) ⎜ ⎜ 1 +
–5V RAIL
1V RAIL
⎛
⎝
= (0.5V − 0.8%) ⎜ ⎜ 1 +
= (0.5V + 0.8%) ⎜ ⎜ 1 +
= (0.5 V + 0.8%) ⎜ ⎜ 1 +
(96,500 + 7410)(0.999) ⎞
1.09MΩ
14.3kΩ
93.1kΩ
(96,500)(1.001)
⎛
⎝
VH1
VL1
VL3
VH3
REF
(R
⎛
⎝
⎛
⎝
⎛
⎝
Y
ADM12914
+ 0.1%) + (R
(R
(R
(R − 0.1%) + (R − 0.1%)
GND
(R
V
X
X
Y
5V
CC
− 0.1%) + (R
+ 0.1%) + (R
X
⎟ ⎟
⎠
− 0.1%)
(R + 0.1%)
(R − 0.1%)
(R + 0.1%)
Z
Z
SEL
X
OV
UV
Z
ADM12914
+ 0.1%)
Y
Y
Z
+ 0.1%) ⎞
− 0.1%) ⎞
⎞
⎟
⎟
⎠
⎟
⎟
⎠
⎟
⎟
⎠
⎞
⎟
⎟
⎠