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參數資料
| 型號： | AD22001 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 圓形連接器 |
| 英文描述： | Circular Connector; MIL SPEC:MIL-DTL-38999 Series I; Body Material:Metal; Series:LJT; No. of Contacts:4; Connector Shell Size:21; Connecting Termination:Crimp; Circular Shell Style:Wall Mount Receptacle; Body Style:Straight RoHS Compliant: No |
| 中文描述： | 5通道單片比較監(jiān)測燈 |
| 文件頁數： | 5/8頁 |
| 文件大?。?/td> | 146K |
| 代理商： | AD22001 |
AD22001
REV. A
–5–
T hreshold Biasing
T he comparators are all activated by a common bias connection
which controls their threshold voltage. T he threshold is
compensated for variations in temperature and operating
voltage. T he temperature compensation is approximately +3770
ppm/
°
C. T his causes the threshold to track the voltage across a
copper shunt operated at constant current and varying
temperature. T he comparators are intended for use with small
value shunts made using normal copper tracks on PC cards.
GND
FUSE CHECK
OUT 5
POWER
OUT
LAMP
LAMP
FUSE
FUSE
OUT
(3
×
4)
OUT
3 & 4
FUSE
FUSE
CHIP ENABLE
LAMP
LAMP
LAMP
OUT 1 & 2
FUSE
CHECK
AD22001
1
2
3
4
5
6
7
8
9
10
NOTE
R
ARE COPPER-TRACK SHUNT RESISTORS ON THE
PRINTED CIRCUIT BOARD.
11
20
19
18
17
16
15
14
12
13
+V
S
R
S
R
S
+V
BATT
R
S
R
S
R
S
Figure 4. Application Suggestion
T he power supply voltage compensation alters the comparator
threshold with a 50% sensitivity around the nominal 13.5 V
powering voltage. T hat is, a 10% change in battery voltage
results in a 5% change in threshold voltage. T his compensation
approximately tracks the current in a hot lamp which typically
varies nonlinearly with applied voltage, with approximately 50%
sensitivity.
ON-OFF and Power Control
T he AD22001 is intended to be powered directly from the
battery voltage. In normal operation an internal switch connects
internal circuits and the Power Out pin to the battery voltage,
under control of the Chip Enable. When Chip Enable is high
(above 9 V) the switch is on, the AD22001 is active and the
Power Out pin will be close to battery potential. When Chip
Enable is low, or open circuit, the switch will open and the
AD22001 will be inactive and Power Out will go low.
In order to protect the external circuits connected to Power Out
from overvoltage, the power switch is “soft” and limits the
output voltage to typically 16 V. If the applied voltage exceeds
this value, both Power Out and the internal voltage (from which
the threshold is derived) will limit. T he limited Power Out
voltage will be available for moderate overvoltage conditions
such as double battery. If the applied voltage goes above
typically 33 V, the internal switch will be turned off, the lamp
monitor circuits will be inactivated and Power Out will go low
for the duration of the overvoltage.
Copper Resistors
Low value resistors can be produced as part of the printed
circuit pattern on copper clad boards. T hese resistors will have a
large positive T C, but this effect is compensated by the
temperature sensitive threshold in the AD22001.
At a design temperature of 24
°
C the sheet resistance,
ρ
S
, of 35
μ
m
copper cladding is about 0.5 milliOhms per square (m
/sq),
and 70
μ
m copper is about 0.25 m
/sq. T hat is, a resistor made
from 35
μ
m copper with an aspect ratio (length/width) of 1 will
have a resistance of 0.5 m
, while with an aspect ratio of 4 its
resistance would be 2 m
, etc. T he resistor can be designed for
a given value R by noting R =
ρ
S
L/W, so that L = RW/
ρ
S
.
T he sheet resistance
ρ
S
is based on the thickness of copper
cladding (with 1 ounce per square foot (oz./ft
2
) copper at
0.0014" approx. equal to 35
μ
m, and 2 oz./ft
2
copper at 0.0028"
approx. equal to 70
μ
m) and the temperature. Choosing the
resistance value to correspond to the desired current trip level
and AD22001 threshold at 22
°
C, the 24
°
C “round number” is
convenient allowing a 2
°
C gradient from the resistor to the IC.
Choose W, the track width, as the larger of two values to be
determined. First the conductor should be sized so that the
nominal operating current results in only a small temperature
rise. T his can be determined from the table from MIL ST D-
275C, 9 Jan. 1970 (Figure 8).
Second, the width must be great enough to survive the peak
currents which are allowed by the fuse which supplies the track.
T his can be determined from recommendations by the laminate
manufacturer, or the MIL table.
Using the larger of the two values determined for W, the length
of the resistor can be calculated. T he resistor is defined by
“K elvin” connections to the ends which sense the voltage across
this section of the track, and apply it to the differential input of
the AD22001 comparator.
As an example, consider the case of a parking lamp which
nominally draws 325 mA, and is on a circuit fused for 10A.
Suppose the board uses 70
μ
m (2 oz.) copper cladding, then a
conductor width of a few mils will suffice for the nominal
current. However, the 10A fuse may allow as much as 13.5A
current before it opens. A conductor 0.1" in width will carry
13.5A with less than 50
°
C rise in temperature, according to the
table.
Selecting 1/2 the nominal current as the AD22001 trip level
gives:
R = 1.75 mV/(325 mA/2)
or R = 10.769 m
.
Substituting these values in the expression for L,
L = 10.769 m
3
0.1" /0.25 m
per sq
or L = 4.3".
A track of at least 0.1" in width should be used to convey this
current anywhere on the board. A section 4.3" long should be
sampled by K elvin connections to the comparator differential
inputs.
T his case, where the peak current available is large while the
sensed current is small, results in extremes of resistor length. In
such cases it may be convenient to bend or fold the shunt
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相關代理商/技術參數 |
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| AD22001-2 | 制造商:Analog Devices 功能描述: |
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| AD22001P | 制造商:Analog Devices 功能描述: |
| AD22002 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
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