NCS199A1RSQT2G [ONSEMI]
Low- or High-Side Current Sensing;
| 型号： | NCS199A1RSQT2G |
| 厂家： | 
ONSEMI |
| 描述： | Low- or High-Side Current Sensing 光电二极管 |
| 文件： | 总15页 (文件大小：523K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
NCS199A1R, NCS199A2R,
NCS199A3R
Current-Shunt Monitors,
Voltage Output,
Bidirectional, Zero-Drift,
Low- or High-Side Current
Sensing
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The NCS199A1R, NCS199A2R, and NCS199A3R are voltage
output, current shunt monitors (also called current sense amplifiers)
which can measure voltage across shunts at common−mode voltages
from −0.3 V to 26 V, independent of supply voltage. The low offset of
the zero−drift architecture enables current sensing across the shunt
with maximum voltage drop as low as 10 mV full−scale. These
devices can operate from a single +2.2 V to +26 V power supply,
drawing a maximum of 80 mA of supply current, and are specified over
the extended operating temperature range (−40°C to +125°C).
Available in the SC70−6 package.
1
SC70−6
SQ SUFFIX
CASE 419B
MARKING DIAGRAM
6
Features
XXXMG
G
• Wide Common Mode Input Range: −0.3 V to 26 V
• Supply Voltage Range: 2.2 V to 26 V
• Low Offset Voltage: 150 mV max
• Low Offset Drift: 0.5 mV/°C max
• Low Gain Error: 1.5% max
1
XXX
M
G
= Specific Device Code
= Date Code
= Pb−Free Package
(Note: Microdot may be in either location)
• Low Gain Error Drift: 10 ppm/°C
• Rail−to−Rail Output Capability
• Low Current Consumption: 40 mA typ, 80 mA max
PIN CONNECTIONS
Typical Applications
REF
GND
Vs
OUT
IN−
• Current Sensing (High−Side/Low−Side)
• Telecom
• Power Management
• Battery Charging and Discharging
IN+
(Top View)
ORDERING INFORMATION
See detailed ordering, marking and shipping information on
page 2 of this data sheet.
© Semiconductor Components Industries, LLC, 2018
1
Publication Order Number:
March, 2018 − Rev. 1
NCS199A1R/D
NCS199A1R, NCS199A2R, NCS199A3R
RSHUNT
Supply
Load
NCS199AxR
R1
R3
IN-
-
Output
Reference
OUT
REF
IN+
+
R4
Voltage
R2
VS
+2.2 V to +26 V
0.01 uF
To
0.1 uF
ǒ Ǔ
OUT + ILOAD RSHUNT GAIN ) VREF
V
ORDERING INFORMATION
Device
†
Gain
50
R3 and R4
20 kW
R1 and R2
1 MW
Marking
Package
SC70−6
SC70−6
SC70−6
Shipping
NCS199A1RSQT2G
NCS199A2RSQT2G
NCS199A3RSQT2G
AZ3
AZ4
AZY
3000 / Tape and Reel
3000 / Tape and Reel
3000 / Tape and Reel
100
200
10 kW
1 MW
5 kW
1 MW
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
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2
NCS199A1R, NCS199A2R, NCS199A3R
Table 1. MAXIMUM RATINGS
Parameter
Symbol
Value
+30
Unit
V
Supply Voltage (Note 1)
Analog Inputs
V
S
Differential (V )−(V
)
V V
IN+, IN−
−30 to +30
(GND−0.3) to +30
V
IN+
IN−
Common−Mode (Note 2)
REF Input
V
(GND−0.3) to (V +0.3)
V
V
REF
s
Output (Note 2)
V
OUT
(GND−0.3) to (V +0.3)
s
Input Current into Any Pin (Note 2)
Maximum Junction Temperature
Storage Temperature Range
5
+150
mA
°C
°C
V
T
J(max)
T
−65 to +150
2000
STG
ESD Capability, Human Body Model (Note 3)
Charged Device Model (Note 3)
Latch−Up Current (Note 4)
HBM
CDM
2000
V
I
LU
100
mA
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
1. Refer to ELECTRICAL CHARACTERISTICS, RECOMMENDED OPERATING RANGES and/or APPLICATION INFORMATION for safe
operating parameters.
2. Input voltage at any pin may exceed the voltage shown if current at that pin is limited to 5 mA.
3. This device series incorporates ESD protection and is tested by the following methods:
ESD Human Body Model tested per JEDEC standard JS−001−2017.
ESD Charged Device Model tested per JEDEC standard JS−002−2014.
4. Latch−up Current tested per JEDEC standard JESD78E.
Table 2. RECOMMENDED OPERATING RANGES
Parameter
Common−Mode Input Voltage
Symbol
Min
−0.3
2.2
Typ
12
5
Max
26
Unit
V
V
CM
Supply Voltage
V
S
26
V
Ambient Temperature
T
A
−40
125
°C
Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses beyond
the Recommended Operating Ranges limits may affect device reliability.
Table 3. THERMAL CHARACTERISTICS (Note 5)
Parameter
Symbol
Value
Unit
Thermal Resistance, Junction−to−Air (Note 6)
SC70−6
R
250
°C/W
q
JA
5. Refer to ELECTRICAL CHARACTERISTICS, RECOMMENDED OPERATING RANGES and/or APPLICATION INFORMATION for safe
operating parameters.
2
2
6. Values based on copper area of 645 mm (or 1 in ) of 1 oz copper thickness and FR4 PCB substrate.
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3
NCS199A1R, NCS199A2R, NCS199A3R
Table 4. ELECTRICAL CHARACTERISTICS
At T = +25°C, V
= V
− V ; V = +5 V, V
= 12 V, and V
= V /2, unless otherwise noted.
A
SENSE
IN+
IN−
S
IN+
REF S
Boldface limits apply over the specified temperature range of T = −40°C to 125°C, guaranteed by characterization and/or design.
A
Symbol
INPUT
Parameter
Test Conditions
Min
Typ
Max
Unit
V
Common−Mode Input Voltage Range
Common−Mode Rejection Ratio
−0.3
26
V
CM
CMRR
V
IN+
V
= 0 V to +26 V,
SENSE
100
120
dB
= 0 mV
T = −40°C to 125°C
A
V
Offset Voltage RTI (Note 7)
RTI vs Temperature (Note 7)
V
= 0 mV
5
150
mV
OS
SENSE
dV /dT
OS
V
= 0 mV
0.1
0.5
mV/°C
SENSE
T = −40°C to +125°C
A
PSRR
RTI vs Power Supply Ratio (Note 7)
V = +2.7 V to +26 V,
0.1
10
60
mV/V
S
V
= 18 V, V
= 0 mV
IN+
SENSE
I
IB
Input Bias Current
Input Offset Current
V
V
= 0 mV
= 0 mV
39
mA
mA
SENSE
SENSE
I
IO
0.1
OUTPUT
G
Gain
NCS199A1R
NCS199A2R
NCS199A3R
50
V/V
100
200
0.2
E
G
Gain Error
V
= −5 mV to 5 mV,
+ 1.5
%
SENSE
A
T = −40°C to 125°C
Gain Error vs Temperature
Nonlinearity Error
T = −40°C to 125°C
3
10
ppm/°C
%
A
V
= −5 mV to 5 mV
0.01
1
SENSE
C
Maximum Capacitive Load
No sustained oscillation
nF
L
VOLTAGE OUTPUT
V
Swing to V Power Supply Rail
R = 10 kW to GND
A
V
−
V − 0.2
S
V
V
OH
S
L
S
T = −40°C to +125°C
0.075
V
Swing to GND
R = 10 kW to GND
V
GND
V
GND
+0.05
OL
L
T = −40°C to +125°C
+0.005
A
FREQUENCY RESPONSE
BW
Bandwidth (f
)
NCS199A1R
NCS199A2R
NCS199A3R
C
= 10 pF
LOAD
90
60
40
1
kHz
−3dB
SR
Slew Rate
V/ms
NOISE
e
Voltage Noise Density
f = 1 kHz
45
40
nV/√Hz
n
POWER SUPPLY
V
I
Operating Voltage Range
Quiescent Current
T = −40°C to +125°C
2.2
26
80
V
S
A
V
= 0 mV
mA
mA
Q
SENSE
Quiescent Current Over Temperature
7. RTI = referenced−to−input
T = −40°C to +125°C
100
A
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
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4
NCS199A1R, NCS199A2R, NCS199A3R
TYPICAL CHARACTERISTICS (T = 25°C, V = 5 V, V + = 12 V and V
= V /2 unless otherwise noted.)
S
A
S
IN
REF
(The NCS199A3R is used for Typical Characteristics)
2000
1800
1600
1400
1200
1000
800
100
80
60
40
20
0
−20
−40
−60
600
400
200
0
−80
−100
−35 −30 −25 −20−15−10 −5
0
5
10 15 20 25 30 35
−50
−40
−10
0
25
85
125 150
INPUT OFFSET VOLTAGE (mV)
TEMPERATURE (°C)
Figure 1. Input Offset Voltage Production
Distribution
Figure 2. Input Offset Voltage vs. Temperature
4500
4000
3500
3000
2500
2000
1500
1000
5
4
3
2
1
0
−1
−2
−3
500
0
−4
−5
−50
−5 −4 −3 −2
−1
0
1
2
3
4
5
−40
−10
0
25
85
125
150
COMMON−MODE REJECTION RATIO (mV/V)
TEMPERATURE (°C)
Figure 3. Common−Mode Rejection
Figure 4. Common−Mode Rejection Ratio vs.
Production Distribution
Temperature
9000
8000
7000
6000
5000
4000
3000
2000
1.0
0.8
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
1000
0
−0.8
−1.0
−1.0 −0.8 −0.6 −0.4 −0.2
0
0.2 0.4 0.6 0.8 1.0
−50
−40
−10
0
25
85
125
150
GAIN ERROR (%)
TEMPERATURE (°C)
Figure 5. Gain Error Production Distribution
Figure 6. Gain Error vs. Temperature
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5
NCS199A1R, NCS199A2R, NCS199A3R
TYPICAL CHARACTERISTICS (T = 25°C, V = 5 V, V + = 12 V and V
= V /2 unless otherwise noted.)
A
S
IN
REF
S
(The NCS199A3R is used for Typical Characteristics)
70
60
50
40
30
20
10
160
140
120
100
80
60
40
V
V
V
V
= 5 V + 250 mVpp
S
= 0 V
CM
REF
DIF
NCS199A1R
NCS199A2R
NCS199A3R
= 2.5 V
= shorted
0
20
0
C = 15 pF
L
−10
10
100
1k
10k
100k
1M
10M
1M
14
10
100
1k
10k
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 7. Gain vs. Frequency
Figure 8. Power Supply Rejection Ratio vs.
Frequency
160
140
120
100
80
V+
V(+)−0.5
V(+)−1.0
V(+)−1.5
−40°C
60
V
= 5 V
S
V(+)−2.0
V(+)−2.5
Sine Disturbance = 1 Vpp
125°C
25°C
40
V
V
= 12 V
= 2.5 V
CM
REF
20
0
C = 15 pF
L
10
100
1k
10k
100k
V(+)−3.0 0
2
4
6
8
10
12
14
FREQUENCY (Hz)
OUTPUT CURRENT (mA)
Figure 9. Common−Mode Rejection Ratio vs.
Figure 10. Positive Output Voltage Swing vs.
Output Current, VS = 2.2 V
Frequency
V+
V(+)−0.5
V(+)−1.0
V(+)−1.5
GND+3.0
GND+2.5
25°C
125°C
−40°C
GND+2.0
GND+1.5
GND+1.0
V(+)−2.0
V(+)−2.5
−40°C
GND+0.5
GND
125°C
25°C
V(+)−3.0
0
2
4
6
8
10
12
0
2
4
6
8
10 12 14
16 18 20
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
Figure 11. Negative Output Voltage Swing vs.
Output Current, VS = 2.2 V
Figure 12. Positive Output Voltage Swing vs.
Output Current, VS = 2.7 V
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NCS199A1R, NCS199A2R, NCS199A3R
TYPICAL CHARACTERISTICS (T = 25°C, V = 5 V, V + = 12 V and V
= V /2 unless otherwise noted.)
S
A
S
IN
REF
(The NCS199A3R is used for Typical Characteristics)
V+
GND+3.0
GND+2.5
25°C
125°C
−40°C
V(+)−0.5
V(+)−1.0
V(+)−1.5
V(+)−2.0
GND+2.0
GND+1.5
GND+1.0
V(+)−2.5
V(+)−3.0
GND+0.5
GND
125°C
25°C
−40°C
0
2
4
6
8
10 12 14 16 18
20
0
0
0
2
4
6
8
10 12 14 16 18 20 22 24
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
Figure 13. Negative Output Voltage Swing vs.
Output Current, VS = 2.7 V
Figure 14. Positive Output Voltage Swing vs.
Output Current, VS = 5 V
V+
V(+)−0.5
V(+)−1.0
V(+)−1.5
GND+3.0
GND+2.5
25°C
125°C
−40°C
GND+2.0
GND+1.5
GND+1.0
V(+)−2.0
V(+)−2.5
V(+)−3.0
GND+0.5
GND
125°C
25°C
−40°C
0
2
4
6
8
10 12 14 16 18 20 22 24
2
4
6
8
10 12 14 16 18 20 22 24
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
Figure 15. Negative Output Voltage Swing vs.
Output Current, VS = 5 V
Figure 16. Positive Output Voltage Swing vs.
Output Current, VS = 26 V
GND+3.0
GND+2.5
70
60
50
40
30
20
10
25°C
125°C
−40°C
I
, I , V
B+ B− REF
= 0 V
I , I , V
B+ B− REF
= 2.5 V
GND+2.0
GND+1.5
GND+1.0
GND+0.5
GND
0
−10
0
2
4
6
8
10 12 14 16 18 20 22 24
0.5
1.0
1.5
2.0
2.5
30
OUTPUT CURRENT (mA)
COMMON−MODE VOLTAGE (V)
Figure 17. Negative Output Voltage Swing vs.
Output Current, VS = 26 V
Figure 18. Input Bias Current vs.
Common−Mode Voltage with VS = 5 V
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NCS199A1R, NCS199A2R, NCS199A3R
TYPICAL CHARACTERISTICS (T = 25°C, V = 5 V, V + = 12 V and V
= V /2 unless otherwise noted.)
S
A
S
IN
REF
(The NCS199A3R is used for Typical Characteristics)
30
25
20
15
10
45
I
, I , V
= 0 V
B+ B− REF
40
35
30
25
20
15
10
I
B+
, V
REF
= 2.5 V
I , V
B− REF
= 2.5 V
5
0
5
0
−50
−5
0
5
10
15
20
25
30
−40
−10
0
25
85
125
150
COMMON−MODE VOLTAGE (V)
TEMPERATURE (°C)
Figure 19. Input Bias Current vs. Common−Mode
Figure 20. Input Bias Current vs. Temperature
Voltage with VS = 0 V (Shutdown)
100
90
80
70
60
100
50
40
30
20
10
V
V
V
=
2.5 V
= 0 V
S
NCS199A1R
NCS199A2R
NCS199A3R
REF
, V
IN− IN+
= 0 V
10
0
R = 10 kW
L
1
−50 −40
−10
0
25
85
125
150
1
10
100
1k
10k
100k
TEMPERATURE (°C)
FREQUENCY (Hz)
Figure 21. Quiescent Current vs. Temperature
Figure 22. Voltage Noise Density vs.
Frequency
1000
800
600
400
200
0
45
40
35
30
25
20
15
10
5
3.0
V
V
V
=
2.5 V
= 0 V
S
2.5
2.0
1.5
1.0
0.5
0
OUTPUT
INPUT
REF
, V
IN− IN+
= 0 V
R = 10 kW
L
−200
−400
−600
−0.5
−1.0
0
−1.5
−2.0
−800
−1000
−5
0
1
2
3
4
5
6
7
8
9
10
−0.2 −0.1
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
TIME (s)
TIME (s)
Figure 23. 0.1 Hz to 10 Hz Voltage Noise
(Referred to Input)
Figure 24. Step Response
(10 mVpp Input Step)
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NCS199A1R, NCS199A2R, NCS199A3R
TYPICAL CHARACTERISTICS (T = 25°C, V = 5 V, V + = 12 V and V
= V /2 unless otherwise noted.)
S
A
S
IN
REF
(The NCS199A3R is used for Typical Characteristics)
8
7
6
5
4
3
2
1
0
250
200
150
100
50
12
10
8
Inverting Input
INPUT
6
0
OUTPUT
4
−50
−100
−150
2
Output
0
−1
−2
−100 −50
−200
−250
−2
−200
0
50 100 150 200 250 300 350 400
0
200
400
600 800 1000 1200 1400
TIME (ms)
TIME (ms)
Figure 25. Common−Mode Voltage Transient
Figure 26. Inverting Differential Input Overload
Response
12
10
8
6
5
4
3
2
1
Supply Voltage
Noninverting Input
6
Output Voltage
4
Output
2
0
0
−2
−200
−1
0
200 400
600
800 1000 1200 1400
−200 −100 0 100 200 300 400 500 600 700 800
TIME (ms)
TIME (ms)
Figure 27. Noninverting Differential Input
Overload
Figure 28. Start−Up Response
6
Supply Voltage
5
4
3
2
Output Voltage
1
0
−200 −100 0
100 200 300 400 500 600 700 800
TIME (ms)
Figure 29. Brownout Recovery
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NCS199A1R, NCS199A2R, NCS199A3R
Basic Connections
Current Sensing Techniques
current monitoring. Figure 30 shows the NCS199AxR
circuit implementation for unidirectional operation using
high−side current sensing.
The NCS199AxR current−sense amplifiers can be
configured for both low−side and high−side current sensing.
Low−side sensing appears to have the advantage of being
straightforward, inexpensive, and can be implemented with
a simple op amp circuit. However, the NCS199AxR series
of devices provides the full differential input necessary to
get accurate shunt connections, while also providing a
built−in gain network with precision difficult to obtain with
external resistors. While at times the application requires
low−side sensing, only high−side sensing can detect a short
from the positive supply line to ground. Furthermore,
high−side sensing avoids adding resistance to the ground
path of the load being measured. The sections below focus
primarily on high−side current sensing.
Basic connections for unidirectional operation include
connecting the load power supply, connecting a current
shunt to the differential inputs of the NCS199AxR,
grounding the REF pin, and providing a power supply for the
NCS199AxR. The NCS199AxR can be connected to the
same power supply that it is monitoring current from, or it
can be connected to a separate power supply. If it is
necessary to detect short circuit current on the load power
supply, which may cause the load power supply to sag to
near zero volts, a separate power supply must be used on the
NCS199AxR. When using multiple supplies, there are no
restrictions on power supply sequencing.
When no current is flowing though the R
REF pin is connected to ground, the NCS199AxR output is
expected to be within 50 mV of ground. When current is
, and the
SHUNT
Unidirectional Operation
In unidirectional current sensing, the current always flows
in the same direction. Common applications for
unidirectional operation include power supplies and load
flowing through R
the output will swing positive, up
SHUNT,
to within 200 mV of the applied supply voltage, V .
S
RSHUNT
Supply
Load
NCS199AxR
R1
R3
IN-
IN+
-
Output
OUT
REF
+
R4
R2
VS
+2.2 V to +26 V
0.01uF
To
0.1uF
Figure 30. Basic Unidirectional Connection
Bidirectional Operation
In bidirectional current sensing, the current
measurements are taken when current is flowing in both
directions. For example, in fuel gauging, the current is
measured when the battery is being charged or discharged.
Bidirectional operation requires the output to swing both
positive and negative around a bias voltage applied to the
REF pin. The voltage applied to the REF pin depends on the
application. However, most often it is biased to either half of
the supply voltage or to half the value of the measurement
system reference. Figure 31 shows bidirectional operation
with three different circuit choices that can be connected to
the REF pin to provide a voltage reference to the
NCS199AxR.
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NCS199A1R, NCS199A2R, NCS199A3R
RSHUNT
Supply
Load
NCS199AxR
R1
R3
R4
-
IN-
Output
OUT
REF
+
IN+
Connect to any one of 3 possible circuits shown
R2
(a)
Vs
+2.2 V to +26 V
0.01uF
To
Supply
Supply
Supply
0.1uF
-
Series
Reference
+
Shunt
Reference
or zener
Op Amp
(e.g. NCS2003, NCS20071)
(b)
(c)
(d)
Figure 31. Bidirectional Current Sensing with Three Example Voltage Reference Circuits
Input and Output Filtering
The REF pin must always be connected to a low
impedance circuit, such as in the Figure 31(b), (c), and (d).
The REF pin can be connected directly to any voltage supply
or voltage reference (shunt or series). However, if a resistor
divider network is used to provide the reference voltage, a
unity gain buffer circuit must be used, as shown in
Figure 31(d).
Filtering at the input or output may be required for several
different reasons. In this section we will discuss the main
considerations with regards to these filter circuits.
In some applications, the current being measured may be
inherently noisy. In the case of a noisy signal, filtering after
the output of the current sense amplifier is often simpler,
especially where the amplifier output is fed into high
impedance circuitry. The amplifier output node provides the
greatest freedom when selecting components for the filter
and is very straightforward to implement, although it may
require subsequent buffering.
In bidirectional applications, any voltage that exceeds
V +0.3 V applied to the REF pin will forward bias an ESD
S
diode between the REF pin and the V pin. Note that this
S
exceeds the Absolute Maximum Ratings for the device.
Other applications may require filtering at the input of the
current sense amplifier. Figure 32 shows the recommended
schematic for input filtering.
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11
NCS199A1R, NCS199A2R, NCS199A3R
NCS199AxR
RFILT1
10W
RSHUNT
200mW
1nH
IN-
-
CFILT
OUT
REF
0.25mF
IN+
+
Reference
Voltage
RFILT2
10W
VS
Figure 32. Input filtering compensates for shunt inductance on shunts
less than 1 mW, as well as high frequency noise in any application
Input filtering is complicated by the fact that the added
resistance of the filter resistors and the associated resistance
mismatch between them can adversely affect gain, CMRR,
high frequency spike transient events on the current sensing
line that can overload the front end of any shunt current
sensing IC. This problem must be solved by filtering at the
input of the amplifier. Note that all current sensing IC’s are
vulnerable to this problem, regardless of manufacturer
claims. Filtering is required at the input of the device to
resolve this problem, even if the spike frequencies are above
the rated bandwidth of the device.
and V . The effect on V is partly due to input bias
OS
OS
currents as well. As a result, the value of the input resistors
should be limited to 10 W or less. Ideally, select the capacitor
to exactly match the time constant of the shunt resistor and
its inductance; alternatively, select the capacitor to provide
a pole below that point. As an example, a filtering frequency
of 100 kHz would require an 82 nF capacitor. The capacitor
can have a low voltage rating, but should have good high
frequency characteristics.
Advantages When Used for Low−Side Current Sensing
The NCS199AxR series offer many advantages for
low−side current sensing. The true differential input is ideal
for connection to either Kelvin Sensing shunts or
conventional shunts. Additionally, the true differential input
rejects the common−mode noise often present even in
low−side current sensing. The NCS199AxR also provides a
reference pin to set the output offset from an external
reference. Providing all of these features in a tiny package
makes the NCS199AxR very competitive when compared to
discrete op amp solutions.
Make the input filter time constant equal to or larger than
the shunt and its inductance time constant:
LSHUNT
RSHUNT
w 2 @ RFILT @ CFILT
This simplifies to determine the value of C
based on
FILT
using 10 W resistors for each R
:
FILT
LSHUNT
20RSHUNT
C
FILT w
Designing for Input Transients Exceeding 30 Volts
For applications that have transient common−mode
voltages greater than 30 volts, external input resistors of
10 W provide a convenient location to add either Zener
diodes or transient voltage suppression diodes (also known
as TVS diodes). There are two possible configurations: one
using a single TVS diode with diodes across the amplifier
inputs as shown in Figure 33, and the second configuration
using two TVS diodes as shown in Figure 34.
If the main purpose is to filter high frequency noise, the
capacitor should be increased to a value that provides the
desired filtering.
As the shunt resistors decrease in value, shunt inductance
can significantly affect frequency response. At values below
1 mW, the shunt inductance causes a zero in the transfer
function that often results in corner frequencies in the low
100’s of kHz. This inductance increases the amplitude of
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12
NCS199A1R, NCS199A2R, NCS199A3R
NCS199AxR
RFILT1
10W
RSHUNT
200mW
1nH
IN-
-
D1, D2
OUT
REF
1N4148
IN+
+
Reference
Voltage
RFILT2
10W
VS
TVS1
ON Semiconductor
SMBJ18(C)A
Figure 33. Single TVS transient common−mode protection
TVS1
ON Semiconductor
SMBJ18(C)A
NCS199AxR
RFILT1
10W
RSHUNT
200mW
1nH
IN-
-
OUT
REF
IN+
+
Reference
Voltage
RFILT2
10W
VS
TVS2
ON Semiconductor
SMBJ18(C)A
Figure 34. Dual TVS Transient Common−mode Protection
Selecting the Shunt Resistor
Use Zener diodes or unidirectional TVS diodes with
clamping voltage ratings up to a maximum of 30 volts.
Select TVS diodes with the lowest voltage rating possible
for use in the system. There is a wide range between standoff
voltage and maximum clamping voltage in TVS diodes.
Most diodes rated at a standoff voltage of 18 V have a
maximum clamping voltage of 29.2 V. Refer to the TVS data
sheet and the parameters of your power supply to make the
selection. In general, higher power TVS diodes demonstrate
a sharper clamping knee; providing a tighter relationship
between rated breakdown and maximum clamping voltage.
The desired accuracy of the current measurement
determines the precision, shunt size, and the resistor value.
The larger the resistor value, the more accurate the
measurement possible, but a large resistor value also results
in greater current loss.
For the most accurate measurements, use four terminal
current sense resistors, as shown in Figure 35. It provides
two terminals for the current path in the application circuit,
and a second pair for the voltage detection path of the sense
amplifier. This technique is also known as Kelvin Sensing.
This insures that the voltage measured by the sense amplifier
is the actual voltage across the resistor and does not include
the small resistance of a combined connection. When using
non−Kelvin shunts, follow manufacturer recommendations
on how to lay out the sensing traces closely.
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13
NCS199A1R, NCS199A2R, NCS199A3R
Current Output Configuration
In applications where the readout boards are remotely
located, the voltage output of the NCS199AxR can be
converted to a precision current output. The precision output
current measurements are read more accurately as it
overcomes the errors due to ground drops between the
boards.
Figure 35. Surface Mount Kelvin Shunt
Current Measurement Circuit Board
System Data Readout Board
RITOV
NCS199AxR
1kW
RIOUT
+
V = I * R
ADC
IN-
-
1kW
-
OUT
REF
+
IN+
Line Receiver
(e.g. NCS2003)
VS
Stray ground
resistance between boards
Figure 36. Remote Current Sensing
As shown in Figure 36, the R
resistor is added
overcome most ground voltage drop, stray voltages, and
noise. However, accuracy will degrade if noise or ground
drops exceed 1 V.
IOUT
between the OUT pin and the REF pin to convert the voltage
output to a current output which is taken from the REF pin
to the readout board. This circuit is intended to function with
low potentials between the boards due to ground drops or
noise. The current output is simply the relationship of the
normal output voltage of the NCS199AxR:
Shutting Down the NCS199AxR
While the NCS199AxR does not provide a shutdown pin,
a simple MOSFET, power switch, or logic gate can be used
to switch off the power to the NCS199AxR and eliminate the
quiescent current. Note that the shunt input pins will always
have a current flow via the input and feedback resistors (total
resistance of each leg always equals slightly higher than
1 MW). Also note that when powered, the shunt input pins
will exhibit the specified and well−matched typical bias
current of 39 mA. The shunt input pins support the rated
common mode voltage even when the NCS199AxR does
not have power applied.
VOUT
RIOUT
IOUT
+
A resistor value of 1 kW for R
is always a convenient
IOUT
value as it provides 1 mA/V scaling.
On the readout board, for simplicity, R
can be equal
ITOV
to R
to provide identical voltage drops across both. It is
IOUT
important to take into consideration that R
add additional voltage drops in the current measurement
path. The current source can provide enough compliance to
and R
ITOV
IOUT
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14
NCS199A1R, NCS199A2R, NCS199A3R
PACKAGE DIMENSIONS
SC−88/SC70−6/SOT−363
CASE 419B−02
ISSUE Y
2X
aaa H
D
NOTES:
D
H
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
A
3. DIMENSIONS D AND E1 DO NOT INCLUDE MOLD FLASH,
PROTRUSIONS, OR GATE BURRS. MOLD FLASH, PROTRU-
SIONS, OR GATE BURRS SHALL NOT EXCEED 0.20 PER END.
4. DIMENSIONS D AND E1 AT THE OUTERMOST EXTREMES OF
THE PLASTIC BODY AND DATUM H.
5. DATUMS A AND B ARE DETERMINED AT DATUM H.
6. DIMENSIONS b AND c APPLY TO THE FLAT SECTION OF THE
LEAD BETWEEN 0.08 AND 0.15 FROM THE TIP.
7. DIMENSION b DOES NOT INCLUDE DAMBAR PROTRUSION.
ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.08 TOTAL IN
EXCESS OF DIMENSION b AT MAXIMUM MATERIAL CONDI-
TION. THE DAMBAR CANNOT BE LOCATED ON THE LOWER
RADIUS OF THE FOOT.
D
GAGE
PLANE
6
1
5
2
4
3
L
L2
E1
E
DETAIL A
aaa
C
2X
2X 3 TIPS
bbb H
D
e
MILLIMETERS
DIM MIN NOM MAX
−−−
INCHES
MIN
−−−
NOM MAX
−−− 0.043
−−− 0.004
6X b
B
TOP VIEW
A
−−−
−−−
1.10
A1 0.00
A2 0.70
0.10 0.000
M
ddd
C A-B D
0.90
0.20
0.15
2.00
2.10
1.25
0.65 BSC
0.36
1.00 0.027 0.035 0.039
0.25 0.006 0.008 0.010
0.22 0.003 0.006 0.009
2.20 0.070 0.078 0.086
2.20 0.078 0.082 0.086
1.35 0.045 0.049 0.053
0.026 BSC
b
C
D
E
0.15
0.08
1.80
2.00
A2
DETAIL A
A
E1 1.15
e
L
0.26
0.46 0.010 0.014 0.018
0.006 BSC
L2
0.15 BSC
0.15
aaa
bbb
ccc
ddd
0.006
0.012
0.004
0.004
0.30
0.10
0.10
6X
ccc C
A1
SEATING
PLANE
c
C
SIDE VIEW
END VIEW
RECOMMENDED
SOLDERING FOOTPRINT*
6X
0.30
6X
0.66
2.50
0.65
PITCH
DIMENSIONS: MILLIMETERS
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
ON Semiconductor and
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