The NCS21871, NCS21872 and NCS21874 family of zero−drift op
amps feature offset voltage as low as 45 mV over the 1.8 V to 5.5 V
supply voltage range. The zero−drift architecture reduces the offset
drift to as low as 0.4 mV/°C and enables high precision measurements
over both time and temperature. This family has low power
consumption over a wide dynamic range and is available in space
saving packages. These features make it well suited for signal
conditioning circuits in portable, industrial, automotive, medical and
consumer markets.
www.onsemi.com
5
1
SOT23−5
SN SUFFIX
CASE 483
5
1
SC70−5
SQ SUFFIX
CASE 419A
Features
• Gain−Bandwidth Product: 270 kHz to 350 kHz
• Low Supply Current: 17 mA (typ at 3.3 V)
• Low Offset Voltage: 45 mV max
• Low Offset Drift: 0.4 mV/°C max
• Wide Supply Range: 1.8 V to 5.5 V
• Wide Temperature Range: −40°C to +125°C
• Rail−to−Rail Input and Output
• Available in Single, Dual and Quad Packages
• NCV Prefix for Automotive and Other Applications Requiring
Unique Site and Control Change Requirements; AEC−Q100
Qualified and PPAP Capable
Applications
• Automotive
• Battery Powered/ Portable Application
• Sensor Signal Conditioning
• Low Voltage Current Sensing
• Filter Circuits
• Bridge Circuits
• Medical Instrumentation
1
UDFN8
MU SUFFIX
CASE 517AW
8
1
SOIC−8
D SUFFIX
CASE 751
14
1
TSSOP−14 WB
DT SUFFIX
CASE 948G
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page 2 of this data sheet.
ORDERING INFORMATION
See detailed ordering and shipping information on page 3 of
this data sheet.
Over operating free−air temperature, unless otherwise stated.
ParameterRatingUnit
Supply Voltage6V
INPUT AND OUTPUT PINS
Input Voltage (Note 1)
Input Current (Note 1)±10 mA
Output Short Circuit Current(Note 2)Continuous
TEMPERATURE
Operating Temperature Range
Storage Temperature Range−65 to +150°C
Junction Temperature +150°C
ESDRATINGS (Note 3)
Human Body Model (HBM)
Charged Device Model (CDM)±2000 V
OTHER RATINGS
Latch−up Current (Note 4)
MSLLevel 1
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. Input terminals are diode−clamped to the power−supply rails. Input signals that can swing more than 0.3 V beyond the supply rails should
be current limited to 10 mA or less
2. Short−circuit to ground.
3. This device series incorporates ESD protection and is tested by the following methods:
ESD Human Body Model tested per JEDEC standard JS−001 (AEC−Q100−002)
ESD Charged Device Model tested per JEDEC standard JESD22−C101 (AEC−Q100−011)
4. Latch−up Current tested per JEDEC standard: JESD78.
(VSS) − 0.3 to (VDD) + 0.3 V
−40 to +125°C
±4000 V
100mA
THERMAL INFORMATION (Note 5)
Parameter
Thermal Resistance,
Junction to Ambient
5. As mounted on an 80x80x1.5 mm FR4 PCB with 650 mm2 and 2 oz (0.07 mm) thick copper heat spreader. Following JEDEC JESD/EIA 51.1,
51.2, 51.3 test guidelines
SymbolPackageValueUnit
q
JA
SOT23−5 / TSOP5290
SC70−5 / SC−88−5 / SOT−353−5290
ECP5157
Micro8 / MSOP8298
SOIC−8250
UDFN8228
SOIC−14216
TSSOP−14155
°C/W
RECOMMENDED OPERATING CONDITIONS
ParameterSymbolRangeUnit
Supply Voltage (VDD − VSS)V
Specified Operating Temperature RangeT
Input Common Mode Voltage RangeV
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.
= +25°C, RL = 10 kW connected to midsupply, VCM = V
At T
A
Boldface limits apply over the specified operating temperature range, guaranteed by characterization and/or design.
= 1.8 V to 5.5 V
S
= midsupply, unless otherwise noted.
OUT
ParameterUnitMaxTypMinConditionsSymbol
POWER SUPPLY
Power Supply Rejection Ratio
PSRR
TA = +25°C106130
dB
Full temperature range98
Turn−on Timet
Quiescent Current
(Note 8)
ON
I
Q
VS = 5 V100
1.8 V ≤ VS ≤ 3.3 V
3.3 V < VS ≤ 5.5 V
ms
2040mA
40
2845
45
6. Guaranteed by characterization and/or design
7. Specified over the full common mode range: V
8. No load, per channel
− 0.1 < VCM < VDD + 0.1
SS
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.
The NCS21871, NCS21872, and NCS21874 precision op
amps provide low offset voltage and zero drift over
temperature. The input common mode voltage range
extends 100 mV beyond the supply rails to allow for sensing
near ground or VDD. These features make the NCS21871
series well−suited for applications where precision is
required, such as current sensing and interfacing with
sensors.
IN+
IN−
+
−
The NCS21871 series of precision op amps uses a
chopper−stabilized architecture, which provides the
advantage of minimizing offset voltage drift over
temperature and time. The simplified block diagram is
shown in Figure 19. Unlike the classical chopper
architecture, the chopper stabilized architecture has two
signal paths.
Main amp
+
−
−
+
+
−
Chopper
Figure 19. Simplified NCS21871 Block Diagram
In Figure 19, the lower signal path is where the chopper
samples the input offset voltage, which is then used to
correct the offset at the output. The offset correction occurs
at a frequency of 125 kHz. The chopper−stabilized
architecture is optimized for best performance at
frequencies up to the related Nyquist frequency (1/2 of the
offset correction frequency). As the signal frequency
exceeds the Nyquist frequency, 62.5 kHz, aliasing may
occur at the output. This is an inherent limitation of all
chopper and chopper−stabilized architectures.
Nevertheless, the NCS21871 op amps have minimal
aliasing up to 125 kHz and low aliasing up to 190 kHz when
compared to competitor parts from other manufacturers.
ON Semiconductor’s patented approach utilizes two
RC notch filterChopper
RC notch filter
cascaded, symmetrical, RC notch filters tuned to the
chopper frequency and its fifth harmonic to reduce aliasing
effects.
The chopper−stabilized architecture also benefits from
the feed−forward path, which is shown as the upper signal
path of the block diagram in Figure 19. This is the high speed
signal path that extends the gain bandwidth up to 350 kHz.
Not only does this help retain high frequency components of
the input signal, but it also improves the loop gain at low
frequencies. This is especially useful for low−side current
sensing and sensor interface applications where the signal is
low frequency and the differential voltage is relatively
small.
Low−side current sensing is used to monitor the current
through a load. This method can be used to detect
over−current conditions and is often used in feedback
control, as shown in Figure 20. A sense resistor is placed in
series with the load to ground. Typically, the value of the
R
V
LOAD
Load
R
1
3
VDD
+
R
SENSE
−
R
2
R
4
Figure 20. Low−Side Current Sensing
sense resistor is less than 100 mW to reduce power loss
across the resistor. The op amp amplifies the voltage drop
across the sense resistor with a gain set by external resistors
R1, R2, R3, and R4 (where R1 = R2, R3 = R4). Precision
resistors are required for high accuracy, and the gain is set
to utilize the full scale of the ADC for the highest resolution.
VDD
VDD
Microcontroller
ADC
control
Differential Amplifier for Bridged Circuits
Sensors to measure strain, pressure, and temperature are
often configured in a Wheatstone bridge circuit as shown in
Figure 21. In the measurement, the voltage change that is
VDD
Figure 21. Bridge Circuit Amplification
EMI Susceptibility and Input Filtering
Op amps have varying amounts of EMI susceptibility.
Semiconductor junctions can pick up and rectify EMI
signals, creating an EMI−induced voltage offset at the
output, adding another component to the total error. Input
pins are the most sensitive to EMI. The NCS21871 op amp
family integrates low−pass filters to decrease sensitivity to
EMI.
produced is relatively small and needs to be amplified before
going into an ADC. Precision amplifiers are recommended
in these types of applications due to their high gain, low
noise, and low offset voltage.
VDD
−
+
General Layout Guidelines
To ensure optimum device performance, it is important to
follow good PCB design practices. Place 0.1 mF decoupling
capacitors as close as possible to the supply pins. Keep traces
short, utilize a ground plane, choose surface−mount
components, and place components as close as possible to
the device pins. These techniques will reduce susceptibility
to electromagnetic interference (EMI). Thermoelectric
effects can create an additional temperature dependent
offset voltage at the input pins. To reduce these effects, use
metals with low thermoelectric−coefficients and prevent
temperature gradients from heat sources or cooling fans.
The UDFN8 package has an exposed leadframe die pad on
the underside of the package. This pad should be soldered to
the PCB, as shown in the recommended soldering footprint
in the Package Dimensions section of this datasheet. The
center pad can be electrically connected to VSS or it may be
left floating. When connected to VSS, the center pad acts as
a heat sink, improving the thermal resistance of the part.
1. DIMENSIONING AND TOLERANCING PER ASME
Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. MAXIMUM LEAD THICKNESS INCLUDES LEAD FINISH
THICKNESS. MINIMUM LEAD THICKNESS IS THE
MINIMUM THICKNESS OF BASE MATERIAL.
4. DIMENSIONS A AND B DO NOT INCLUDE MOLD
FLASH, PROTRUSIONS, OR GATE BURRS. MOLD
FLASH, PROTRUSIONS, OR GATE BURRS SHALL NOT
EXCEED 0.15 PER SIDE. DIMENSION A.
5. OPTIONAL CONSTRUCTION: AN ADDITIONAL
TRIMMED LEAD IS ALLOWED IN THIS LOCATION.
TRIMMED LEAD NOT TO EXTEND MORE THAN 0.2
FROM BODY.
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION A AND B DO NOT INCLUDE
MOLD PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)
PER SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 (0.005) TOTAL
IN EXCESS OF THE D DIMENSION AT
MAXIMUM MATERIAL CONDITION.
6. 751−01 THRU 751−06 ARE OBSOLETE. NEW
STANDARD IS 751−07.
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION A DOES NOT INCLUDE MOLD
FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH OR GATE BURRS SHALL NOT
EXCEED 0.15 (0.006) PER SIDE.
4. DIMENSION B DOES NOT INCLUDE
INTERLEAD FLASH OR PROTRUSION.
INTERLEAD FLASH OR PROTRUSION SHALL
NOT EXCEED 0.25 (0.010) PER SIDE.
5. DIMENSION K DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.08 (0.003) TOTAL
IN EXCESS OF THE K DIMENSION AT
MAXIMUM MATERIAL CONDITION.
6. TERMINAL NUMBERS ARE SHOWN FOR
REFERENCE ONLY.
7. DIMENSION A AND B ARE TO BE
DETERMINED AT DATUM PLANE −W−.
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