RS8557,RS8558,RS8559
Zero-Drift, Rail-to-Rail I/O CMOS Operational
Amplifiers
FEATURES
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DESCRIPTION
The RS8557, RS8558, RS8559 series of CMOS
operational amplifiers use auto-zero techniques to
simultaneously provide very low offset voltage (20μV
max) and near-zero drift over time and temperature.
This family of amplifiers has ultralow noise, offset and
power.
Low Offset Voltage: 3uV
Input Offset Drift: 0.03μV/°C
High Gain Bandwidth Product: 4.3MHz
Rail-to-Rail Input and Output
High Gain, CMRR, PSRR:120dB
High Slew Rate: 2.5V/μs
Low Noise: 0.93uVp-p (0.01~10Hz)
Low Power Consumption: 650μA /op amp
Overload Recovery Time:1us
Low Supply Voltage: +2.7 V to +5.5 V
No External Capacitors Required
Extended Temperature: -40°C to +125°C
This miniature, high-precision operational amplifiers
offset high input impedance and rail-to-rail input and
rail-to-rail output swing. With high gain-bandwidth
product of 4.3MHz and slew rate of 2.5V/μs.
Single or dual supplies as low as +2.7V (±1.35V) and
up to +5.5V (±2.75V) may be used.
APPLICATIONS
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The RS8557/RS8558/RS8559 are specified for the
extended industrial and automotive temperature
range (-40°C to 125°C). The RS8557 single amplifier
is available in 5-lead SOT23, 8-lead MSOP8 and 8lead SOIC packages, The RS8558 dual amplifier is
available in 8-lead SOIC and 8-lead MSOP narrow
surface mount packages, The RS8559 quad amplifier
is available in 14-lead SOIC and 14-lead narrow
TSSOP packages.
Temperature Sensors
Medical/Industrial Instrumentation
Pressure Sensors
Battery-Powered Instrumentation
Active Filtering
Weight Scale Sensor
Strain Gage Amplifiers
Power Converter/Inverter
Device Information (1)
PART NUMBER
RS8557
RS8558
RS8559
PACKAGE
SOT23-5
SOIC-8(SOP8)
MSOP-8
SOIC-8(SOP8)
MSOP-8
SOIC-14(SOP14)
TSSOP-14
BODY SIZE(NOM)
2.90mm×1.60mm
4.90mm×3.90mm
3.00mm×3.00mm
4.90mm×3.90mm
3.00mm×3.00mm
8.65mm×3.90mm
5.00mm×4.40mm
(1) For all available packages, see the orderable addendum at the end of the data sheet.
REV B.3
1
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RS8557,RS8558,RS8559
Pin Configuration and Functions (Top View)
RS8557
RS8557
V-
2
+IN
3
5
+
-
NC
1
-IN
2
+IN
3
V-
4
V+
4
+
1
-
OUT
8
NC
7
V+
6 OUT
-IN
SOT23-5
5
NC
SOIC-8(SOP8),MSOP-8
Pin Description
PIN
NAME
-IN
+IN
NC
OUT
VV+
RS8557
SOT23-5
4
3
1
2
5
RS8557
SOIC-8(SOP8)/MSOP8
2
3
1,5,8
6
4
7
I/O
DESCRIPTION
I
I
O
-
Negative (inverting) input
Positive (noninverting) input
No internal connection (can be left floating)
Output
Negative (lowest) power supply
Positive (highest) power supply
RS8558
OUT A
1
-IN A
2
+IN A
3
V-
+
A
B+
4
8
V+
7
OUTB
6
-IN B
5
+IN B
SOIC-8(SOP8),MSOP-8
Pin Description
NAME
-INA
+INA
-INB
+INB
OUTA
OUTB
VV+
PIN
SOIC-8(SOP8)/MSOP8
2
3
6
5
1
7
4
8
I/O
DESCRIPTION
I
I
I
I
O
O
-
Inverting input, channel A
Noninverting input, channel A
Inverting input, channel B
Noninverting input, channel B
Output, channel A
Output, channel B
Negative (lowest) power supply
Positive (highest) power supply
2
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Pin Configuration and Functions (Top View)
RS8559
OUT A
1
-IN A
2
+IN A
14
OUT D
13
-IN D
3
12
+IN D
V+
4
11
V-
+IN B
5
10
+IN C
-IN B
6
9
-IN C
OUT B
7
8
OUT C
A
- +
- +
B
D
+ -
+ C
SOIC-14(SOP14),TSSOP-14
Pin Description
NAME
-INA
+INA
-INB
+INB
-INC
+INC
-IND
+IND
OUTA
OUTB
OUTC
OUTD
VV+
PIN
SOIC-14(SOP14)/TSSOP-14
2
3
6
5
9
10
13
12
1
7
8
14
11
4
I/O
DESCRIPTION
I
I
I
I
I
I
I
I
O
O
O
O
-
Inverting input, channel A
Noninverting input, channel A
Inverting input, channel B
Noninverting input, channel B
Inverting input, channel C
Noninverting input, channel C
Inverting input, channel D
Noninverting input, channel D
Output, channel A
Output, channel B
Output, channel C
Output, channel D
Negative (lowest) power supply
Positive (highest) power supply
3
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SPECIFICATIONS
Absolute Maximum Ratings
Over operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
7
(V-)-0.5
(V+) +0.5
(V-)-0.5
(V+) +0.5
-10
10
-55
55
Continuous
-40
125
150
-65
150
Supply, Vs=(V+) - (V-)
Signal input pin (2)
Signal output pin (3)
Signal input pin (2)
Signal output pin (3)
Output short-circuit (4)
Operating range, TA
Junction, TJ
Storage, Tstg
Voltage
Current
Temperature
UNIT
V
mA
mA
°C
(1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device
reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those specified is not implied.
(2) Input terminals are diode-clamped to the power-supply rails. Input signals that can swing more than 0.5V beyond the supply rails should be currentlimited to 10mA or less.
(3) Output terminals are diode-clamped to the power-supply rails. Output signals that can swing more than 0.5V beyond the supply rails should be currentlimited to ±55mA or less.
(4) Short-circuit to ground, one amplifier per package.
ESD Ratings
V(ESD)
Electrostatic discharge
Human-body model (HBM)
Machine Model (MM)
VALUE
UNIT
5000
400
V
Recommended Operating Conditions
Over operating free-air temperature range (unless otherwise noted)
Supply voltage，Vs= (V+) - (V-）
MIN
2.7
±1.35
-40
Single-supply
Dual-supply
Specified temperature
NOM
MAX
5.5
±2.75
125
UNIT
V
°C
Thermal Information:RS8557
RS8557
THERMAL METRIC (1)
5PINS
SOT23-5
273.8
SOIC-8
116
8PINS
MSOP-8
165
UNIT
°C/W
RϴJA
Junction-to-ambient thermal resistance
RϴJC(top)
Junction-to-case(top) thermal resistance
126.8
60
53
°C/W
RϴJB
Junction-to-board thermal resistance
85.9
56
87
°C/W
ѰJT
ѰJB
Junction-to-top characterization parameter
Junction-to-board characterization parameter
Junction-to-case(bottom) thermal resistance
10.9
84.9
12.8
98.3
4.9
85
°C/W
°C/W
N/A
N/A
N/A
°C/W
RϴJC(bot)
4
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Thermal Information:RS8558
RS8558
8PINS
THERMAL METRIC (1)
UNIT
SOIC-8
116
MSOP8
165
°C/W
RϴJC(top)
Junction-to-case(top) thermal resistance
60
53
°C/W
RϴJB
Junction-to-board thermal resistance
56
87
°C/W
ѰJT
ѰJB
Junction-to-top characterization parameter
Junction-to-board characterization parameter
Junction-to-case(bottom) thermal resistance
12.8
98.3
4.9
85
°C/W
°C/W
N/A
N/A
°C/W
RϴJA
Junction-to-ambient thermal resistance
RϴJC(bot)
Thermal Information:RS8559
RS8559
14PINS
THERMAL METRIC (1)
UNIT
SOIC-14
83.8
TSSOP-14
120.8
°C/W
RϴJA
Junction-to-ambient thermal resistance
RϴJC(top)
Junction-to-case(top) thermal resistance
70.7
34.3
°C/W
RϴJB
Junction-to-board thermal resistance
59.5
62.8
°C/W
ѰJT
ѰJB
Junction-to-top characterization parameter
Junction-to-board characterization parameter
Junction-to-case(bottom) thermal resistance
11.6
37.7
1
56.5
°C/W
°C/W
N/A
N/A
°C/W
RϴJC(bot)
5
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PACKAGE/ORDERING INFORMATION
Orderable
Device
Package Type
Pin
Channel
Op Temp(°C)
Device Marking
Package Qty
RS8557XF
SOT23-5
5
1
-40℃~125℃
8557
Tape and Reel,3000
RS8557XK
SOIC-8(SOP8)
8
1
-40℃~125℃
RS8557
Tape and Reel,2500
RS8557XM
MSOP-8
8
1
-40℃~125℃
RS8557
Tape and Reel,3000
RS8558XK
SOIC-8(SOP8)
8
2
-40℃~125℃
RS8558
Tape and Reel,2500
RS8558XM
MSOP-8
8
2
-40℃~125℃
RS8558
Tape and Reel,3000
RS8559XP
SOIC-14(SOP14)
14
4
-40℃~125℃
RS8559
Tape and Reel,2500
RS8559XQ
TSSOP-14
14
4
-40℃~125℃
RS8559
Tape and Reel,3000
6
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ELECTRICAL CHARACTERISTICS
Boldface limits apply over the specified temperature range, TA = –40°C to +125°C.
(At TA = +250C, Vs=5V, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted.)
PARAMETER
RS8557, RS8558, RS8559
CONDITION
MIN
TYP
UNIT
MAX
OFFSET VOLTAGE
Input Offset Voltage
VS Temperature
VS Power Supply
Vos
VCM = Vs/2
dVos/dT
PSRR
VS = +2.7V to +5.5V, VCM = 0
105
Channel Separation, dc
3
20
μV
0.03
0.2
μV/0C
120
dB
0.13
μV/V
50
pA
10
pA
INPUT BIAS CURRENT
Input Bias Current
IB
Input Offset Current
Ios
VCM = Vs/2
NOISE PERFORMANCE
Input Voltage Noise
Input Voltage Noise
enp-p
f=0.01Hz to 10Hz
0.93
enp-p
f=0.01Hz to 1Hz
0.32
μVpp
μVpp
Input Voltage Noise Density
en
f=1KHz
45
nV/√Hz
Input Current Noise Density
in
f=10Hz
2.3
fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
VCM
(V-)-0.2
Common-Mode Rejection Ratio CMRR
(V–) – 0.2V < VCM < (V+)+ 0.2V
105
(V+)+0.2
V
120
dB
Differential
1
pF
Common-Mode
5
pF
120
dB
INPUT CAPACITANCE
OPEN-LOOP GAIN
Open-Loop Voltage Gain
AOL
RL=10KΩ, VO=0.3V to 4.7V, -40°C~125°C
SR
G=+1
105
DYNAMIC PERFORMANCE
Slew Rate
Gain-Bandwidth Product
GBW
Overload Recovery Time
2.5
V/μs
4.3
MHz
1
us
V
OUTPUT CHARACTERISTICS
Output Voltage High
VOH
Output Voltage Low
VOL
Short-Circuit Current
ISC
RL=100 KΩ to GND
4.99
4.998
RL=10 KΩ to GND
4.95
4.98
V
RL=100 KΩ to V+
1
10
mV
RL=10 KΩ to V+
10
30
mV
48
mA
POWER SUOOLY
Operating Voltage Range
Quiescent Current/ Amplifier
2.7
IQ
650
7
5.5
V
900
uA
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TYPICAL CHARACTERISTICS
At TA = +25C, Vs=5V, RL = 10kΩ connected to VS/2, VOUT = VS/2, unless otherwise noted.
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
Population
Number Of Amplifiers
6
OFFSET VOLTAGE DRIFT PRODUCTION
DISTRIBUTION
5
4
3
2
1
0
-20 -15 -10
-5
0
5
10
15
20
-30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30
Offset Voltage (uV)
Input Offset Drift (nV/℃)
OPEN−LOOP GAIN AND PHASE vs FREQUENCY
Open-Loop Gain(dB)
120
Phase
100
130
110
90
80
70
60
50
40
30
20
Input Bias Current(pA)
Gain
Phase Margin (°)
140
INPUT BIAS CURRENT vs TEMPERATURE
10K
100
10
0
-20
10
1K
10
-10
10M
100K
Frequency(Hz)
-40 -20
0
20
40
60
80 100 120 140
Temperature(℃)
POWER−SUPPLY REJECTION RATIO vs
FREQUENCY
140
140
120
COMMON−MODE REJECTION RATIO vs
FREQUENCY
120
100
100
CMRR(dB)
PSRR(dB)
1K
80
60
40
80
60
40
20
20
0
100
1K
10K
100K
1M
0
10M
100
Frequency(Hz)
8
1K
10K
100K
Frequency(Hz)
1M
10M
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TYPICAL CHARACTERISTICS
At TA = +25C, Vs=5V, RL = 10kΩ connected to VS/2, VOUT = VS/2, unless otherwise noted.
QUIESCENT CURRENT vs TEMPERATURE
QUIESCENT CURRENT vs TEMPERATURE
660
650
Quiescent Current(uA)
Quiescent Current(uA)
660
640
630
620
610
650
640
630
620
610
600
-40 -20 0
-40 -20 0 20 40 60 80 100 120 140
Temperature(℃) Vs=2.7V
20 40 60 80 100 120 140
Temperature(℃) Vs=5V
SINK CURRENT vs TEMPERATURE
65
65
Sink Current(mA)
70
60
55
50
60
55
50
45
45
40
40
-40 -20 0
-40 -20 0 20 40 60 80 100 120 140
Temperature(℃)
20 40 60 80 100 120 140
Temperature(℃)
LARGE−SIGNAL STEP RESPONSE
SMALL−SIGNAL STEP RESPONSE
CL=100PF
CL=100PF
1V/div
50mV/div
Source Current(mA)
SOURCE CURRENT vs TEMPERATURE
70
200ns/div
1us/div
9
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RS8557,RS8558,RS8559
TYPICAL CHARACTERISTICS
At TA = +25C, Vs=5V, RL = 10kΩ connected to VS/2, VOUT = VS/2, unless otherwise noted.
VIN
0V
0V
VS=±2.5V
G=-100
VS=±2.5V
G=-100
VOUT
200ns/DIV
200ns/DIV
400nV/div
0.01Hz TO 10Hz NOISE AT Vs=2.7V
200nV/div
0.01Hz TO 10Hz NOISE AT Vs=5V
10s/div
10s/div
0.01Hz TO 1Hz NOISE AT Vs=5V
0.01Hz TO 1Hz NOISE AT Vs=2.7V
200nV/div
100nV/div
0V
1V/div
VOUT
200mV/div
VIN
1V/div
0V
NEGATIVE OVERVOLTAGE RECOVERY
200mV/div
POSITIVE OVERVOLTAGE RECOVERY
10s/div
10s/div
10
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RS8557,RS8558,RS8559
Detailed Description
Overview
The RS8557, RS8558, RS8559 series op amps are unity-gain stable and free from unexpected output phase
reversal. They use auto-zeroing techniques to provide low offset voltage and very low drift over time and
temperature.
Good layout practice mandates use of a 0.1µF capacitor placed closely across the supply pins.
For lowest offset voltage and precision performance, circuit layout and mechanical conditions should be
optimized. Avoid temperature gradients that create thermoelectric (Seebeck) effects in thermocouple junctions
formed from connecting dissimilar conductors. These thermally-generated potentials can be made to cancel by
assuring that they are equal on both input terminals.
• Use low thermoelectric-coefficient connections (avoid dissimilar metals).
• Thermally isolate components from power supplies or other heat-sources.
• Shield op amp and input circuitry from air currents, such as cooling fans.
Following these guidelines will reduce the likelihood of junctions being at different temperatures, which can
cause thermoelectric voltages of 0.1µV/°C or higher, depending on materials used.
OPERATING VOLTAGE
The RS8557, RS8558, RS8559 series op amps operate over a power-supply range of +2.7V to +5.5V (±1.35V
to ±2.75V). Supply voltages higher than 7V (absolute maximum) can permanently damage the amplifier.
Parameters that vary over supply voltage or temperature are shown in the Typical Characteristics section of
this data sheet.
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APPLICATION NOTE
Typical Applications
Bidirectional Current-Sensing
This single-supply, low-side, bidirectional current-sensing solution detects load currents from –1 A to 1 A. The
single-ended output spans from 110 mV to 3.19 V. This design uses the RS8557, RS8558, RS8559 because
of its low offset voltage and rail-to-rail input and output. One of the amplifiers is configured as a difference
amplifier and the other provides the reference voltage.
VCC
VCC
VREF
R5
+
U1B
R6
ILOAD
VBUS
+
R2
R1
+
VSHUNT
+
RSHUNT
VOU T
U1A
R3
VCC
RL
R4
Figure 4. Bidirectional Current-Sensing Schematic
Design Requirements
This solution has the following requirements:
• Supply voltage: 3.3 V
• Input: –1 A to 1 A
• Output: 1.65 V ±1.54 V (110 mV to 3.19 V)
Detailed Design Procedure
The load current, ILOAD, flows through the shunt resistor (RSHUNT) to develop the shunt voltage, VSHUNT. The shunt
voltage is then amplified by the difference amplifier, which consists of U1A and R1 through R4. The gain of the
difference amplifier is set by the ratio of R4 to R3. To minimize errors, set R2 = R4 and R1 = R3. The reference
voltage, VREF, is supplied by buffering a resistor divider using U1B. The transfer function is given by Equation 1.
VOUT=VSHUNT×Gain Diff_Amp +VREF
Where
VSHUNT=ILOAD×RSHUNT
Gain Diff_Am p =
R4
R3
(1)
There are two types of errors in this design: offset and gain. Gain errors are introduced by the tolerance of the
shunt resistor and the ratios of R4 to R3 and, similarly, R2 to R1. Offset errors are introduced by the voltage
divider (R5 and R6) and how closely the ratio of R4/R3 matches R2/R1. The latter value impacts the CMRR of the
difference amplifier, which ultimately translates to an offset error. Because this is a low-side measurement, the
value of VSHUNT is the ground potential for the system load. Therefore, it is important to place a maximum value
on VSHUNT. In this design, the maximum value for VSHUNT is set to 100 mV. Equation 2 calculates the maximum
value of the shunt resistor given a maximum shunt voltage of 100 mV and maximum load current of 1 A.
V
RSHUNT(Max) = SHUNT(Max) = 100 mV = 100 m
ILOAD(Max)
1A
(2)
The tolerance of RSHUNT is directly proportional to cost. For this design, a shunt resistor with a tolerance of 0.5%
was selected. If greater accuracy is required, select a 0.1% resistor or better.
The load current is bidirectional; therefore, the shunt voltage range is –100 mV to 100 mV. This voltage is
12
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divided down by R1 and R2 before reaching the operational amplifier, U1A. Take care to ensure that the voltage
present at the noninverting node of U1A is within the common-mode range of the device. Therefore, it is
important to use an operational amplifier, such as the RS8557, RS8558, RS8559, that has a common-mode
range that extends below the negative supply voltage. Finally, to minimize offset error, note that the RS8557,
RS8558, RS8559 has a typical offset voltage of ±3µV (±20µV maximum). Given a symmetric load current of –
1 A to 1 A, the voltage divider resistors (R5 and R6) must be equal. To be consistent with the shunt resistor, a
tolerance of 0.5% was selected. To minimize power consumption, 10kΩ resistors were used. To set the gain
of the difference amplifier, the common-mode range and output swing of the RS8557, RS8558, RS8559 must
be considered. Equation 3 and Equation 4 depict the typical common-mode range and maximum output swing,
respectively, of the RS8557, RS8558, RS8559 given a 3.3V supply.
-100mV
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