AD8554ARUZ Analog Devices Inc, AD8554ARUZ Datasheet - Page 21

• Manufacturer Part Number: AD8554ARUZ
• Description: IC OPAMP CHOPPER R-R 14TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD8554ARUZ

• Slew Rate: 0.4 V/µs
• Amplifier Type: Chopper (Zero-Drift)
• Number Of Circuits: 4
• Output Type: Rail-to-Rail
• Gain Bandwidth Product: 1.5MHz
• Current - Input Bias: 10pA
• Voltage - Input Offset: 1000µV
• Current - Supply: 850µA
• Current - Output / Channel: 30mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 14-TSSOP
• Op Amp Type: Zero Drift
• No. Of Amplifiers: 4
• Bandwidth: 1.5MHz
• Supply Voltage Range: 2.7V To 5.5V
• Amplifier Case Style: TSSOP
• No. Of Pins: 14
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

A HIGH ACCURACY THERMOCOUPLE AMPLIFIER
Figure 68 shows a K-type thermocouple amplifier configuration
with cold junction compensation. Even from a 5 V supply, the
AD8551 can provide enough accuracy to achieve a resolution of
better than 0.02°C from 0°C to 500°C. D1 is used as a tempera-
ture measuring device to correct the cold junction error from
the thermocouple and should be placed as close as possible to
the two terminating junctions. With the thermocouple measuring
tip immersed in a 0°C ice bath, R
output is at 0 V.
Using the values shown in Figure 68, the output voltage tracks
temperature at 10 mV/°C. For a wider range of temperature
measurement, R
5 mV/°C change at the output, allowing measurements of up
to 1000°C.
THERMOCOUPLE
PRECISION CURRENT METER
Because of its low input bias current and superb offset voltage at
single supply voltages, the AD855x is an excellent amplifier for
precision current monitoring. Its rail-to-rail input allows the
amplifier to be used as either a high-side or low-side current
monitor. Using both amplifiers in the AD8552 provides a simple
method to monitor both current supply and return paths for
load or fault detection.
Figure 69 shows a high-side current monitor configuration. In
this configuration, the input common-mode voltage of the
amplifier is at or near the positive supply voltage. The rail-to-
rail input of the amplifier provides a precise measurement even
with the input common-mode voltage at the supply voltage. The
CMOS input structure does not draw any input bias current,
ensuring a minimum of measurement error.
The 0.1 Ω resistor creates a voltage drop to the noninverting
input of the AD855x. The output of the amplifier is corrected
until this voltage appears at the inverting input. This creates a
current through R
monitor output is given by
40.7µV/°C
K-TYPE
12V
0.1µF
Figure 68. A Precision K-Type Thermocouple Amplifier with
2
9
REF02EZ
can be decreased to 62 kΩ. This creates a
1
, which in turn flows through R
1N4148
4
5.62kΩ
Cold Junction Compensation
D1
R
4
6
R
10.7kΩ
R
2.74kΩ
R
53.6Ω
5.000V
1
2
3
200Ω
R
6
6
should be adjusted until the
R
40.2kΩ
453Ω
5
R
7
124kΩ
2
3
R
–
AD8551
+
8
5V
8
4
0.1µF
10µF
+
2
0V TO 5.00V
(0°C TO 500°C)
. The
1
Rev. D | Page 21 of 24
Using the components shown in Figure 69, the monitor output
transfer function is 2.5 V/A.
Figure 70 shows the low-side monitor equivalent. In this circuit,
the input common-mode voltage to the AD8552 is at or near
ground. Again, a 0.1 Ω resistor provides a voltage drop propor-
tional to the return current. The output voltage is given as
For the component values shown in Figure 70, the output
transfer function decreases from V+ at −2.5 V/A.
PRECISION VOLTAGE COMPARATOR
The AD855x can be operated open-loop and used as a precision
comparator. The AD855x has less than 50 μV of offset voltage
when run in this configuration. The slight increase of offset
voltage stems from the fact that the autocorrection architecture
operates with lowest offset in a closed-loop configuration, that
is, one with negative feedback. With 50 mV of overdrive, the
device has a propagation delay of 15 μs on the rising edge and
8 μs on the falling edge. Ensure the maximum differential
voltage of the device is not exceeded. For more information,
refer to the Input Overvoltage Protection section.
V
Monitor
OUT
MONITOR
=
OUTPUT
V
OUT
( )
V
Figure 69. A High-Side Load Current Monitor
Figure 70. A Low-Side Load Current Monitor
Output
+
3V
−
Si9433
Q1
⎛
⎜
⎜
⎝
100Ω
V+
M1
R
R
R
R
2.49kΩ
R
100Ω
R
=
2
1
SENSE
0.1Ω
2
1
1
S
×
R
AD8551/AD8552/AD8554
D
2
R
R
2.49kΩ
R
2
×
SENSE
SENSE
0.1Ω
⎛
⎜
⎜
⎝
G
R
SENSE
×
R
V+
1
I
2
L
3
1/2 AD8552
⎞
⎟
⎟
⎠
AD8552
⎞
× ⎟ ⎟
⎠
1/2
3V
I
L
RETURN TO
GROUND
I
8
4
L
0.1µF
1
V+
(23)
(24)