AD8624ARUZ-RL Analog Devices Inc, AD8624ARUZ-RL Datasheet - Page 16

• Manufacturer Part Number: AD8624ARUZ-RL
• Description: Quad Precision 36V,Low Power RRO
• Manufacturer: Analog Devices Inc

Specifications of AD8624ARUZ-RL

• Amplifier Type: Voltage Feedback
• Number Of Circuits: 4
• Output Type: Rail-to-Rail
• Slew Rate: 0.48 V/µs
• Gain Bandwidth Product: 560kHz
• Current - Input Bias: 45pA
• Voltage - Input Offset: 10µV
• Current - Supply: 215µA
• Current - Output / Channel: 40mA
• Voltage - Supply, Single/dual (±): ±2.5 V ~ 15 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 14-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD8622/AD8624
HALL SENSOR SIGNAL CONDITIONING
The AD8622/AD8624 is also highly suitable for high accuracy,
low power signal conditioning circuits. One such use is in Hall
sensor signal conditioning (see Figure 57). The magnetic
sensitivity of a Hall element is proportional to the bias voltage
applied across it. With 1 V bias voltage, the Hall element
consumes about 2.5 mA of supply current and has a sensitivity
of 5.5 mV/mT typical. To reduce power consumption, bias
voltage must be reduced, but at the risk of lower sensitivity. The
only way to achieve higher sensitivity is by introducing a gain
using a precision micropower amplifier. The AD8622/AD8624,
with all its features, is well suited to amplify the sensitivity of the
Hall element.
The
A precision voltage reference is required to hold a constant current
so that the Hall voltage only depends on the intensity of the mag-
ADR121 – 2.5V
NOTES
1. USE MATCHED RESISTORS FOR IN-AMP.
2. FOR INFORMATION ON C1, C2, AND C3, REFER TO ADR121 DATA SHEET.
ADR121
V
SY
0.1µF
C2
is a precision micropower 2.5 V voltage reference.
C1
1µF TO 10µF
TO 10µF
0.1µF
C3
+
4.12kΩ
98.8kΩ
R8
R9
AD862x
+
–
V
SY
Figure 57. Hall Sensor Signal Conditioning
ELEMENT
HALL
400Ω
×4
Rev. B | Page 16 of 20
R7
200Ω
+
AD862x
–
–
AD862x
+
V
V
SY
SY
9.9kΩ
9.9kΩ
netic field. Using the 4.12k:98.8k resistive divider, the bias
voltage of the Hall element is reduced to 100 mV, leading to only
250 μA of power consumption. The 3-op-amp in-amp
configuration of the AD8622/AD8624 then increases the
sensitivity to 55 mV/mT. The key to high CMRR for this in-amp
configuration are resistors that are well matched (where R1/R2
= R3/R4) from both the resistive ratio and relative drift. The
resistors are important in determining the performance over
manufacturing tolerances, time and temperature. At least 1% or
better resistors are recommended. Using the AD8622/AD8624 to
amplify the sensor signal can reduce power while also achieving
higher sensitivity. The total current consumed is just 1.2 mA,
resulting in 21× improvement in sensitivity/power.
R5
R6
9.9kΩ
9.9kΩ
R1
R3
R4
9.9kΩ
AD862x
–
+
9.9kΩ
V
R2
SY
V
OUT
= 2.5V +
55mV
mT
× MAGNETIC FIELD (mT)