
REV. A
AD22151
–3–
PIN CONFIGURATION
TOP VIEW
(Not to Scale)
8
7
6
5
1
2
3
4
AREA OF SENSITIVITY*
TC1
TC2
TC3
GND
VCC
REF
GAIN
OUTPUT
AD22151
(Not to Scale)
8
7
6
5
1
2
3
4
*SHADED AREA REPRESENTS
MAGNETIC FIELD AREA OF
SENSITIVITY (20MILS
20MILS)
POSITIVE B FIELD INTO TOP OF
PACKAGE RESULTS IN A POSITIVE
VOLTAGE RESPONSE
CIRCUIT OPERATION
The AD22151 consists of epi Hall plate structures located at the
center of the die. The Hall plates are orthogonally sampled by
commutation switches via a differential amplifier. The two
amplified Hall signals are synchronously demodulated to provide a
resultant offset cancellation (see Figure 3). The demodulated
signal passes through a noninverting amplifier to provide final
gain and drive capability. The frequency at which the output
signal is refreshed is 50 kHz.
TEMPERATURE – C
140
–40
120
100
80
60
40
20
0
–20
–0.004
OFFSET
–
V
–0.003
–0.002
–0.001
0
0.001
0.002
0.003
0.004
0.005
Figure 3. Relative Quiescent Offset vs. Temperature
TEMPERATURE DEPENDENCIES
The uncompensated gain temperature coefficient (GTCU) of the
AD22151 is the result of fundamental physical properties asso-
ciated with silicon bulk Hall plate structures. Low doped Hall
plates operated in current bias mode exhibit a temperature
relationship determined by the action of scattering mechanisms
and doping concentration.
The relative value of sensitivity to magnetic field can be altered
by the application of mechanical force upon silicon. The mecha-
nism is principally the redistribution of electrons throughout the
PIN FUNCTION DESCRIPTIONS
Pin No.
Description
Connection
1Temperature Compensation 1
Output
2Temperature Compensation 2
Output
3Temperature Compensation 3
Input/Output
4Ground
5Output
Output
6
Gain
Input
7Reference
Output
8
Positive Power Supply
“valleys” of the silicon crystal. Mechanical force on the sensor is
attributable to package-induced stress. The package material
acts to distort the encapsulated silicon, altering the Hall cell
gain by
±2% and GTCU by ±200 ppm.
Figure 4 shows the typical GTCU characteristic of the AD22151.
This is the observable alteration of gain with respect to tempera-
ture with Pin 3 (TC3) held at a constant 2.5 V (uncompensated).
If a permanent magnet source used in conjunction with the
sensor also displays an intrinsic TC (BTC), it will require factoring
into the total temperature compensation of the sensor assembly.
Figures 5 and 6 represent typical overall temperature/gain per-
formance for a sensor and field combination (BTC = –200 ppm).
Figure 5 is the total drift in volts over a –40
∞C to +150∞C tem-
perature range with respect to applied field. Figure 6 represents
typical percentage gain variation from 25
∞C. Figures 7 and 8
show similar data for a BTC = –2000 ppm.
TEMPERATURE – C
14
–4
–40
%
GAIN
10
60
110
160
12
4
2
0
–2
10
6
8
–6
Figure 4. Uncompensated Gain Variation (from
25
∞C) vs. Temperature