EVAL-AD5821AEBZ Analog Devices Inc, EVAL-AD5821AEBZ Datasheet - Page 14

• Manufacturer Part Number: EVAL-AD5821AEBZ
• Description: Evaluation Board I.c.
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD5821AEBZ

• Number Of Dac's: 1
• Number Of Bits: 10
• Outputs And Type: 1, Single Ended
• Sampling Rate (per Second): 400k
• Data Interface: I²C
• Settling Time: 250µs
• Dac Type: Current
• Voltage Supply Source: Single
• Operating Temperature: -30°C ~ 80°C
• Utilized Ic / Part: AD5821A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5821A
APPLICATIONS INFORMATION
The AD5821A is designed to drive both spring-preloaded and
nonspring linear motors used in applications such as lens auto-
focus, image stabilization, or optical zoom. The operation principle
of the spring-preloaded motor is that the lens position is controlled
by the balancing of a voice coil and spring. Figure 25 shows the
transfer curve of a typical spring-preloaded linear motor for
autofocus. The key points of this transfer function are displace-
ment or stroke, which is the actual distance the lens moves in
millimeters (mm) and the current through the motor, measured
in milliamps (mA).
A start current is associated with spring-preloaded linear
motors, which is a threshold current that must be exceeded for
any displacement in the lens to occur. The start current is usually
20 mA or greater; the rated stroke or displacement is usually
0.25 mm to 0.4 mm; and the slope of the transfer curve is
approximately 10 μm/mA or less.
The AD5821A is designed to sink up to 120 mA, which is more
than adequate for available commercial linear motors or voice
coils. Another factor that makes the AD5821A the ideal solu-
tion for these applications is the monotonicity of the device,
ensuring that lens positioning is repeatable for the application
of a given digital word.
V
DD
R
P
R
P
SDA
SCL
I
2
C MASTER
DEVICE
XSHUTDOWN
I
2
DEVICE
C SLAVE
Figure 26. Typical Application Circuit
1
3
4
Rev. 0 | Page 14 of 16
INTERFACE
I
2
C SERIAL
5
REFERENCE
AD5821A
Figure 26 shows a typical application circuit for the AD5821A.
OUTPUT DAC
CURRENT
10-BIT
0.1µF
Figure 25. Spring-Preloaded Voice Coil Stroke vs. Sink Current
0.5
0.2
0.1
0.4
0.3
POWER-ON
CURRENT
10
RESET
START
V
R
DD
10µF
6
20
V
+
DD
30
R
2
40
SENSE
0.1µF
V
SINK CURRENT (mA)
CC
50
D1
7
60
10µF
70
8
+
V
80
CC
I
SINK
VOICE
COIL
90 100
110 120