AD5398 Analog Devices, AD5398 Datasheet - Page 12

• Manufacturer Part Number: AD5398
• Description: 120 mA, Current Sinking, 10-Bit, I2C D/A Converter
• Manufacturer: Analog Devices

Specifications of AD5398

• Resolution (bits): 10bit
• Dac Update Rate: 31kSPS
• Dac Settling Time: 250µs
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: I2C/Ser 2-wire,Ser

AD5398
Table 7. Data Format
Serial Data-Words
Serial Data Bits
Input Register
Function
1
POWER SUPPLY BYPASSING AND GROUNDING
When accuracy is important in an application, it is beneficial to
consider power supply and ground return layout on the PCB.
The PCB for the AD5398 should have separate analog and
digital power supply sections. Where shared AGND and DGND
is necessary, the connection of grounds should be made at only
one point, as close as possible to the AD5398.
Special attention should be paid to the layout of the AGND
return path and track between the voice coil motor and I
minimize any series resistance. Figure 21 shows the output
current sink of the AD5398 and illustrates the importance of
reducing the effective series impedance of AGND, and the track
resistance between the motor and I
modelled as inductor L
the voice coil is effectively a dc current that results in a voltage
drop, V
series inductance is minimal. The maximum voltage drop
allowed across R
source voltage of Q1 is 200 mV. This means that the AD5398
output has a compliance voltage of 600 mV. If V
600 mV, the output transistor, Q1, can no longer operate
properly and I
SDA
SDA
SCL
SCL
PD = soft power-down; X = unused/don’t care; D9 to D0 = DAC data.
START BY
START BY
MASTER
MASTER
C
, when the AD5398 is sinking current; the effect of any
1
1
0
0
SINK
0
0
SENSE
might not be maintained as a constant.
ADDRESS BYTE
ADDRESS BYTE
0
0
SERIAL BUS
SERIAL BUS
is 400 mV, and the minimum drain to
FRAME 1
FRAME 1
1
C
High Byte
SD7
R15
PD
and resistor R
1
1
1
1
SD6
R14
X
X
X
SINK
SD5
R13
D9
X
X
. The voice coil is
C
. The current through
R/W
R/W
ACK BY
ACK BY
AD5398
AD5398
SD4
R12
D8
9
9
DROP
PD
PD
1
1
falls below
SD3
R11
D7
X
X
SINK
Figure 19. Write Operation
Figure 20. Read Operation
D9
D9
MOST SIGNIFICANT
MOST SIGNIFICANT
SD2
R10
D6
Rev. B | Page 12 of 16
to
DATA BYTE
DATA BYTE
D8
D8
FRAME 2
FRAME 2
SD1
R9
D5
D7
D7
D6
D6
SD0
R8
D4
D5
D5
D4
D4
Low Byte
SD7
R7
D3
Figure 21. Effect of PCB Trace Resistance and Inductance
ACK BY
ACK BY
AD5398
AD5398
INDUCTANCE
RESISTANCE
1
1
GROUND
GROUND
SD6
R6
D2
D3
D3
R
AGND
SENSE
D2
D2
3.3Ω
R
L
SD5
R5
D1
G
ACTUATOR
G
D1
D1
7
LEAST SIGNIFICANT
LEAST SIGNIFICANT
Q1
VOICE
V
COIL
G
D0
D0
DATA BYTE
DATA BYTE
SD4
R4
D0
FRAME 3
FRAME 3
8
I
R
SINK
X
X
R
L
V
C
T
C
BAT
SD3
R3
X
X
X
V
V
T
DROP
V
C
X
X
TRACE
RESISTANCE
SD2
R2
X
X
X
ACK BY
ACK BY
AD5398
AD5398
9
9
SD1
R1
X
STOP BY
STOP BY
MASTER
MASTER
SD0
R0
X