AD5305_06 Datasheet, PDF (20/24 Pages) Analog Devices – 2.5 V to 5.5 V, 500 μA, 2-Wire Interface Interface

AD5305/AD5315/AD5325
APPLICATIONS
TYPICAL APPLICATION CIRCUIT
The AD5305/AD5315/AD5325 can be used with a wide range
of reference voltages where the devices offer full, one-quadrant
multiplying capability over a reference range of 0 V to VDD.
More typically, these devices are used with a fixed, precision
reference voltage. Suitable references for 5 V operation are the
AD780 and REF192 (2.5 V references). For 2.5 V operation, a
suitable external reference is the AD589, a 1.23 V band gap
reference. Figure 36 shows a typical setup for the AD5305/
AD5315/AD5325 when using an external reference. Note that
A0 can be high or low.
V_DD = 2.5V TO 5.5V
0.1µF
10µF
V_IN
V_OUT
EXT
1µF
REF
AD780/REF192
WITH V_DD = 5V
OR AD589 WITH
V_DD = 2.5V
REFIN
AD5305/
AD5315/
AD5325
V_OUTA
V_OUTB
SCL
SDA
A0
GND
V_OUTC
V_OUTD
SERIAL
INTERFACE
Figure 36. AD5305/AD5315/AD5325 Using External Reference
If an output range of 0 V to VDD is required, the simplest
solution is to connect the reference input to VDD. As this
supply may not be very accurate and may be noisy, the
AD5305/AD5315/AD5325 can be powered from the reference
voltage; for example, using a 5 V reference such as the REF195.
The REF195 outputs a steady supply voltage for the AD5305/
AD5315/AD5325. The typical current required from the
REF195 is 600 μA supply current and approximately 112 μA
into the reference input. This is with no load on the DAC
outputs. When the DAC outputs are loaded, the REF195 also
needs to supply the current to the loads. The total current
required (with a 10 kΩ load on each output) is
712 μA + 4(5 V/10 kΩ) = 2.70 mA
The load regulation of the REF195 is typically 2 ppm/mA,
which results in an error of 5.4 ppm (27 μV) for the 2.7 mA
current drawn from it. This corresponds to a 0.0014 LSB error
at eight bits and 0.022 LSB error at 12 bits.
BIPOLAR OPERATION
The AD5305/AD5315/AD5325 have been designed for single
supply operation, but a bipolar output range is also possible using
the circuit in Figure 37. This circuit gives an output voltage
range of 5 V. Rail-to-rail operation at the amplifier output is
achievable using an AD820 or an OP295 as the output amplifier.
6V TO 12V
10µF
0.1µF
+5V
AD1585
V_IN
V_OUT
GND
1µF
R1 = 10kΩ
V_DD
V_OUTA
AD5305
REFIN ^VOUTB
V_OUTC
V_OUTD
A0
GND SCL SDA
R2 = 10kΩ
+5V
AD820/
OP295
±5V
–5V
2-WIRE
SERIAL
INTERFACE
Figure 37. Bipolar Operation with the AD5305
The output voltage for any input code can be calculated as
follows:
( ( )) ⎡ REFIN × D /2^N
V_OUT
=⎢
⎢⎣
R1
× (R1 + R2) _{− REFIN × (R2 / R1)⎥⎤}
⎥⎦
where:
D is the decimal equivalent of the code loaded to the DAC.
N is the DAC resolution.
REFIN is the reference voltage input.
with
REFIN = 5 V, R1 = R2 = 10 kΩ, VOUT (10 × D/2^N) − 5 V
MULTIPLE DEVICES ON ONE BUS
Figure 38 shows two AD5305 devices on the same serial bus.
Each has a different slave address because the state of the A0 pin
is different. This allows each of eight DACs to be written to or
read from independently.
V_DD
PULL-UP
RESISTORS
A0
AD5305
SDA SCL
MICRO-
CONTROLLER
Rev. G | Page 20 of 24
SDA
SCL
A0 _AD5305
Figure 38. Multiple AD5305 Devices on One Bus