AD5643R Analog Devices, AD5643R Datasheet - Page 26

• Manufacturer Part Number: AD5643R
• Manufacturer: Analog Devices

Specifications of AD5643R

• Resolution (bits): 14bit
• Dac Update Rate: 250kSPS
• Dac Settling Time: 3.5µs
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Voltage Out
• Dac Input Format: Ser,SPI

AD5623R/AD5643R/AD5663R
APPLICATIONS INFORMATION
USING A REFERENCE AS A POWER SUPPLY
Because the supply current required by the AD5623R/AD5643R/
AD5663R is extremely low, an alternative option is to use a
voltage reference to supply the required voltage to the parts (see
Figure 60). This is especially useful if the power supply is quite
noisy or if the system supply voltages are at some value other
than 5 V or 3 V, for example, 15 V. The voltage reference outputs
a steady supply voltage for the AD5623R/AD5643R/ AD5663R.
If the low dropout
current to the AD5623R/AD5643R/AD5663R, with no load on
the output of the DAC. When the DAC output is loaded, the
REF195 also needs to supply the current to the load. The total
current required (with a 5 kΩ load on the DAC output) is
The load regulation of the REF195 is typically 2 ppm/mA,
which results in a 3 ppm (15 μV) error for the 1.5 mA current
drawn from it. This corresponds to a 0.196 LSB error.
BIPOLAR OPERATION USING THE AD5663R
The AD5663R has been designed for single-supply operation,
but a bipolar output range is also possible using the circuit in
Figure 61. The circuit gives an output voltage range of ±5 V.
Rail-to-rail operation at the amplifier output is achievable using
an
The output voltage for any input code can be calculated as
follows:
where D represents the input code in decimal (0 to 65,535).
With V
Figure 60. REF195 as Power Supply to the AD5623R/AD5643R/AD5663R
AD820
THREE-WIRE
500 μA + (5 V/5 kΩ) = 1.25 mA
INTERFACE
V
DD
SERIAL
O
= 5 V, R1 = R2 = 10 kΩ,
=
or an
⎡
⎢
⎣
V
DD
OP295
SYNC
SCLK
×
REF195
DIN
⎛
⎜
⎝
15V
65
V
REF195
O
D
,
536
as the output amplifier.
=
is used, it must supply 500 μA of
⎛
⎜
⎝
⎞
⎟
⎠
10
65
×
,
×
⎛
⎜
⎝
536
5V
AD5623R/
AD5643R/
R1
AD5663R
D
R1
⎞
⎟
⎠
+
V
DD
−
R2
5
⎞
⎟
⎠
V
−
V
V
DD
OUT
×
= 0V TO 5V
⎛
⎜
⎝
R2
R1
⎞
⎟
⎠
⎤
⎥
⎦
Rev. D | Page 26 of 32
This is an output voltage range of ±5 V, with 0x0000 corre-
sponding to a −5 V output, and 0xFFFF corresponding to a
+5 V output.
USING THE AD5663R WITH A
GALVANICALLY ISOLATED INTERFACE
In process control applications in industrial environments,
it is often necessary to use a galvanically isolated interface to
protect and isolate the controlling circuitry from any hazardous
common-mode voltages that can occur in the area where
the DAC is functioning. iCoupler® provides isolation in excess
of 2.5 kV. The AD5663R uses a 3-wire serial logic interface, so
the ADuM1300 3-channel digital isolator provides the required
isolation (see Figure 62). The power supply to the part also
needs to be isolated, which is done by using a transformer. On
the DAC side of the transformer, a 5 V regulator provides the
5 V supply required for the AD5663R.
+5V
DATA
SCLK
SDI
POWER
Figure 62. AD5663R with a Galvanically Isolated Interface
10µF
Figure 61. Bipolar Operation with the AD5663R
V
V
V
IA
IB
IC
ADuM1300
0.1µF
V
V
V
OA
OB
OC
V
THREE-WIRE
DD
AD5663R
INTERFACE
R1 = 10kΩ
SERIAL
REGULATOR
V
5V
SCLK
SYNC
DIN
OUT
AD5663R
GND
V
DD
AD820/
OP295
R2 = 10kΩ
+5V
–5V
V
10µF
OUT
0.1µF
±5V