AD5300BRMZ Analog Devices Inc, AD5300BRMZ Datasheet - Page 11

• Manufacturer Part Number: AD5300BRMZ
• Description: IC DAC 8BIT R-R 2.7-5.5V 8-MSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5300BRMZ

• Data Interface: Serial
• Settling Time: 4µs
• Number Of Bits: 8
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 1.4mW
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Resolution (bits): 8bit
• Sampling Rate: 250kSPS
• Input Channel Type: Serial
• Supply Voltage Range - Analog: 2.7V To 5.5V
• Supply Current: 140µA
• Digital Ic Case Style: SOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Two 8-Bit AD5300s Together Make One 15-Bit DAC
By using the configuration in Figure 31, it can be seen that one
15-bit DAC can be made with two 8-bit AD5300s. Because of
the low supply current the AD5300 requires, the output of one
DAC may be directed into the supply pin of the second DAC.
The first DAC has no problem sourcing the required 140 µA
of current for the second DAC.
Since the AD5300 works on any supply voltage between 2.5 V
and 5.5 V, the output of the first DAC can be anywhere above
2.5 V. For a V
its output range (2.5 V to 5 V), which gives 7-bit resolution on
the output voltage. This output then becomes the supply and
reference for the second DAC. The second DAC has 8-bit reso-
lution on the output range, which gives an overall resolution for
the system of 15 bits.
A level-shifter is required to ensure that the logic input voltages
do not exceed the supply voltage of the part. The microcontroller
outputs 5 V signals, which need to be level shifted down to 2.5 V
in the case of the second DAC having a supply of only 2.5 V.
Using AD5300 with an Opto-Isolated Interface
In process-control applications in industrial environments, it is
often necessary to use an opto-isolated interface to protect and
isolate the controlling circuitry from any hazardous common-
mode voltages that may occur in the area where the DAC is
functioning. Opto-isolators provide isolation in excess of 3 kV.
Because the AD5300 uses a 3-wire serial logic interface, it
requires only three opto-isolators to provide the required isola-
tion (see Figure 32). The power supply to the part also needs to
be isolated. This 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 AD5300.
REV.
CONTROLLER
+5V
D
MICRO-
Figure 30. Bipolar Operation with the AD5300
Figure 31. 15-Bit DAC Using Two AD5300s
10 F
DD
of 5 V, this allows the first DAC to use half of
SYNC
DIN
SCLK
0.1 F
SHIFTER
LEVEL
5V
V
AD5300
DD
INTERFACE
R1 = 10k
V
AD5300
DD
3-WIRE
SERIAL
SYNC
SCLK
DIN
V
OUT
V
AD5300
OUT
V
DD
= 2.5V TO 5V
AD820/
OP295
R2 = 10k
+5V
–5V
V
15-BIT
RESOLUTION
OUT
= 0V TO 5V
5V
–11–
Power Supply Bypassing and Grounding
When accuracy is important in a circuit, it is helpful to carefully
consider the power supply and ground return layout on the
board. The printed circuit board containing the AD5300 should
have separate analog and digital sections, each having its own
area of the board. If the AD5300 is in a system where other
devices require an AGND to DGND connection, the connec-
tion should be made at one point only. This ground point should
be as close as possible to the AD5300.
The power supply to the AD5300 should be bypassed with
10 µF and 0.1 µF capacitors. The capacitors should be physi-
cally as close as possible to the device with the 0.1 µF capacitor
ideally right up against the device. The 10 µF capacitors are the
tantalum bead type. It is important that the 0.1 µF capacitor
has low effective series resistance (ESR) and effective series
inductance (ESI), e.g., common ceramic types of capacitors. This
0.1 µF capacitor provides a low impedance path to ground for
high frequencies caused by transient currents due to internal
logic switching.
The power supply line itself should have as large a trace as pos-
sible to provide a low impedance path and reduce glitch effects
on the supply line. Clocks and other fast switching digital signals
should be shielded from other parts of the board by digital
ground. Avoid crossover of digital and analog signals if possible.
When traces cross on opposite sides of the board, ensure that
they run at right angles to each other to reduce feedthrough
effects through the board. The best board layout technique is
the microstrip technique where the component side of the board
is dedicated to the ground plane only and the signal traces are
placed on the solder side. However, this is not always possible
with a 2-layer board.
POWER
Figure 32. AD5300 with an Opto-Isolated Interface
SYNC
DATA
SCLK
V
V
V
DD
DD
DD
10k
10k
10k
REGULATOR
5V
SCLK
SYNC
DIN
AD5300
GND
V
DD
10 F
V
OUT
AD5300
0.1 F