EVAL-AD5447EBZ Analog Devices Inc, EVAL-AD5447EBZ Datasheet - Page 16

• Manufacturer Part Number: EVAL-AD5447EBZ
• Description: BOARD EVALUATION FOR AD5447
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD5447EBZ

• Number Of Dac's: 2
• Number Of Bits: 12
• Outputs And Type: 2, Single Ended
• Sampling Rate (per Second): 21.3M
• Data Interface: Parallel
• Settling Time: 80ns
• Dac Type: Current
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 125°C
• Utilized Ic / Part: AD5447
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5428/AD5440/AD5447
GENERAL DESCRIPTION
DAC SECTION
The AD5428/AD5440/AD5447 are CMOS 8-, 10-, and 12-bit,
dual-channel, current output DACs consisting of a standard
inverting R-2R ladder configuration. Figure 37 shows a simplified
diagram for a single channel of the 8-bit AD5428. The feedback
resistor R
(with a minimum of 8 kΩ and a maximum of 12 kΩ). If I
and AGND are kept at the same potential, a constant current
flows into each ladder leg, regardless of digital input code.
Therefore, the input resistance presented at V
constant and nominally of value R. The DAC output (I
code-dependent, producing various resistances and
capacitances. When choosing an external amplifier, take into
account the variation in impedance generated by the DAC on
the amplifier’s inverting input node.
Access is provided to the V
and DAC B, making the devices extremely versatile and
allowing them to be configured in several operating modes,
such as unipolar output mode, 4-quadrant multiplication
bipolar mode, or single-supply mode. Note that a matching
switch is used in series with the internal R
If users attempt to measure R
to achieve continuity.
V
REF
FB
A has a value of R. The value of R is typically 10 kΩ
S1
2R
DAC DATA LATCHES
R
AND DRIVERS
Figure 37. Simplified Ladder
S2
2R
R
REF
2R
S3
FB
, R
R
A, power must be applied to V
FB
, and I
S8
2R
2R
OUT
FB
R
A feedback resistor.
terminals of DAC A
REF
R
I
AGND
OUT
A is always
FB
A
A
OUT
OUT
) is
1
Rev. B | Page 16 of 32
DD
CIRCUIT OPERATION
Unipolar Mode
Using a single op amp, these devices can easily be configured to
provide 2-quadrant multiplying operation or a unipolar output
voltage swing, as shown in Figure 38. When an output amplifier
is connected in unipolar mode, the output voltage is given by
where:
D is the fractional representation of the digital word loaded to
the DAC.
n is the resolution of the DAC.
Note that the output voltage polarity is opposite to the V
polarity for dc reference voltages. These DACs are designed to
operate with either negative or positive reference voltages. The
V
the on and off states of the DAC switches.
These DACs are also designed to accommodate ac reference
input signals in the range of –10 V to +10 V.
With a fixed 10 V reference, the circuit in Figure 38 gives a
unipolar 0 V to –10 V output voltage swing. When V
signal, the circuit performs 2-quadrant multiplication.
Table 7 shows the relationship between digital code and the
expected output voltage for unipolar operation using the 8-bit
AD5428.
Table 7. Unipolar Code
Digital Input
1111 1111
1000 0000
0000 0001
0000 0000
DD
D = 0 to 255 (8-bit AD5428)
= 0 to 1023 (10-bit AD5440)
= 0 to 4095 (12-bit AD5447)
power pin is only used by the internal digital logic to drive
V
OUT
=
−
V
REF
×
D
Analog Output (V)
–V
–V
–V
–V
2 /
REF
REF
REF
REF
n
(128/256) = –V
(255/256)
(1/256)
(0/256) = 0
REF
/2
IN
is an ac
REF