AD5415YRU-REEL AD [Analog Devices], AD5415YRU-REEL Datasheet - Page 15

• Manufacturer Part Number: AD5415YRU-REEL
• Description: Dual 12-Bit, High Bandwidth, Multiplying DAC with 4-Quadrant Resistors and Serial Interface
• Manufacturer: AD [Analog Devices]

GENERAL DESCRIPTION
DAC SECTION
The AD5415 is a 12-bit, dual-channel, current output DAC
consisting of standard inverting R to 2R ladder configuration. A
simplified diagram of one DAC channel for the AD5415 is
shown in Figure 32. The feedback resistor R
The value of R is typically 10 kΩ (minimum 8 kΩ and
maximum 12 kΩ). If I
potential, a constant current flows in each ladder leg, regardless
of the digital input code. Therefore, the input resistance
presented at V
Access is provided to the V
the DAC, making the device extremely versatile and allowing it
to be configured in several different operating modes, for
example, to provide a unipolar output, bipolar output, or in
single-supply modes of operation in unipolar mode or
4-quadrant multiplication in bipolar mode.
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 33. When an output amplifier
is connected in unipolar mode, the output voltage is given by
V
REF
A
2R
REF
S1
R
DAC DATA LATCHES
is always constant.
AND DRIVERS
2R
Figure 32. Simplified Ladder
S2
OUT
R
1 and I
2R
REF
S3
, R
AGND
OUT
FB
R
, I
R2_3A
2 are kept at the same
OUT
R2A
R3A
2R
S12
1, and I
V
FB
DD
2R
V
NOTES:
1
2
DAC B OMITTED FOR CLARITY.
C1 PHASE COMPENSATION (1pF TO 2pF) MAY BE REQUIRED,
IF A1 IS A HIGH SPEED AMPLIFIER.
REF
has a value of 2R.
R3
2R
OUT
R2
2R
2R
A
R1A
2 terminals of
R
I
I
OUT
OUT
SYNC
FB
R1
2R
uCONTROLLER
A
12-BIT DAC A
Figure 33. Unipolar Operation
1A
2A
AD5415
SCLK
Rev. 0 | Page 15 of 28
R
R
2R
FB
SDIN
AGND
GND
I
I
OUT
OUT
where:
D is the fractional representation of the digital word loaded to
the DAC, in the range of 0 to 4095.
n is the number of bits.
Note that the output voltage polarity is opposite the V
polarity for dc reference voltages.
These DACs are designed to operate with either negative or
positive reference voltages. The V
the internal digital logic to drive the DAC switches’ on and off
states.
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 32 gives a
unipolar 0 V to −10 V output voltage swing. When V
signal, the circuit performs 2-quadrant multiplication.
Table 5 shows the relationship between digital code and
expected output voltage for unipolar operation.
Table 5. Unipolar Code Table
Digital Input
1111 1111
1000 0000
0000 0001
0000 0000
R
FB
1A
2A
A
V
AGND
OUT
C1
= −V
A1
REF
V
× D/2
OUT
= 0V TO –V
n
IN
DD
Analog Output (V)
−V
−V
−V
−V
power pin is used only by
REF
REF
REF
REF
(4095/4096)
(2048/4096) = −V
(1/4096)
(0/4096) = 0
IN
AD5415
REF
is an ac
REF
/2