AD5452 Analog Devices, AD5452 Datasheet - Page 16

• Manufacturer Part Number: AD5452
• Description: 12-Bit High Bandwidth Multiplying DACs with Serial Interface
• Manufacturer: Analog Devices

Specifications of AD5452

• Resolution (bits): 12bit
• Dac Update Rate: 2.7MSPS
• Dac Settling Time: 160ns
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Ser,SPI

AD5450/AD5451/AD5452/AD5453
GENERAL DESCRIPTION
DAC SECTION
The AD5450/AD5451/AD5452/AD5453 are 8-/10-/12-/14-bit
current output DACs, respectively, consisting of a segmented
(4-bit) inverting R-2R ladder configuration. A simplified
diagram for the 12-bit AD5452 is shown in Figure 43.
The feedback resistor, R
typically 9 kΩ (with a minimum value of 7 kΩ and a maximum
value of 11 kΩ). If I
constant current flows in each ladder leg, regardless of digital
input code. Therefore, the input resistance presented at V
always constant and nominally of value R. The DAC output
(I
capacitances. When choosing the 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
DAC, making the device extremely versatile and allowing it to be
configured in several operating modes; for example, it can provide
a unipolar output or can provide 4-quadrant multiplication in
bipolar mode. Note that a matching switch is used in series with
the internal R
R
CIRCUIT OPERATION
Unipolar Mode
Using a single op amp, these devices can easily be configured to
provide a 2-quadrant multiplying operation or a unipolar output
voltage swing, as shown in Figure 44. 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.
D
n is the number of bits.
FB
OUT
, power must be applied to V
1) is code-dependent, producing various resistances and
= 0 to 255 (8-bit AD5450).
= 0 to 1023 (10-bit AD5451).
= 0 to 4095 (12-bit AD5452).
= 0 to 16,383 (14-bit AD5453).
V
V
REF
OUT
=
−
FB
2R
S1
2
D
feedback resistor. If users attempt to measure
R
n
Figure 43. AD5452 Simplified Ladder
DAC DATA LATCHES
×
OUT
V
AND DRIVERS
2R
S2
REF
1 is kept at the same potential as GND, a
R
FB
, has a value of R. The value of R is
REF
2R
S3
, R
DD
FB
to achieve continuity.
R
, and I
2R
S12
OUT
1 terminals of the
2R
R
AGND
R
I
OUT
FB
REF
1
is
Rev. E | Page 16 of 32
Note that the output voltage polarity is opposite to the V
polarity for dc reference voltages.
V
NOTES
1. R1 AND R2 USED ONLY IF GAIN ADJUSTMENT IS REQUIRED.
2. C1 PHASE COMPENSATION (1pF TO 2pF) MAY BE REQUIRED
These DACs are designed to operate with either negative or
positive reference voltages. The V
the internal digital logic to drive the on and off states of the
DAC switches.
These DACs are designed to accommodate ac reference input
signals in the range of −10 V to +10 V.
With a fixed 10 V reference, the circuit shown in Figure 44 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 the digital code and
the expected output voltage for a unipolar operation using the
8-bit AD5450.
Table 5. Unipolar Code Table for the AD5450
Digital Input
1111 1111
1000 0000
0000 0001
0000 0000
REF
IF A1 IS A HIGH SPEED AMPLIFIER.
R1
V
SYNC
REF
V
V
µCONTROLLER
DD
DD
Figure 44. Unipolar Mode Operation
AD5450/
AD5451/
AD5452/
AD5453
SCLK SDIN
Analog Output (V)
−V
−V
−V
−V
REF
REF
REF
REF
R
(255/256)
(128/256) = −V
(1/256)
(0/256) = 0
FB
I
OUT
GND
DD
R2
1
power pin is only used by
AGND
REF
C1
/2
A1
V
OUT
= 0 TO –V
IN
REF
is an ac
REF