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AD5446 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD5446
Beschreibung (AD5424 - AD5547) High Bandwidth Multiplying DACs
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 20 Seiten
AD5446 Datasheet, Funktion
Dual Current Output, Parallel Input, 16-/14-Bit
Multiplying DACs with 4-Quadrant Resistors
AD5547/AD5557
FEATURES
Dual channel
16-bit resolution: AD5547
14-bit resolution: AD5557
2- or 4-quadrant, 4 MHz BW multiplying DAC
±1 LSB DNL
±1 LSB INL for AD5557, ±2 LSB INL for AD5547
Operating supply voltage: 2.7 V to 5.5 V
Low noise: 12 nV/√Hz
Low power: IDD = 10 µA max
0.5 µs settling time
Built-in RFB facilitates current-to-voltage conversion
Built-in 4-quadrant resistors allow 0 V to –10 V, 0 V to +10 V,
or ±10 V outputs
2 mA full-scale current ± 20%, with VREF = 10 V
Extended automotive operating temperature range:
–40°C to +125°C
Selectable zero-scale/midscale power-on presets
Compact TSSOP-38 package
APPLICATIONS
Automatic test equipment
Instrumentation
Digitally controlled calibration
Digital waveform generation
GENERAL DESCRIPTION
The AD5547/AD5557 are dual precision, 16-/14-bit,
multiplying, low power, current-output, parallel input, digital-
to-analog converters. They are designed to operate from single
+5 V supply with ±10 V multiplying references for 4-quadrant
outputs with up to 4 MHz bandwidth.
VREF
U1
–VREF
C1
FUNCTIONAL BLOCK DIAGRAM
R1A
RCOMA VREFA ROFSA
VDD
D0–D15
(AD5547)
D0–D13
(AD5557)
D0..D15
OR
D0..D13
WR
A0, A1
DAC A
DAC B
ADDR
DECODE
INPUT
REGISTER
RS
DAC A
REGISTER
RS
DAC A
INPUT
REGISTER
RS
DAC B
REGISTER
RS
DAC B
POWER
ON
RESET
AD5547/AD5557
RFBA
IOUTA
AGNDA
AGNDB
IOUTB
RFBB
ROFSB
DGND
RS MSB LDAC
Figure 1.
R1B
RCOMB VREFB
The built-in 4-quadrant resistors facilitate resistance matching
and temperature tracking, which minimize the numbers of
components needed for multiquadrant applications. In addition,
the feedback resistor (RFB) simplifies the I-V conversion with an
external buffer.
The AD5547/AD5557 are available in a compact TSSOP-38
package and operate at the extended automotive temperature
range of –40°C to +125°C.
16/14 DATA
R1A RCOMA VREFA
R1 R2
AD5547/AD5557
POWER-ON
RESET
ROFSA RFBA
ROFS
16-/14-BIT
DAC A
RFB
IOUTA
AGNDA
C2
U2
VOUTA
–VREF TO +VREF
WR
LDAC
RS
MSB
A0, A1
WR LDAC RS
MSB A0, A1
2 (ONE CHANNEL SHOWN ONLY)
Figure 2. 16/14-Bit 4-Quadrant Multiplying DAC with Minimum of External Components (Only One Channel Shown)
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.






AD5446 Datasheet, Funktion
AD5547/AD5557
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
D1 1
D0 2
ROFSA 3
RFBA 4
R1A 5
RCOMA 6
VREFA 7
IOUTA 8
AGNDA 9
DGND 10
AGNDA 11
IOUTB 12
VREFB 13
RCOMB 14
R1B 15
RFBB 16
ROFSB 17
WR 18
A0 19
AD5547
TOP VIEW
(Not to Scale)
38 D2
37 D3
36 D4
35 D5
34 D6
33 D7
32 D8
31 D9
30 D10
29 VDD
28 D11
27 D12
26 D13
25 D14
24 D15
23 RS
22 MSB
21 LDAC
20 A1
Figure 4. AD5547 TSSOP-38 Pin Configuration
NC 1
NC 2
ROFSA
RFBA
R1A
RCOMA
VREFA
IOUTA
AGNDA
3
4
5
6
7
8
9
DGND 10
AGNDB 11
IOUTB 12
VREFB 13
RCOMB 14
R1B 15
RFBB 16
ROFSB 17
WR 18
A0 19
AD5557
TOP VIEW
(Not to Scale)
38 D0
37 D1
36 D2
35 D3
34 D4
33 D5
32 D6
31 D7
30 D8
29 VDD
28 D9
27 D10
26 D11
25 D12
24 D13
23 RS
22 MSB
21 LDAC
20 A1
NC = NO CONNECT
Figure 5. AD5557 TSSOP-38 Pin Configuration
Table 3. AD5547 Pin Function Descriptions
Pin No. Mnemonic Function
1, 2, 24– D0–D15
28, 30–38
Digital Input Data Bits D0 to D15. Signal level must be ≤ VDD + 0.3 V.
3
ROFSA
Bipolar Offset Resistor A. Accepts up to ±18 V. In 2-quadrant mode, ROFSA ties to RFBA. In 4-quadrant mode, ROFSA
ties to R1A and the external reference.
4 RFBA Internal Matching Feedback Resistor A. Connects to the external op amp for I-V conversion.
5 R1A 4-Quandrant Resistor. In 2-quadrant mode, R1A shorts to the VREFA pin. In 4-quadrant mode, R1A ties to ROFSA. Do
not connect when operating in unipolar mode.
6
RCOMA
Center Tap Point of the Two 4-Quadrant Resistors, R1A and R2A. In 4-quadrant mode, RCOMA ties to the inverting
node of the reference amplifier. In 2-quadrant mode, RCOMA shorts to the VREF pin. Do not connect if operating in
unipolar mode.
7 VREFA DAC A Reference Input in 2-Quadrant Mode, R2 Terminal in 4-Quadrant Mode. In 2-quadrant mode, VREFA is the
reference input with constant input resistance versus code. In 4-quadrant mode, VREFA is driven by the external
reference amplifier.
8 IOUTA DAC A Current Output. Connects to the inverting terminal of external precision I-V op amp for voltage output.
9
AGNDA
DAC A Analog Ground.
10
DGND
Digital Ground.
11
AGNDB
DAC B Analog Ground.
12 IOUTB DAC B Current Output. Connects to inverting terminal of external precision I-V op amp for voltage output.
13 VREFB DAC B Reference Input Pin. Establishes DAC full-scale voltage. Constant input resistance versus code. If
configured with an external op amp for 4-quadrant multiplying, VREFB becomes –VREF.
14
RCOMB
Center Tap Point of the Two 4-Quadrant Resistors, R1B and R2B. In 4-quadrant mode, RCOMB ties to the inverting
node of the reference amplifier. In 2-quadrant mode, RCOMB shorts to the VREF pin. Do not connect if operating in
unipolar mode.
15 R1B
4-Quandrant Resistor. In 2-quadrant mode, R1B shorts to the VREFB pin. In 4-quadrant mode, R1B ties to ROFSB. Do not
connect if operating in unipolar mode.
16 RFBB Internal Matching Feedback Resistor B. Connects to external op amp for I-V conversion.
17
ROFSB
Bipolar Offset Resistor B. Accepts up to ±18 V. In 2-quadrant mode, ROFSB ties to RFBB. In 4-quadrant mode, ROFSB
ties to R1B and an external reference.
Rev. 0 | Page 6 of 20

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AD5446 pdf, datenblatt
AD5547/AD5557
CIRCUIT OPERATION
D/A CONVERTER SECTION
The AD5547/AD5557 are 16-/14-bit, multiplying, current
output, parallel input DACs. The devices operate from a single
2.7 V to 5.5 V supply, and provide both unipolar (0 V to –VREF
or 0 V to +VREF), and bipolar (±VREF) output ranges from –18 V
to +18 V references. In addition to the precision conversion RFB
commonly found in current output DACs, there are three addi-
tional precision resistors for 4-quadrant bipolar applications.
The AD5547/AD5557 consist of two groups of precision R-2R
ladders, which make up the 12/10 LSBs, respectively. Further-
more, the 4 MSBs are decoded into 15 segments of resistor value
2R. Figure 19 shows the architecture of the 16-bit AD5547. Each
of the 16 segments and the R-2R ladder carries an equally
weighted current of one-sixteenth of full scale. The feedback
resistor RFB and 4-quadrant resistor ROFS have values of 10 kΩ.
Each 4-quadrant resistor, R1 and R2, equals 5 kΩ. In 4-quadrant
operation, R1, R2, and an external op amp work together to
invert the reference voltage and apply it to the VREF input.
With ROFS and RFB connected as shown in Figure 2, the output
can swing from –VREF to +VREF.
The reference voltage inputs exhibit a constant input resistance
of 5 kΩ ± 20%. The impedance of IOUT, the DAC output, is code
dependent. External amplifier choice should take into account
the variation of the AD5547/AD5557 output impedance. The
feedback resistance in parallel with the DAC ladder resistance
dominates output voltage noise. To maintain good analog
performance, it is recommended that the power supply is
bypassed with a 0.01 µF to 0.1 µF ceramic or chip capacitor in
parallel with a 1 µF tantalum capacitor. Also, to minimize gain
error, PCB metal traces between VREF and RFB should match.
Every code change of the DAC corresponds to a step function;
gain peaking at each output step may occur if the op amp has
limited GBP and excessive parasitic capacitance present at the
op amp’s inverting node. A compensation capacitor, therefore,
may be needed between the I-V op amp inverting and output
nodes to smooth the step transition. Such a compensation
capacitor should be found empirically, but a 20 pF capacitor is
generally adequate for the compensation.
The VDD power is used primarily by the internal logic to drive
the DAC switches. Note that the output precision degrades if the
operating voltage falls below the specified voltage. Users should
also avoid using switching regulators because device power
supply rejection degrades at higher frequencies.
VREF
R2
5k
RCOM
R1
5k
R1
2R 2R 2R
80k80k80k
2R
80k
RRRRRRRR
40k40k40k40k40k40k40k40k
2R 2R 2R 2R 2R 2R 2R 2R 2R
80k80k80k80k80k80k80k80k80k
RA R R R R
RB
2R 2R 2R 2R 2R
80k80k80k80k80k
4-BIT R2R
15 8
4
ADDRESS DECODER
4 MSB
15 SEGMENTS
8-BIT R2R
ROFS
RFB
10k10k
IOUT
AGND
LDAC
LDAC
DAC REGISTER
RS RS
WR WR
INPUT REGISTER
RS
D15 D14
D0
Figure 19. 16-Bit AD5547 Equivalent R-2R DAC Circuit with Digital Section, One Channel Shown
Rev. 0 | Page 12 of 20

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