ANALOG DEVICES CN-0183 Service Manual

CN-0183

Rev. 0

engineers. Standard engineering practices have been employed in the design and construction of
each circuit, and their function and performance have been tested and verified in a lab environment at

temperature. However, you are solely responsible for testing the circuit and determining its

suitability and applicability for your use and application. Accordingly, in no event shall Analog Devices

equential or punitive damages due to any cause

whatsoever connected to the use of any Circuits from the Lab circuits. (Continued on last page)

Fax: [phone] ©2012 Analog Devices, Inc. All rights reserved.

+

+

+

+

DAC A

DAC H

V

OUT

A

V

OUT

H

V

REFIN/VREFOUT

GND

V

DD

SYNC
SCLK
DIN
LDAC
CLR

V

S

OUTPUT

GND

1.5kΩ

1.5kΩ

52.3kΩ

SW

100nF

VIN

EN

BST

ADP2300

GND

FB

10kΩ

10kΩ

V

IN

= +12V

+5V

+5V

–5V

+5V

10µF 0.1µF

10µF 0.1µF

1µF

TP2

+2.5V

0V TO +2. 5V

AD8638

L1

L1: COILCRAFT, L P D4012- 472M LB,
COUPLED I NDUCTOR, 4.7µ H

REF192

AD5668

TP1

DAC_OUT

BIPOLAR_OUT

−2.5V TO +2.5V

R2

10kΩ

R1

10kΩ

4.7µF

1µF

10µF

+

10µF

+5V

–5V

09471-001

Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0183.

Precision 16-Bit, Bipolar Output Voltage Source with +12 V to ±5 V Supply

EVALUATION AND DESIGN SUPPORT

Circuit Evaluation Boards

CN-0183 Circuit Evaluation Board (EVAL-CN0183-SDZ)
System Demonstration Platform (EVAL-SDP-CB1Z)

Design and Integration Files

Schematics, Layout Files, Bill of Materials

CIRCUIT FUNCTION AND BENEFITS

The circuit shown in Figure 1 provides a precision 16-bit, low
drift bipolar voltage output of ±2.5 V and operates on a single
+10 V to +15 V supply. The unipolar voltage outputs of the

AD5668 octal denseDAC are amplified and level shifted by the
AD8638 auto-zero op amps. The maximum drift contribution

Circuit Note

Devices Connected/Referenced

16-Bit Voltage Output denseDAC with

AD5668

AD8638 16 V Auto-Zero, Rail-to-Rail Output Op Amp

ADP2300

REF192

of the AD8638 is only 0.06 ppm/°C. The external REF192 reference
ensures a maximum drift of 5 ppm/°C (E grade) and provides a
low impedance pseudo ground for the AD8638 level gain and
shifting circuit.

The circuit offers an efficient solution to a problem often
encountered in systems with a single +12 V supply rail. Proper
printed circuit board (PCB) layout and grounding techniques
ensure that the ADP2300 switching regulator does not degrade
the overall performance of the circuit.

5 ppm/°C On-Chip Reference and SPI
Interface

1.2 A, 20 V, 700 kHz, Nonsynchronous Step­Down Switching Regulator

Precision Micropower, 2.5 V Low Dropout
Voltage Reference

Circuits from the Lab™ circuits from Analog Devices have been designed and built by Analog Devices

room

be liable for direct, indirect, special, incidental, cons

Figure 1. Bipolar Output DAC Circuit with ±5 V Power Supplies

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]

www.analog.com

CN-0183 Circuit Note

6
5
4
3
2
1
0

INL (LSB)

–1
–2
–3
–4
–5

0 10000 20000 30000

DAC CODE

40000 50000 60000

09471-002

0.6

0.4

0.2

0

DNL (LSB)

–0.2

–0.4

–0.8

–0.6

0 10000 20000 30000

DAC CODE

40000 50000 60000

09471-003

8

6

4

2

INL (LSB)

0

–2

–6

–4

0 10000 20000 30000

DAC CODE

40000 50000 60000

09471-004

0.8

0.6

0.4

0.2

0

–0.2

–0.4

DNL (LSB)

–0.6

–0.8

–1.0

0 10000 20000 30000

DAC CODE

40000 50000 60000

09471-005

CIRCUIT DESCRIPTION

The AD5668 is a 16-bit, octal, voltage output denseDAC
controlled by an SPI interface. It contains an on-chip reference
with a 10 ppm/°C maximum drift specification. The on-chip
reference is off at power-up, allowing the use of an external
reference. The internal reference is enabled via a software write.
In the circuit shown in Figure 1, an external REF192 is used
because a low output impedance is required to drive the 2.5 V
pseudo ground reference for the AD8638 op amps.

The output voltage of the AD5668 is 0 V to 2.5 V at TP1, and
this signal drives the noninverting input of the AD8638 op amp.
The signal gain of the op amp is 1 + R2/R1, which is 2 for R1 = R2.
A negative 2.5 V offset is injected into the op amp output by
driving R1 with the 2.5 V reference. The result is a bipolar
output voltage at TP2 that swings from −2.5 V to +2.5 V.

The circuit operates on a single supply voltage of nominally 12 V,
which can vary between 10 V and 15 V. The regulated −5 V
supply rail is developed from an ADP2300 switching regulator
connected in the inverting buck-boost configuration. The circuit
can be designed using the ADIsimPower program available at

www.analog.com/ADIsimPower. The L1 coupled inductor is

used to develop an unregulated 5 V supply for the circuit using
a Zeta configuration. This circuit yields high efficiency for small
output currents.

The integral nonlinearity (INL) and differential nonlinearity
(DNL) measured at TP2 (bipolar output) are shown in Figure 2
and Figure 3, respectively.

The INL and DNL measured at TP1 (unipolar DAC output) are
shown in Figure 4 and Figure 5, respectively.

Figure 3. DNL Performance of Bipolar Output (TP2)

Figure 4. INL Performance of Unipolar DAC Output (TP1)

Figure 2. INL Performance of Bipolar Output (TP2)

Rev. 0 | Page 2 of 5

Figure 5. DNL Performance of Unipolar DAC Output (TP1)