Analog Devices AD570 Datasheet

Complete 8-Bit

a

FEATURES
Complete A/D Converter with Reference and Clock
Fast Successive Approximation Conversion: 25 ms
No Missing Codes Over Temperature

08C to +708C: AD570J

–558C to +1258C: AD570S
Digital Multiplexing: Three-State Outputs
18-Pin Ceramic DIP
Low Cost Monolithic Construction

PRODUCT DESCRIPTION

The AD570 is an 8-bit successive approximation A/D converter
consisting of a DAC, voltage reference, clock, comparator, suc­cessive approximation register and output buffers—all fabricated
on a single chip. No external components are required to per­form a full accuracy 8-bit conversion in 25 µs.

The AD570 incorporates the most advanced integrated circuit
design and processing technology available today. I
grated injection logic) processing in the fabrication of the SAR
function along with laser trimming of the high stability SiCr
thin-film resistor ladder network at the wafer stage (LWT) and a
temperature compensated, subsurface Zener reference insures
full 8-bit accuracy at low cost.

Operating on supplies of +5 V and –15 V, the AD570 accepts
analog inputs of 0 V to +10 V unipolar of ±5 V bipolar, exter­nally selectable. As the BLANK and
low, the three-state outputs go into the high impedance state
and a conversion commences. Upon completion of the conver­sion, the
the output. Pulling the BLANK and
three states the outputs and readies the device for the next con­version. The AD570 executes a true 8-bit conversion with no
missing codes in approximately 25 µs.

The AD570 is available in two version; the AD570J is specified
for the 0°C to +70°C temperature range, the AD570S for –55°C
to +125°C. Both guarantee full 8-bit accuracy and no missing
codes over their respective temperature ranges.

DATA READY line goes low and the data appears at

CONVERT input is driven

CONVERT input high

2

L (inte-

A-to-D Converter

AD570*

FUNCTIONAL BLOCK DIAGRAM

PRODUCT HIGHLIGHTS

1. The AD570 is a complete 8-bit A/D converter. No external
components are required to perform a conversion. Full-scale
calibration accuracy of ±0.8% (2 LSB of 8 bits) is achieved
without external trims.

2. The AD570 is a single chip device employing the most ad­vanced IC processing techniques. Thus, the user has at his
disposal a truly precision component with the reliability and
low cost inherent in monolithic construction,

3. The AD570 accepts either unipolar (0 V to +10 V) or bipolar
(–5 V to +5 V) analog inputs by grounding or opening a
single pin.

4. The device offers true 8-bit accuracy and exhibits no missing
codes over its entire operating temperature range.

5. Operation is guaranteed with –15 V and +5 V supplies. The
device will also operate with a –12 V supply.

6. The AD570S is also available processed to MIL-STD-883C,
Class B. The military data sheet for the AD570SD/883B is
included in the Analog Devices Military Products Databook.

*U.S. Patents Numbered: 3,940,760; 4,213,806 and 4,136,349.

REV. A

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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.

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(TA = +258C, V+ = +5 V, V– = –12 V or –15 V, all voltages measured with respect to

AD570–SPECIFICATIONS

Model Min Typ Max Min Typ Max Units

RESOLUTION
RELATIVE ACCURACY LSB

T

to T

MIN

FULL-SCALE CALIBRATION ±2 ±2 LSB
UNIPOLAR OFFSET 61/2 61/2 LSB
BIPOLAR OFFSET 61/2 61/2 LSB
DIFFERENTIAL NONLINEAIRTY

T

to T

MIN

TEMPERATURE RANGE 0 +70 –55 +125 °C
TEMPERATURE COEFFICIENTS

Unipolar Offset 61 61 LSB
Bipolar Offset 61 61 LSB
Full-Scale Calibration 62 62 LSB

POWER SUPPLY REJECTION

TTL Positive Supply

+4.5 V ≤ V + ≤ +5.5 V 62 62 LSB

Negative Supply

–16.0 V ≤ V – ≤ –13.5 V 62 62 LSB

ANALOG INPUT IMPEDANCE 3.0 5.0 7.0 3.0 5.0 7.0 kΩ
ANALOG INPUT RANGES

Unipolar 0 +10 0 +10 V
Bipolar –5 +5 –5 +5 V

OUTPUT CODING

Unipolar Positive True Binary Positive True Binary
Bipolar Positive True Offset Binary Positive True Offset Binary

LOGIC OUTPUT

Output Sink Current

(V

OUT

Output Source Current

(V

OUT

Output Leakage 640 640 µA

LOGIC INPUTS

Input Current 6100 6100 µA
Logic “1” 2.0 2.0 V
Logic “0” 0.8 0.8 V

CONVERSION TIME 15 25 40 15 25 40 µs
POWER SUPPLY

V+ +4.5 +5.0 +7.0 +4.5 +5.0 +7.0 V
V– –12.0 –15 –16.5 –12.0 –15 –16.5 V

OPERATING CURRENT

V+ 7 10 7 10 mA
V– 9 15 9 15 mA

PACKAGE OPTION

Ceramic

NOTES

1

The AD570 is a selected version of the AD571 10-bit A-to-D converter. Only TTL logic inputs should be connected to Pins 1 and 18 (or no connection made) or
damage may result.

2

For details on grade package offerings for SD-grade in accorance with MIL-STD-883, refer to Analog Devices’ Military Products databook or current /883 data sheet.

Specifications subject to change without notice.
Specifications shown in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min
and max specifications are guaranteed, although only those shown in boldface are tested on all production units.

1

MAX

MAX

= 0.4 V max, T

= 2.4 V max, T

2

MIN

MIN

to T

to T

) 3.2 3.2 mA

MAX

) 0.5 0.5 mA

MAX

DIP (D-18) AD570JD AD570SD

digital common, unless otherwise noted)

AD570J AD570S

8 8 Bits

61/2 61/2 LSB

88 Bits

–2–

REV. A

AD570

ABSOLUTE MAXIMUM RATINGS

V+ to Digital Common . . . . . . . . . . . . . . . . . . . . . 0 V to +7 V

V– to Digital Common . . . . . . . . . . . . . . . . . . 0 V to –16.5 V

Analog Common to Digital Common . . . . . . . . . . . . . . . ±1 V

Analog Input to Analog Common . . . . . . . . . . . . . . . . . ±15 V

Control Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V to V+

Digital Outputs (Blank Mode) . . . . . . . . . . . . . . . . . . 0 V to V+

Power Dissipation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 mW

CIRCUIT DESCRIPTION

The AD570 is a complete 8-bit A/D converter which requires
no external components to provide the complete successive­approximation analog-to-digital conversion function. A block
diagram of the AD570 is shown on last page. Upon receipt of
the

CONVERT command, the internal 8-bit current output

DAC is sequenced by the I

2

L successive-approximation register
(SAR) from its most-significant bit (MSB) to least-significant
bit (LSB) to provide an output current which accurately bal­ances the input signal current through the 5 kΩ input resistor.
The comparator determines whether the addition of each suc­cessively-weighted bit current causes the DAC current sum to
be greater or less than the input current; if the sum is less the bit
is left on, if more, the bit is turned off. After testing all the bits,
the SAR contains a 8-bit binary code which accurately repre­sents the input signal to within ±1/2 LSB (0.20%).

Upon completion of the sequence, the

DATA READY signal
goes low, and the bit output lines become active high or low
depending on the code in the SAR. When the

BLANK and

CONVERT line is brought high, the output buffers again go

“open”, and the SAR is prepared for another conversion cycle.
The temperature compensated buried Zener reference provides

the primary voltage reference to the DAC and guarantees excel­lent stability with both time and temperature. The bipolar offset
input controls a switch which allows the positive bipolar offset
current (exactly equal to the value of the MSB less 1/2 LSB)

BIT 2

0.120

BIT 1
MSB

BLANK

&

CONV

BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 BIT 8

V+

LSB

DATA
READY

signal, an input current will be generated which exactly matches
the DAC output with all bits on. (The input resistor is trimmed
slightly low to facilitate user trimming, as discussed on the next
page.)

POWER SUPPLY SELECTION

The AD570 is designed and specified for optimum performance
using a +5 V and –15 V supply. The supply current drawn by
the device is a function of the operating mode (BLANK or
CONVERT), as given on the specification page. The supply
currents change only moderately over temperature as shown in
Figure 2, and do not change significantly with changes in V–
from –10.8 volts to –16 volts.

Figure 2. AD570 Power Supply Current vs. Temperature

CONNECTING THE AD570 FOR STANDARD OPERATION

The AD570 contains all the active components required to per­form a complete A/D conversion. Thus, for most situations, all
that is necessary is to connect the power supply (+5 V and –15 V),
the analog input, and the conversion start signal. But, there are
some features and special connections which should be consid­ered for achieving optimum performance. The functional pinout
is shown in Figure 3.

DIGITAL
COMMON

BIPOLAR

V–

ANALOG IN

THE AD570 IS ALSO AVAILABLE IN A LASER-TRIMMED PASSIVATED
CHIP FORM. CONSULT CHIP CATALOG FOR APPLICATION PARTICULARS.
FIGURE 3 SHOWS THE CHIP METALLIZATION LAYOUT AND BONDING PADS.

ANALOG COMMON

0.151

OFFSET
CONTROL

Figure 1. Chip Bonding Diagram

to be injected into the summing (+) node of the comparator to
offset the DAC output. Thus the nominal 0 V to +10 V unipo­lar input range becomes a –5 V to +5 V range. The 5 kΩ thin­film input resistor is trimmed so that with a full-scale input

REV. A

–3–

Figure 3. AD570 Pin Connections