ADADC85Z-122 [ADI]
IC 2-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, CDIP32, SIDE BRAZED, CERAMIC, DIP-32, Analog to Digital Converter;
| 型号： | ADADC85Z-122 |
| 厂家： | 
ADI |
| 描述： | IC 2-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, CDIP32, SIDE BRAZED, CERAMIC, DIP-32, Analog to Digital Converter CD 转换器 |
| 文件： | 总12页 (文件大小：1080K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Fast, Complete
12-Bit A/D Converters
AD ADC84/AD ADC85
FEATURES
PERFORMANCE
Complete 12-bit A/D converter with reference and clock
Fast successive approximation conversion: 10 µs or 5 µs
Buried Zener reference for long-term stability and low
Gain TC: 10 ppm/°C
Max nonlinearity: < 0.012ꢀ
Low power: 880 mW typ
Low chip count—high reliability
Industry-standard pinout
Z models for 12 V operation available
MIL-STD-883B processing available
VERSATILITY
Negative true parallel logic outputs
Short cycle capability
Precision +6.3 V reference for external applications
PRODUCT DESCRIPTION
Figure 1. Functional Block Diagram
The AD ADC84/AD ADC85 series devices are high speed, low cost
12-bit successive approximation analog-to-digital converters that
include an internal clock, reference, and comparator. Its hybrid IC
design utilizes MSI digital and linear monolithic chips in
conjunction with a 12-bit monolithic DAC to provide modular
performance and versatility with IC size, price, and reliability.
The AD ADC84 and AD ADC85C are specified for operation over
the ±°C to +7±°C temperature range. The AD ADC85 and
AD ADC85S are specified for the –25°C to +85°C and –55°C to
+125°C ranges, respectively. The serial output function is no longer
supported on the AD ADC84/AD ADC85 after date code 9623.
PRODUCT HIGHLIGHTS
Important performance characteristics of the AD ADC84/
AD ADC85 series include maximum linearity error of ±±.±12ꢀ%
gain TC below 15 ppm/°C at 25°C% typical power dissipation of
88± mW% and conversion time of less than 1± µs for the 12-bit
versions. Of considerable significance in severe and aerospace
applications is the guaranteed performance from –55°C to +125°C
of the AD ADC85S, which is also available with environmental
screening. Monotonic operation of the feedback DAC guarantees
no missing codes over temperature ranges of ±°C to +7±°C, –25°C
to +85°C, and –55°C to +125°C.
1. The AD ADC84/ AD ADC85 series devices are complete
12-bit ADCs. No external components are required to perform
a conversion.
2. The AD ADC84/ AD ADC85 directly replaces other devices of
this type with significant increases in performance.
3. The fast conversion rates of the AD ADC84 and AD ADC85
(1± μs) make them an excellent choice for applications
requiring high system throughput rates.
The design of the AD ADC84/AD ADC85 includes scaling resistors
that provide analog input signal ranges of ±2.5 V, ±5 V, ±1± V, ± V to
+5 V, or ± V to +1± V. The 6.3 V precision reference, which can be
used for external applications, and the input buffer amplifier add
flexibility and value. All digital signals are fully DTL and TTL
compatible, and the data output is negative-true and available in
parallel form.
4. The internal buried Zener reference is laser trimmed to 6.3 V
±±.1ꢀ and ±1± ppm/°C typical TC. The reference is available
externally and can provide up to 1 mA.
5. The integrated package construction provides high quality and
reliability with small size and weight.
6. The monolithic 12-bit feedback DAC is used for reduced chip
count and higher reliability.
The AD ADC84/AD ADC85 are available in a performance grade
specified for 12-bit accuracy (±±.±12ꢀ ꢁSR max) with 1± µs
maximum conversion time.
7. The AD ADC85S/883B comes processed to MIL-STD-883,
Class B requirements.
Rev. B
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
Fax: 781.326.8703
www.analog.com
© 2003 Analog Devices, Inc. All rights reserved.
AD ADC84/AD ADC85
TABLE OF CONTENTS
Specifications..................................................................................... 3
Typical Performance Characteristics ............................................. 5
Functional Description.................................................................... 6
Offset Adjustment ........................................................................ 6
Gain Adjustment........................................................................... 6
Theory of Operation.................................................................... 6
Timing............................................................................................ 6
Digital Output Data ..................................................................... 7
Input Scaling ..................................................................................8
Input Voltage Range and LSB Values ..........................................8
Calibration......................................................................................9
Grounding......................................................................................9
Clock Rate Control Alternate Connections............................ 10
Microprocessor Interfacing....................................................... 10
Outline Dimensions....................................................................... 11
Ordering Guide .......................................................................... 11
REVISION HISTORY
Revision B
11/03—Data Sheet changed from Rev. A to Rev. B
Removed AD5240...............................................................Universal
Updated format...................................................................Universal
Added text to PRODUCT DESCRIPTION .................................. 1
Updated OUTLINE DIMENSIONS ............................................ 11
Rev. B | Page 2 of 12
AD ADC84/AD ADC85
SPECIFICATIONS
Table 1. Typical @ 25°C, 15 V and +5 V, unless otherwise noted
Model
AD ADC84
AD ADC85C AD ADC85
AD ADC85S
Unit
RESOLUTION
12
12
12
12
Bits
ANALOG INPUTS
Voltage Ranges
Bipolar
2.ꢀ5 ꢀ5 1ꢁ
ꢁ to +ꢀ5 ꢁ to +1ꢁ
*
*
*
*
*
*
V
V
Unipolar
Impedance (Direct Input)
ꢁ V to +ꢀ V5 2.ꢀ V
ꢁ V to +1ꢁ V5 ꢀ V
1ꢁ V
2.ꢀ ( 2ꢁ0)
ꢀ ( 2ꢁ0)
1ꢁ ( 2ꢁ0)
*
*
*
*
*
*
*
*
*
kΩ
kΩ
kΩ
Buffer Amplifier1
Impedance (Min)
Bias Current
1ꢁꢁ
ꢀꢁ
*
*
*
*
*
*
MΩ
nA
Settling Time
to ꢁ.ꢁ10 for 2ꢁ V Step
DIGITAL INPUTS2
Convert Command
2
*
*
*
µs
Positive Pulse 1ꢁꢁ ns Min Trailing
Edge Initiates Conversion
1
*
*
*
*
*
*
Logic Loading
TTL Load
0
TRANSFER CHARACTERISTICS ERROR
Gain Error3
ꢁ.1 ( ꢁ.2ꢀ0 maꢂ)
Adjustable to Zero
ꢁ.ꢁꢀ ( ꢁ.20 maꢂ)
ꢁ.1 ( ꢁ.2ꢀ0 maꢂ)
ꢁ.ꢁ12
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
3
Offset Error
Unipolar
Bipolarꢀ
0 of FSR4
0 of FSR
0 of FSR
LSB
Linearity Error (maꢂ)6
Inherent Quantization Error
Differential Linearity Error
No Missing Codes
Temperature Range
Power Supply Sensitivity
1ꢀ V
ꢁ.ꢀ
ꢁ.ꢀ
LSB
ꢁ to +7ꢁ
ꢁ to +7ꢁ
–2ꢀ to +8ꢀ
–ꢀꢀ to +12ꢀ
°C
ꢁ.ꢁꢁ4
ꢁ.ꢁꢁ1
*
*
*
*
*
*
0 of FSR/0 V
0 of FSR/0 V
+ꢀ V
DRIFT
Specification Temperature Range
Gain (Maꢂ)
ꢁ to +7ꢁ
3ꢁ
*
–2ꢀ to +8ꢀ
1ꢀ
–ꢀꢀ to +12ꢀ
2ꢀ
°C
ppm/°C
2ꢀ
Offset
Unipolar
Bipolar (Maꢂ)
Linearity
Monotonicity
3
1ꢀ
3
*
12
*
*
7
2
*
*
ꢀ maꢂ
1ꢁ
ppm/°C
ppm/°C
ppm/°C
5
*
*
*
Guaranteed
1ꢁ
*
CONVERSION SPEED (MAX)
*
µs
Rev. B | Page 3 of 12
AD ADC84/AD ADC85
Model
AD ADC84
AD ADC85C AD ADC85
AD ADC85S
Unit
DIGITAL OUTPUT
(All Codes Complementary)
Parallel
Output Codes7
Unipolar
Bipolar
CSB
COB, CTC
2
Logic 1 during Conversion
2
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
Output Drive
Status
Status Output Drive
Internal Clock
Clock Output Drive
Frequency
TTL Loads
TTL Loads
2
*
*
*
*
*
*
*
*
*
TTL Loads
MHz
V
1.9/1.22
INTERNAL REFERENCE VOLTAGE
6.3/ 1ꢀ mV max
Maximum External Current (with
No Degradation of Specifications)
1.0
*
*
*
mA
Tempco of Drift (Max)
POWER REQUIREMENTS
Rated Voltages
20 max
10 typ
ꢀ typ
ꢀ typ
ppm/°C
+ꢀ, 1ꢀ
+4.7ꢀ to +ꢀ.2ꢀ and
13.ꢀ to ꢁ16.ꢀ
+4.7ꢀ to +ꢀ.2ꢀ and
11.4 to ꢁ16.ꢀ
*
*
*
*
*
*
*
*
*
V
V
V
Range for Rated Accuracy
Z Models8
Supply Drain
+1ꢀ V
ꢁ1ꢀ V
2ꢀ Max
3ꢀ Max
140 Max
1ꢀ00 Max
*
*
*
*
*
*
*
*
*
*
*
*
mA
mA
mA
mW
+ꢀ V
Total Power Dissipation
TEMPERATURE RANGE
Specification
Operating (Derated Specs)
Storage
0 to +70
ꢁ2ꢀ to +8ꢀ
ꢁꢀꢀ to +12ꢀ
*
*
*
ꢁ2ꢀ to +8ꢀ
ꢁꢀꢀ to +12ꢀ
*
ꢁꢀꢀ to +12ꢀ
ꢁꢀꢀ to +12ꢀ
*
°C
°C
°C
PACKAGE OPTION9
DH-32F
Ceramic
Ceramic
Ceramic
Ceramic
*Specifications same as AD ADC84.
1 Buffer settling time adds to conversion speed when buffer is connected to input.
2 DTL/TTL compatible Logic 0 = 0.8 V max, Logic 1 = 2.0 V min for digital output, Logic 0 = 0.4 V max, Logic 1 = 2.4 V min.
3 Adjustable to zero.
4 FSR means full-scale range.
ꢀ Guaranteed at VIN = 0 V.
6 Error shown is the same as 1/2 LSB max error in % of FSR.
7 See Table 2.
8 For 12 V operation, add Z to model number. Input range limited to a maximum of ꢀ V.
9 For package outline information, see Outline Dimensions section.
Rev. B | Page 4 of 12
AD ADC84/AD ADC85
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 4. Change in Differential Linearity vs. Conversion Speed
Figure 2. Linearity Error vs. Conversion Speed
Figure 3. Gain Drift Error (%FSR) vs. Temperature
Figure 5. Conversion Speed vs. Control Voltage
Rev. B | Page ꢀ of 12
AD ADC84/AD ADC85
FUNCTIONAL DESCRIPTION
OFFSET ADJUSTMENT
The zero adjust circuit consists of a potentiometer connected
across ±±S with its slider connected through a 1.8 MΩ resistor
to Comparator Input Pin 22 for all ranges. As shown in Figure 6,
the tolerance of this fixed resistor is not critical, and a carbon
composition type is generally adequate. Using a carbon
An alternate gain adjust circuit which contributes negligible
gain tempco if metal film resistors (Tempco < 100 ppm/°C) are
used is shown in Figure 9.
composition resistor having a –1200 ppm/°C tempco contrib-
utes a worst-case offset tempco of 8 × 244 × 10–6 × 1200 ppm/°C
= 2.3 ppm/°C of FSR, if the OFFSET ADJ potentiometer is set at
either end of its adjustment range. Since the maximum offset
adjustment required is typically no more than ±4 ꢀSB, use of a
carbon composition offset summing resistor typically
Figure 9. Low Tempco Gain Adjustment Circuit
contributes no more than 1 ppm/°C of FSR offset tempco.
THEORY OF OPERATION
On receipt of a CON±ERT START command, the AD ADC84/
AD ADC85 converts the voltage as its analog input into an
equivalent 12-bit binary number. This conversion is
accomplished as follows: The 12-bit successive approximation
register (SAR) has its 12-bit outputs connected both to the
device bit output pins and to the corresponding bit inputs of the
feedback DAC. The analog input is successively compared to the
feedback DAC output, one bit at a time (MSB first, ꢀSB last).
The decision to keep or reject each bit is then made at the
completion of each bit comparison period, depending on the
state of the comparator at that time.
Figure 6. Offset Adjustment Circuit
An alternate offset adjust circuit, which contributes negligible
offset tempco if metal film resistors (tempco <100 ppm/°C) are
used, is shown in Figure 7.
TIMING
The timing diagram is shown in Figure 10. Receipt of a
CON±ERT START signal sets the STATUS flag, indicating
conversion in progress. This, in turn, removes the inhibit
applied to the gated clock, permitting it to run through 13
cycles. All the SAR parallel bits, STATUS flip-flops, and the
gated clock inhibit signal are initialized on the trailing edge of
the CON±ERT START signal. At time t0, Bit 1 is reset and Bit 2
to Bit 12 are set unconditionally. At t1, the Bit 1 decision is made
(keep) and Bit 2 is unconditionally reset. At t2, the Bit 2 decision
is made (keep) and Bit 3 is reset unconditionally. This sequence
continues until the Bit 12 (ꢀSB) decision (keep) is made at t12.
After a 40 ns delay period, the STATUS flag is reset, indicating
that the conversion is complete and that the parallel output data
is valid. Resetting the STATUS flag restores the gated clock
inhibit signal, forcing the clock output to the ꢀogic 0 state.
Figure 7. Low Tempco Zero Adjustment Circuit
In either zero adjust circuit, the fixed resistor connected to Pin
22 should be located close to this pin to keep the pin connection
runs short. (Comparator Input Pin 22 is quite sensitive to
external noise pickup).
GAIN ADJUSTMENT
The gain adjust circuit consists of a potentiometer connected
across ±±S with its slider connected through a 10MΩ resistor to
the Gain Adjust pin 27 as shown in Figure 8.
Corresponding parallel data bits become valid on the same
positive-going clock edge (see Figure 10).
Incorporation of the 40ns delay guarantees that the parallel data
is valid at the ꢀogic 1 to 0 transition of the STATUS flag,
permitting parallel data transfer to be initiated by the trailing
edge of the STATUS signal.
Figure 8. Gain Adjustment Circuit
Rev. B | Page 6 of 12
AD ADC84/AD ADC85
NOTES
1.
THE CONVERT START PULSE WIDTH IS 100ns MIN AND MUST REMAIN LOW DURING A CONVERSION. THE CONVERSION
IS INITIATED BY THE “TRAILING EDGE” OF THE CONVERT COMMAND.
10μs FOR 12 BITS (AD ADC84/AD ADC85).
MSB DECISION.
2.
3.
4.
LSB DECISION 20ns PRIOR TO THE STATUS GOING LOW.
*BIT DECISIONS.
Figure 10. Timing Diagram (Binary Code 011001110110)
DIGITAL OUTPUT DATA
Short Cycle Input
Parallel data from TTL storage registers are in negative true
form. Parallel data coding is complementary binary for unipolar
ranges and either complementary offset binary or
complementary twos complement binary, depending on
whether BIT 1 (Pin 12) or its logical inverse
used as the MSB. Parallel data becomes valid approximately
40 ns before the STATUS flag returns to Logic “0”, permitting
parallel data transfer to be clocked on the “1” to “0” transition of
the STATUS flag.
A short cycle input, Pin 14, permits the timing cycle shown in
Figure 10 to be terminated after any number of desired bits has
been converted, permitting somewhat shorter conversion times
in applications not requiring full 12-bit resolution. When 12-bit
resolution is required, Pin 14 is connected to +5 V (Pin 16).
When 10-bit resolution is required, Pin 14 is connected to Bit 11
output Pin 2. The conversion cycle then terminates, and the
STATUS flag resets after the Bit 10 decision (t10 + 40 ns in
timing diagram of Figure 10). Short cycle pin connections and
associated maximum 12-, 10-, and 8-bit conversion times are
summarized in Table 2.
BIT 1
(Pin 13) is
Parallel data outputs change state on positive-going clock edges.
There are 13 negative-going clock edges in the complete 12-bit
conversion cycle, as shown in Figure 10. The first edge shifts an
invalid bit into the register, which is shifted out on the 13th
negative-going clock edge.
Rev. B | Page 7 of 12
AD ADC84/AD ADC85
INPUT SCALING
The AD ADC84/AD ADC85 inputs should be scaled as close to
the maximum input signal range as possible in order to utilize
the maximum signal resolution of the A/D converter. Connect
the input signal as shown in Table 3. See Figure 11 for circuit
detail.
Figure 11. Input Scaling Circuit
Table 2. Short Cycle Connections
Connect Short Cycle
Pin 14 to Pin
Connect Clock Rate Control
Pin 17 to Pin
Resolution
Bits (% FSR)
AD ADC84/AD ADC85
ConversionTime (μs)
Status Flag
Reset
16
2
4
15
16
28
12
10
8
0.024
0.100
0.390
10 (5)
8.5 (4.1)
6.8 (3.3)
t12 + 40 ns
t10 + 40 ns
t8 + 40 ns
Table 3. Input Scaling Connections
Input Signal Range Output Code Connect Pin 23 to Pin Connect Pin 25 to Input Signal to Pin
For Direct Input Connect Input Pin 30 Connect
Pin 29 to Pin
10 ꢀ
5 ꢀ
2.5 ꢀ
0 ꢀ to +5 ꢀ
0 ꢀ to +10 ꢀ
COB or CTC
COB or CTC
COB or CTC
CSB
22
22
22
26
26
Input Signal
Open
Pin 22
Pin 22
Open
25
24
24
24
24
25
24
24
24
24
CSB
INPUT VOLTAGE RANGE AND LSB VALUES
Table 4. Input Voltages and Code Definition
Analog Input Voltage Range
Code Designation
10 V
5 V
2ꢀ5 V
COB or CTC
5ꢀ
0 V to +10 V
0 V to +5 V
COB1 or CTC2
COB or CTC
CSB3
CSB
One Least Significant Bit (LSB)
FSR
2n
20ꢀ
2n
10ꢀ
2n
10ꢀ
2n
5ꢀ
2n
2n
n = 8
n = 10
n = 12
78.13 mꢀ
19.53 mꢀ
4.88 mꢀ
39.06 mꢀ
9.77 mꢀ
2.44 mꢀ
19.53 mꢀ
4.88 mꢀ
1.22 mꢀ
39.06 mꢀ
9.77 mꢀ
2.44 mꢀ
19.53 mꢀ
4.88 mꢀ
1.22 mꢀ
Transition ꢀalues
MSB
LSB
000 . . . 0004
011 . . . 111
111 . . . 110
+Full Scale
Mid Scale
–Full Scale
+10 ꢀ –3/2 LSB
0
–10 ꢀ +1/2 LSB
+5 ꢀ –3/2 LSB
0
–5 ꢀ +1/2 LSB
+2.5 –3/2 LSB
0
–2.5 ꢀ +1/2 LSB
+10 ꢀ –3/2 LSB
+5 ꢀ
0 ꢀ +1/2 LSB
+5 ꢀ –3/2 LSB
+2.5 ꢀ
0 ꢀ +1/2 LSB
1 COB = Complementary Offset Binary.
2
MSB MSB
).
CTC = Complementary Twos Complement – obtained by using the complement of the most significant bit (
is available to Pin 13.
3 CSB = Complementary Straight Binary.
4 ꢀoltages given are the nominal value for transition to the code specified.
Rev. B | Page 8 of 12
AD ADC84/AD ADC85
–10 V to +10 V Range
CALIBRATION
Set analog input to –9.9951 V; adjust zero for 111111111110
digital output (complementary offset binary) code. Set analog
input to +9.9902 V; adjust Gain for 000000000001 digital output
(complementary offset binary) code. Half-scale calibration
check: set input to 0.0000V; digital output (complementary
offset binary) code should be 011111111111.
External ZERO ADJ and GAIN ADJ potentiometers, connected
as shown in Figure 12 and Figure 13, are used for device
calibration. To prevent interaction of these two adjustments,
zero is always adjusted first and then gain. Zero is adjusted with
the analog input near the most negative end of the analog range
(0 for unipolar and –FS for bipolar input ranges). Gain is
adjusted with the analog input near the most positive end of the
analog range.
Other Ranges
Representative digital coding for 0 to +10 V and –10 V to +10 V
ranges is given above. Coding relationships and calibration
points for 0 to +5 V, –2.5 V to +2.5 V, and –5 V to +5 V ranges
can be found by halving the corresponding code equivalents
listed for the 0 to +10 V and –10 V to +10 V ranges, respectively.
Zero and full-scale calibration can be accomplished to a
precision of approximately ±± LSB using the static adjustment
procedure described above. By summing a small sine or
triangular-wave voltage with the signal applied to the analog
input, the output can be cycled through each of the calibration
codes of interest to more accurately determine the center (or
end points) of each discrete quantization level.
GROUNDING
Many data acquisition components have two or more ground
pins which are not connected together within the device. These
grounds are usually referred to as the Logic Power Return,
Analog Common (Analog Power return), and Analog Signal
Ground. These grounds must be tied together at one point,
usually at the system power-supply ground. Ideally, a single
solid ground would be desirable. However, since current flows
through the ground wires and etch stripes of the circuit cards,
and since these paths have resistance and inductance, hundreds
of millivolts can be generated between the system ground point
and the ground pin of the AD ADC84/ AD ADC85. Separate
ground returns should be provided to minimize the current
flow in the path from sensitive points to the system ground
point. In this way, supply currents and logic-gate return currents
are not summed into the same return path as analog signals
where they would cause measurement errors.
Figure 12. Analog and Power Connections for
Unipolar 0 to +10 V Input Range with Buffer Follower
Figure 13. Analog and Power Connections for
Bipolar –10 V to +10 V Input Range with Buffer Follower
Each of the AD ADC84/ AD ADC 85 supply terminals should
be capacitively decoupled as close to the device as possible. A
large value capacitor such as 1 µF in parallel with a 0.1 µF
capacitor is usually sufficient. Analog supplies are bypassed to
the Analog Power Return pin and the logic supply is bypassed
to the Logic Power Return pin.
0 to +10 V Range
Set analog input to +1 LSB = +0.0024V. Adjust Zero for digital
output = 111111111110. Zero is now calibrated. Set analog input
to +FSR – 2 LSB = +9.9952V. Adjust gain for 000000000001
digital output code; full-scale (gain) is now calibrated. Half-
scale calibration check: set analog input to +5.0000 V; digital
output code should be 011111111111.
Rev. B | Page 9 of 12
AD ADC84/AD ADC85
significant bits in one byte and the 4 LSBs in the high nibble of
another byte. The data now represents the fractional binary
number relating the analog signal to the full-scale voltage. An
advantage to this organization is that the most-significant eight
bits can be read by the processor as a coarse indication of the
true signal value. The full ±2-bit word can then be read only
when all ±2 bits are needed. This allows faster and more
efficient control of a process.
CLOCK RATE CONTROL ALTERNATE
CONNECTIONS
If adjustment of the CLOCK RATE is desired for faster conver-
sion speeds, the CLOCK RATE CONTROL may be connected
to an external multiturn trim potentiometer with a TCR of
±±11 ppm/°C or less as shown in Figure ±4 and Figure ±5. If the
potentiometer is connected to –±5 V, conversion time can be
increased as shown in Figure 5. If these adjustments are used,
delete the connections shown in Table 2 for Pin ±7. See Figure 2
for nonlinearity error versus conversion speed and Figure 5 for
the effect of the control voltage on clock speed.
Figure ±6 shows a typical connection of 8185-type bus, using a
left-justified data format for unipolar inputs. Status polling is
optional, and can be read simultaneously with the 4LSBs. If it is
desired to right-justify the data, pins ± through ±2 of the
ADADC84/AD ADC85 should be reversed, as well as the
connections to the data bus high and low byte address signals.
When dealing with bipolar inputs (±5V, ±±1V ranges), using the
MSB directly yields a complementary offset binary-coded
output. If complementary twos complement coding is desired, it
Figure 14. 12-Bit Clock Rate Control Optional Fine Adjust
MSB
can be produced be substituting
(Pin ±3) for the MSB.
This facilitates the arithmetic operation which are subsequently
performed on the ADC output data.
Figure 15. 8-Bit Clock Rate Control Optional Fine Adjust
MICROPROCESSOR INTERFACING
The fast conversion times of the AD ADC84/AD ADC85
suggests several methods of interface to microprocessors. In
systems where the ADC is used for high sampling rates on a
single signal which is to be digitally processed, CPU-controlled
conversion may be inefficient due to the slow cycle times of
most microprocessors. It is generally preferable to perform
conversions independently, inserting the resultant digital data
directly into memory. This can be done using direct memory
access (DMA), which is totally transparent to the CPU. Interface
to user-designed DMA hardware is facilitated by the guaranteed
data validity on the falling edge of the EOC signal.
Clearly, ±2 bits of data must be broken up for interface to a 8-bit
wide data bus. There are two possible formats: right-justified
and left-justified. In a right-justified system, the least significant
8 bits occupy one byte and the four MSBs reside in the low
nibble of another byte. This format is useful when the data from
the ADC is being treated as a binary number between 1 and
4195. The left-justified format supplies the eight most-
Figure 16. AD ADC84/AD ADC85 – 8085A Interface Connections
Rev. B | Page 10 of 12
AD ADC84/AD ADC85
OUTLINE DIMENSIONS
0.080 (2.03) MAX
ALL FOUR CORNERS
0.005 (0.13) MIN
ALL FOUR CORNERS
17
32
1
16
0.905 (22.99)
0.880 (22.35)
1.640 (41.66)
1.584 (40.64)
PIN 1
0.230 (5.84)
MAX
0.060 (1.52)
0.040 (1.02)
0.012 (0.31)
0.009 (0.23)
0.910 (23.11)
0.890 (22.61)
0.180 (4.57)
MIN
0.120 (3.05)
MIN
0.020 (0.51)
0.016 (0.41)
0.100 (2.54) 0.055 (1.39)
BSC
0.045 (1.14)
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
Figure 17. 32-Lead Side Brazed Ceramic DIP [SBDIP/H]
(DH-32F)
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
ORDERING GUIDE
Model1
Operation Voltage (V)
Linearity (%)
±0.012
±0.012
±0.012
±0.012
±0.012
±0.012
±0.012
±0.012
±0.012
Temperature Range
0°C to +70°C
0°C to +70°C
Gain TC (ppm/°C)
Conversion Time (µs)
ADADC84-122
ADADC84Z-122
ADADC8ꢀC-122
ADADC8ꢀ-12
ADADC8ꢀZ-122
ADADC8ꢀS-12
ADADC8ꢀSZ-12
ADADC8ꢀS12/88±B
ADADC8ꢀSZ12/88±
±1ꢀ
±12
±1ꢀ
±1ꢀ
±12
±1ꢀ
±12
±1ꢀ
±12
±±0
±±0
±2ꢀ
±1ꢀ
±1ꢀ
±2ꢀ
±2ꢀ
±2ꢀ
±2ꢀ
10
10
10
10
10
10
10
10
10
0°C to +70°C
–2ꢀ°C to +8ꢀ°C
–2ꢀ°C to +8ꢀ°C
–ꢀꢀ°C to +12ꢀ°C
–ꢀꢀ°C to +12ꢀ°C
–ꢀꢀ°C to +12ꢀ°C
–ꢀꢀ°C to +12ꢀ°C
1 For complete model number, suffixes must be added for “Z” option (±12 V operation), linearity. The following guide shows the proper suffix order:
AD ADC(*)(**)-(***), where * = Model Number, ** = Z Version Designator, and *** = Linearity.
Typical Part Numbers: AD ADC84-12, AD ADC8ꢀSZ-12.
2 Last Time Buy.
Rev. B | Page 11 of 12
AD ADC84/AD ADC85
NOTES
© 2003 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
C03262–0–11/03(B)
Rev. B | Page 12 of 12
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