Datasheet AD7886JD, AD7886BD, AD7886TD, AD7886KP, AD7886KD Datasheet (Analog Devices)

LC2MOS

a

12-Bit, 750 kHz/1 MHz, Sampling ADC

FEATURES
750 kHz/1 MHz Throughput Rate
1 ms/750 ns Conversion Time
12-Bit No Missed Codes Over Temperature
67 dB SNR at 100 kHz Input Frequency
Low Power—250 mW typ
Fast Bus Access Time—57 ns max

APPLICATIONS
Digital Signal Processing
Speech Recognition and Synthesis
Spectrum Analysis
DSP Servo Control

GENERAL DESCRIPTION

The AD7886 is a 12-bit ADC with a sample-and-hold amplifier
offering high speed performance combined with low power dissi­pation. The AD7886 is a triple pass flash ADC that uses 15
comparators in a 4-bit flash technique to achieve 12-bit accuracy
in 1 µs/750 ns conversion time. An on-chip clock oscillator pro-
vides the appropriate timing for each of the three conversion
stages, eliminating the need for any external clocks. Acquisition
time of the sample-and-hold amplifier gives a resulting through­put rate of 750 kHz/1 MHz.*

The AD7886 operates from ±5 V power supplies. Pin-strappable
inputs offer a choice of three analog input ranges: 0 V to 5 V,
0 V to 10 V or ±5 V.

In addition to the traditional dc accuracy specifications such as
linearity, offset and full-scale errors, the AD7886 is also speci­fied for dynamic performance parameters, including harmonic
distortion and signal-to-noise ratio.

The AD7886 has a high speed digital interface with three-state
data outputs. Conversion control is provided by a
put. Data access is controlled by

CS and RD inputs, standard

CONVST in-

microprocessor signals. The data access time of less than 57 ns
means that the AD7886 can interface directly to most modern
microprocessors, including DSP processors.

*Contact your local salesperson for further information on the 1 MHz

version.

AD7886

FUNCTIONAL BLOCK DIAGRAM

V

DD

R3

R4

R1
9k

R2

6.3k

4096

RESISTOR

DAC

R5

OSCILLATOR

–
+

AND TIMER

T/H

COMPARATORS

4-BIT FLASH

SEGMENT SELECT

CLOCK

15

AND

LOGIC

VIN1

VIN2

+5REF

SUM

V

REF

AGND

10k 3.5k

10k

The AD7886 is fabricated in Analog Devices’ Linear Com­patible CMOS process, a mixed technology process that
combines precision bipolar circuits with low power CMOS
logic.

The AD7886 is available in both a 28-pin DIP and a 28-pin
leaded chip carrier.

PRODUCT HIGHLIGHTS

1. Fast 1.33 µs/1 µs Throughput Time.

Fast throughput time makes the AD7886 suitable for a
wide range of data acquisition applications.

2. Dynamic Specifications for DSP Users.
The AD7886 is specified for ac parameters, including
signal-to-noise ratio, harmonic distortion and inter­modulation distortion. Key digital timing parameters are
also tested and guaranteed over the full operating tem­perature range.

3. Fast Microprocessor Interface.
Standard control signals,

CS and RD, and fast bus ac­cess times make the AD7886 easy to interface to micro­processors.

4. Low Power.

2

LC

MOS fabrication process gives low power dissipa-

tion of 250 mW.

CS RD CONVST

CONTROL

TIMER

4-BIT

LATCH

4-BIT

LATCH

4-BIT

LATCH

THREE
STATE

OUTPUTS

AD7886

V

DGND

SS

BUSY

DB11

DB0

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

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] World Wide Web Site: http://www.analog.com
Fax: [phone] © Analog Devices, Inc., 1997

AD7886–SPECIFICATIONS

as shown in Figure 2. All Specifications T

MIN

to T

unless otherwise noted. Specifications apply for 750 kHz version.)

MAX

(VDD = +5 V 6 5%, VSS = –5 V 6 5%, A6ND = DGND = O V, V

= –3.5 V, connected

REF

Parameter J Version1K, B Versions1T Version1Units Test Conditions/Comments

DYNAMIC PERFORMANCE

Signal-to-Noise Ratio3 (SNR) 65 67 65 dB min VIN = 100 kHz Sine Wave, f
Total Harmonic Distortion (THD) –75 –75 –75 dB typ VIN = 100 kHz Sine Wave, f
Peak Harmonic or Spurious Noise –77 –77 –77 dB typ VIN = 100 kHz Sine Wave, f

2

SAMPLE

SAMPLE

SAMPLE

Intermodulation Distortion (IMD)
Second Order Terms –80 –80 –80 dB typ fa = 96 kHz, fb = 103 kHz, f

SAMPLE

= 750 kHz

Third Order Terms –80 –80 –80 dB typ

ACCURACY

Resolution 12 12 12 Bits
Integral Linearity T

MIN

to T

MAX

±2 ±2 LSB max

Minimum Resolution for Which

No Missing Codes Are Guaranteed 12 12 12 Bits

Unipolar Offset Error @ +25°C ±5 ±5 ±5 LSB max Input Range: 0 V to 5 V or 0 V to 10 V

T

MIN

to T

MAX

±5 ±5 ±5 LSB max

Bipolar Offset Error @ +25°C ±5 ±5 ±5 LSB max Input Range: ± 5 V

T

MIN

to T

MAX

±5 ±5 ±5 LSB max

Unipolar Gain Error @ +25°C ±5 ±5 ±5 LSB max Input Range: 0 V to 5 V or 0 V to 10 V

T

MIN

to T

MAX

±5 ±5 ±5 LSB max

Bipolar Gain Error @ +25°C ±5 ±5 ±5 LSB max Input Range: ± 5 V

T

MIN

to T

MAX

±5+5 ±5 LSB max

ANALOG INPUT

Unipolar Input Current 1.5 1.5 1.5 mA max Input Ranges: 0 V to 5 V or 0 V to 10 V
Bipolar Input Current ±0.75 ±0.75 ±0.75 mA max Input Range: ±5 V

= 750 kHz
= 750 kHz
= 750 kHz

REFERENCE INPUT

V

REF

–3.5 –3.5 –3.5 Volts ± 2% For Specified Performance

Input Reference Current –10 –10 –10 mA max
R1, Resistance 9 9 9 kΩ nom ±25%
R2, Resistance 6.3 6.3 6.3 kΩ nom ±25%
R2/R1 Ratio 0.7 0.7 0.7 nom ±0.1%

POWER SUPPLY REJECTION

VDD Only, (FS Change) 0.5 0.5 0.5 LSB typ VSS = –5 V, VDD = +4.75 V to +5.25 V
VSS Only, (FS Change) 0.5 0.5 0.5 LSB typ VDD = +5 V, VSS = –4.75 V to –5.25 V

LOGIC INPUTS

Input High Voltage, V
Input Low Voltage, V
Input Current, I
Input Capacitance, C

INH

INL

IN

4

IN

LOGIC OUTPUTS

DB11–DB0, BUSY

Output High Voltage, V
Output Low Voltage, V

OH

OL

DB11–DB0

Floating-State Leakage Current ±10 ±10 ±10 pA max
Floating-State Output Capacitance415 15 15 pF max

POWER REQUIREMENTS

V

DD

V

SS

I

DD

I

SS

Power Dissipation 250 250 250 mW typ CONVST = CS = RD = V

NOTES

I

Temperature ranges are as follows: J, K Versions: 0°C to +70°C; B Version: –40°C to +85°C; T Version: –55°C to + 125°C.

2

Applies to all three input ranges, VIN = 0 to FS, pk-to-pk V.

3

SNR calculation includes distortion and noise components.

4

Sample tested @ +25°C to ensure compliance.

Specifications subject to change without notice.

2.4 2.4 2.4 V min VDD = 5 V ± 5%

0.8 0.8 0.8 V max VDD = 5 V ± 5%
±10 ±10 ±10 µA max VIN = 0 V to V

DD

10 10 10 pF max

4 4 4 V min I

0.4 0.4 0.4 V max I

SOURCE

= 1.6 mA

SINK

= 200 µA

+5 +5 +5 V nom ±5% for Specified Performance
–5 –5 –5 V nom ±5% for Specified Performance
35 35 35 mA max Typically 25 mA, CONVST = CS = RD = V
–35 –35 –35 mA max Typically 25 mA, CONVST = CS = RD = V

350 350 350 mW max

DD

DD

DD

–2–

REV. B

1

WARNING!

ESD SENSITIVE DEVICE

TIMING CHARACTERISTICS

(VDD = +5 V 6 5%, VSS = –5 V 6 5%, AGND = DGND = 0 V)

Limit at Limit at Limit at
T

MIN

, T

MAX

T

MIN

, T

MAX

T

, T

MIN

MAX

Parameter (J, K Versions) (B Version) (T Version) Units Conditions/Comments

AD7886

t

1

50 50 50 ns min CONVST Pulse Width
1 1 1 Fs max

t

2

t

3

t

4

t

5

t

6

3

t

7

0 0 0 ns min CS to RD Setup Time
0 0 0 ns min CS to RD Hold Time
60 60 75 ns min RD Pulse Width
100 100 100 ns max CONVST to BUSY Propagation Delay, (CL = 10 pF)

57 57 70 ns max Data Access Time After RD
10 10 10 ns min Bus Relinquish Time After RD
50 50 60 ns max

t

8

3

t

9

20 20 14 ns min Data Setup Time Prior to BUSY, (CL = 20 pF)
10 10 0 ns min Data Setup Time Prior to

BUSY, (CL = 100 pF)
10 10 10 ns min Bus Relinquish Time After CONVST
100 100 100 ns max

t

10

t

11

t

12

t

13

t

CONV

0 0 0 ns min CS High to CONVST Low
0 0 0 ns min BUSY High to RD Low
250 250 250 ns typ BUSY High to CONVST Low, SHA Acquisition Time

1.333 1.333 1.333 µs min Sampling Interval
950 950 950 ns typ Conversion Time
1000 1000 1000 ns max

NOTES

1

Timing specifications in bold print are 100% production tested. All other times are sample tested at +25°C to ensure compliance. All input signals are specified with tr =
tf = 5 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V.

2

t6 is measured with the load circuit of Figure 1 and defined as the time required for an output to cross 0.8 V or 2.4 V.

3

t7 and t9 are derived from the measured time taken by the data outputs to change by 0.5 V when loaded with the circuit of Figure 1. The measured number is then extrapo­lated back to remove the effects of charging or discharging the load capacitor, C
relinquish times of the part and as such are independent of external bus loading capacitances.

Specifications subject to change without notice.

. This means that the times, t7 and t9, quoted in the timing characteristics are the true bus

L

Figure 1. Load Circuit for Bus Access and Relinquish Time

ABSOLUTE MAXIMUM RATINGS

(T
V

DD

V

SS

AGND to DGND . . . . . . . . . . . . . . . . . –0.3 V to V

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 the AD7886 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.

REV. B

I

OL

TO OUTPUT

PIN

= +25°C unless otherwise noted)

A

C

L

1, 2

I

OH

+2.1V

to AGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V

to AGND . . . . . . . . . . . . . . . . . . . . . . . . . +0.3 V to –7 V

+0.3 V

DD

VIN1, VIN2, SUM, +5REF to AGND . . . . . . –15 V to +15 V

V

to AGND . . . . . . . . . . . . . . . . VSS –0.3 V to V

REF

DD

+0.3 V

Digital Inputs to DGND

CS, RD, CONVST . . . . . . . . . . . . . . –0.3 V to V

+0.3 V

DD

Digital Outputs to DGND

DB0 to DB11, BUSY . . . . . . . . . . . . . –0.3 V to V

+0.3 V

DD

Operating Temperature Range

Commercial (J, K Versions) . . . . . . . . . . . . . . 0°C to +70°C

Industrial (B Version) . . . . . . . . . . . . . . . . –40°C to +85°C

Extended (T Version) . . . . . . . . . . . . . . . –55°C to +125°C

Storage Temperature Range . . . . . . . . . . . .–65°C to + 150°C

Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . .+300°C

Power Dissipation (Any Package) to +75°C . . . . . . 1000 mW

Derates above +75°C by . . . . . . . . . . . . . . . . . . . . 10 mW/°C

NOTES

1

Stresses above those listed under “Absolute Maximum Ratings” may cause
permanent damage to the device. This is a stress rating only; functional operation
of the device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.

2

If VSS is open circuited with VDD and AGND applied, the VSS pin will be pulled
positive, exceeding the Absolute Maximum Ratings. If this possibility exists, a
Schottky diode from VSS to DGND (cathode end to GND) ensures that the

–3–

AD7886

ORDERING GUIDE

Integral

1, 2

Model

AD7886JD 0°C to +70°C 65 D-28
AD7886KD 0°C to +70°C67±2.0 D-28
AD7886JP 0°C to +70°C 65 P-28A
AD7886KP 0°C to +70°C67±2.0 P-28A
AD7886BD –40°C to +85°C67 ±2.0 D-28
AD7886TD –55°C to +125°C65 ±2.0 D-28

NOTES
1Contact your sales office for availability of AD7886BD, AD7886TD and 1 MHz version.

2

Analog Devices reserves the right to ship J-Leaded Ceramic Chip Carrier (JLCCC) in lieu of PLCC packages.

3

D = Ceramic DIP; P = Plastic Leaded Chip Carrier.

DIP Pin
Number Mnemonic Description

Power Supply

10 & 19 V
15 & 24 V

DD

SS

Positive Power Supply, +5 V ± 5%. Both V
Negative Power Supply, –5 V ± 5%. Both V

16 & 23 AGND Analog Ground. Both AGND pins must be tied together.
5 DGND Digital Ground.

Temperature SNR Nonlinearity Package
Range (dBs) (LSBs) Option

PIN FUNCTION DESCRIPTION

pins must be tied together.

DD

pins must be tied together.

SS

3

2
2

Analog and Reference Inputs

17 & 18 VIN Analog Inputs, VIN1 and VIN2. The part can be pin strapped for any one of three analog input ranges;

Range Pin Strap Signal Input

0 V to 5 V Connect VIN2 to VIN1 VIN1 & VIN2
0 V to 10 V Connect VIN2 to GND VIN1
±5 V Connect VIN2 to +5 V VIN1

20 +5REF +5 V Reference input. This input is used in conjunction with SUM and V

inputs to scale an external

REF

+5 V reference to –3.5 V, the required reference for the part (see Figure 2).

21 SUM Summing Point. This input is used in conjunction with +5REF and V

inputs to scale an external

REF

+5 V reference to –3.5 V, the required reference for the part (see Figure 2).

22 V

REF

Voltage Reference Input. The AD7886 is specified with V

REF

= –3.5 V.

Interface and Control

1–4, DB7–DB4 Three-state data outputs.
6–9, DB3–DB0 These outputs are controlled by

CS and RD. DB11 is the Most Significant Bit (MSB).
25–28 DB11–DB8
11
12
13

BUSY BUSY Output indicates converter status. BUSY is low during conversion.
CS Chip Select Input. The device is selected when this input is low.
RD Read Input. This active low signal, in conjunction with CS, is used to enable the output data three-state

drivers.

14 CONVST Conversion Start Input. This input is used to start conversion.

–4–

REV. B

PIN CONFIGURATIONS

AGND

VIN1

VIN2

DB4

DB5

DB6

DB11

DB10

DB9

DB8

DB7

AGND

SUM
+5REF

DB2
DB1
DB0

DGND

DB3

V

SS

V

REF

V

DD

CS

RD

CONVST

V

SS

V

DD

BUSY

AD7886

TOP VIEW

(Not to Scale)

5
6

7
8
9

10
11

28 27 2612

3

4

25
24
23
22

21
20

19

12

13 14 15 16 17 18

AD7886

DIP

DB7
DB6
DB5
DB4

DGND

DB3
DB2
DB1
DB0
V

DD

BUSY

CS

RD

CONVST

1
2
3
4
5
6
7
8
9

10

11
12
13
14

AD7886

TOP VIEW

(Not to Scale)

28
27
26
25
24
23
22
21
20
19
18
17
16
15

DB8
DB9
DB10
DB11
V

SS

AGND
V

REF

SUM
+5REF
V

DD

VIN2
VIN1
AGND
V

SS

TERMINOLOGY

Unipolar Offset Error

The ideal first code transition should occur when the analog
input is 1 LSB above AGND. The deviation of the actual transi­tion from that point is termed the offset error.

Bipolar Zero Error

The ideal midscale transition (i.e., 0111 1111 1111 to 1000
0000 0000) for the +5 V range should occur when the analog
input is at zero volts. Bipolar zero error is the deviation of the
actual transition from that point.

Gain Error

In the unipolar mode, gain error is measured with respect to the
first and last code transition points. The ideal difference be­tween these points is FS–2 LSBs. For bipolar applications, the
gain error is measured from the midscale transition to both the
first and last code transitions. The ideal difference in this case is
FS/2–1 LSB. The gain error is defined as the deviation between
the ideal difference, given above, and the measured difference.
For the bipolar case, there are two gain errors; the figure in the
specification page represents the worst case. Ideal FS depends
on the +5REF input; for the 0 V to 5 V input, ideal FS = +5REF
and for the 0 V to 10 V and +5 V ranges, ideal FS = 2 × + 5REF.

CONVERTER DETAILS

The AD7886 is a triple-pass flash ADC that uses 15 compara­tors in a 4-bit flash technique to perform the 12-bit conversion
procedure. Each of the 4096 quantization levels is realized inter­nally with a precision resistor DAC.

The fifteen comparators first compare the analog input voltage
to the V
four most significant bits and selects 1 out of 16 voltage seg­ments. The comparators are then switched to 15 subvoltages on
that segment to determine the next four bits and select 1 out of

/16 voltages of the resistor array. This determines the

REF

256 voltage segments. A further switching of the comparators to
another 15 subvoltages produces the complete 12-bit conversion

REV. B

PLCC

result. The 12 bits of data are then stored internally in a three­state output latch.

REFERENCE INPUT

The AD7886 operates from a 3.5 V reference, which must be
provided at the V

input. Two on-chip resistors for use with

REF

an external amplifier can be used for deriving 3.5 V from stan­dard 5 V references. Figure 2 shows an example with the AD586
which a is a high performance voltage reference exhibiting
excellent stability performance, 5 ppm/°C max. The external
amplifier serves a second function of force/sensing the V

REF

input. Force/sensing minimizes error contributions from

+V

+V

AD586

GND

IN

+5V

V

OUT

AD707

–

–3.5V

+5REF

SUM

V

REF

R1
9k

R2

6.3k

AD7886*

+

TO DAC

C1

10µF

C2

0.1µF

AGND

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 2. Typical Reference Circuitry

–5–

AD7886

this amplifier typically by 20 MHz which is much greater than
the Nyquist limit of the ADC; as a result, it can be used for
undersampling applications. The track-and-hold amplifier ac­quires the input signal to 12-bit accuracy in less than 333 ns.
The overall throughput time is equal to the conversion time
plus the track/ hold amplifier acquisition time, which is 1.333 µs
for the AD7886.

The operation of the track/hold amplifier is essentially transpar­ent to the user. The track-to-hold transition occurs at the start
of conversion on the falling edge of
procedure does not start until the rising edge of
width of the

CONVST pulse low time determines the track-to
hold settling time. The track/hold reverts back to the track
mode at the end of conversion when

0 TO 5V ANALOG INPUT RANGE

CONVST. The conversion

CONVST. The

BUSY has returned high.

3.5k

+V

+V

IN

V

AD586

GND

OUT

+

5V

AIN

0 TO 5V

OR

0 TO 10V

AD707

–
+

+

5V

V

VIN1

VIN2**

AGND

DD

AD7886*

+

5REF

SUM

–

3.5V
V

REF

10k

0 TO 5V

0 TO 10V

±5V

+5V

VIN1

10k

VIN2

0 TO 10V ANALOG INPUT RANGE

10k

VIN1

10k

VIN2

±5V ANALOG INPUT RANGE

10k

VIN1

10k

VIN2

–

+

3.5k

TO

COMPARATORS

–

+

3.5k

TO

COMPARATORS

–

+

TO

COMPARATORS

Figure 3. Analog Input Range Configurations

ANALOG INPUT RANGES

The AD7886 has three user selectable analog input ranges: 0 V
to 5 V, 0 V to 10 V and ±5 V. Figure 3 shows how to configure
the two analog inputs (VIN1 and VIN2) for these ranges.

UNIPOLAR OPERATION

Figure 4 shows a typical unipolar circuit for the AD7886. The
ideal input/output characteristic is shown in Figure 5. The
designed code transitions occur on integer multiples of 1 LSB.

The output code is natural binary with 1 LSB = FS/4096. FS is
either +5 V or +10 V, depending on how the analog inputs are
configured.

V

C1

10µF

*ADDITIONAL PINS OMITTED FOR CLARITY
**0 TO 5V RANGE: CONNECT VIN2 TO VIN1
0 TO 10V RANGE: CONNECT VIN2 TO AGND

C2

0.1µF

SS

–

5V

Figure 4. Unipolar Operation

OUTPUT

CODE

11...111

11...110

11...101

11...100
FS

4096

00...011

1LSB =

00...010

00...001

00...000

123

FS

VIN, INPUT VOLTAGE (LSBS)

FS – 1LSB

Figure 5. Ideal Input/Output Transfer Characteristic for
Unipolar Operation

–6–

REV. B

AD7886

OFFSET AND GAIN ADJUSTMENT

In most digital signal processing (DSP) applications, offset and
full-scale errors have little or no effect on system performance.
Offset error can usually be eliminated in the analog domain by
ac coupling. Full-scale errors do not cause problems as long as
the input signal is within the full dynamic range of the ADC.
For applications requiring that the input signal range match the
full analog input dynamic range of the ADC, offset and full­scale errors must be adjusted to zero.

UNIPOLAR OFFSET AND GAIN ERROR ADJUSTMENT

If absolute accuracy is an application requirement, offset and
gain can be adjusted to zero. Offset error must be adjusted be­fore gain error. Zero offset is achieved by adjusting the offset of
the op amp driving the analog input (i.e., A1 in Figure 6). For
zero offset error, apply a voltage of 1 LSB to AIN and adjust
the op amp offset until the ADC output code flickers between
0000 0000 0000 and 0000 0000 0001.

0 V to 5 V Range: 1 LSB = 1.22 mV
0 V to 10 V Range: 1 LSB = 2.44 mV

For zero gain, error apply an analog input voltage equal to
FS–1 LSB (last code transition) at AIN and adjust R3 until the
ADC output code flickers between 1111 1111 1110 and 1111
1111 1111.

0 V to 5 V Range: FS–1 LSB = 4.99878 V
0 V to 10 V Range: FS–1 LSB = 9.99756 V

+

5REF

5V

V

DD

AIN

0 TO 5V

OR

0 TO 10V

+V

+V

IN

V

AD586

GND

OUT

AD845

+

A1

VIN1

–

VIN2**

AGND

5V+

R1
82k

+

SUM

AD707

R3

5k

–

–
+

3.5V
V

REF

AD7886*

R2

56k

*ADDITIONAL PINS OMITTED FOR CLARITY
**0 TO 5V RANGE: CONNECT VIN2 TO VIN1
0 TO 10V RANGE: CONNECT VIN2 TO AGND

C1

10µF

C2

0.1µF

V

SS

–

5V

Figure 6. Unipolar Operation with Gain Error Adjust

BIPOLAR OPERATION

Bipolar operation is achieved by providing a +10 V span on
the VIN1 input while offsetting the VIN2 input by +5 V. A
typical circuit is shown in Figure 7. The output code is off­set binary. The ideal input/output transfer characteristic is
shown in Figure 8. The LSB size is (10/4096) V = 2.44 mV.

+

5V

V

DD

+V

+V

AIN

±

5V

IN

+

5V

V

OUT

VIN1

VIN2

AGND

+

5REF

AD586

GND

AD707

–
+

C1

10µF

*ADDITIONAL PINS OMITTED FOR CLARITY

C2

0.1µF

–

3.5V

SUM

AD7886*

V

REF

V

SS

–

5V

Figure 7. Bipolar Operation

OUTPUT

CODE

11...111

11...110

11...101

10...010

10...001

10...000

01...111

01...110

01...101

00...001

00...000

–

FS

2

+1LSB

1LSB–

+1LSB

FS = 10V

1LSB =

VIN, INPUT VOLTAGE – LSBs

+

FS

2

FS

4096

– 1LSB

Figure 8. Ideal Input/Output Characteristics for
Bipolar Operation

REV. B

–7–

AD7886

BIPOLAR OFFSET AND GAIN ADJUSTMENT

In applications where absolute accuracy is important, offset and
gain error can be adjusted to zero. Offset is adjusted by trim­ming the voltage at the VIN1 or VIN2 input when the analog in­put is at zero volts. This can be achieved by adjusting the offset
of an external amplifier used to drive either of these inputs (see
A1 in Figure 9). The trim procedure is as follows:

Apply zero volts at AIN and adjust the offset of A1 until the
ADC output code flickers between 0111 1111 1111 and 1000
0000 0000.

Gain error can be adjusted at either the first code transition
(ADC negative full scale) or the last code transition (ADC posi­tive full scale). Adjusting the reference, as in Figure 9, will trim
the positive gain error only. The trim procedure is as follows:

Apply a voltage of 4.99756 V, (FS/2–1 LSB) at AIN and
adjust R3 until the output code flickers between 1111 1111
1110 and 1111 11111111.

If the first code transition needs adjusting, a gain trim must be
included in the analog signal path. The trim procedure will then
consist of applying an analog signal of –4.99756 V (–FS/2+1 LSB)
and adjusting the trim until the output code flickers between
0000 0000 0000 and 0000 0000 0001.

+

VIN1

VIN2

AGND

+

5REF

SUM

V

REF

5V

V

DD

AIN

±

+V

+V

IN

V

OUT

AD586

GND

5V

R3

5k

5V+

R1
82k

+
–

AD845

A1

AD707

–

+

3.5V–

AD7886*

R2

56k

*ADDITIONAL PINS OMITTED FOR CLARITY

C1

10µF

C2

0.1µF

V

SS

5V–

Figure 9. Bipolar Operation with Gain Error Adjust

TIMING AND CONTROL

Conversion start is controlled by the CONVST input (see Fig­ures 10 and 11). A high to low going edge on the

CONVST in­put puts the track/hold amplifier into the hold mode. The ADC
conversion procedure does not begin until a rising
pulse edge occurs. The width of the

CONVST pulse low time

determines the track-to-hold settling time. The

CONVST

BUSY output,

which indicates the status of the ADC, goes low while conver­sion is in progress. At the end of conversion

BUSY returns high,
indicating that new data is available on the AD7886’s output
latches. The track/hold amplifier returns to the track mode at
the end of conversion and remains there until the next
CONVST pulse. Conversion starts must not be attempted while
conversion is in progress as this will cause erroneous results.

Data read operations are controlled by the

CS and RD inputs.
These digital inputs, when low, enable the AD7886’s three­state output latches. Note, these latches cannot be enabled dur­ing conversion. In applications where

CS and RD are tied per­manently low, as in Figure 11, the data bus will go into the
three-state condition at the start of conversion and return to its
active state when conversion is complete. Tying

CS and RD
permanently low is useful when external latches are used to
store the conversion results. The data bus becomes active before
BUSY returns high at the end of conversion, so that BUSY can
be used as a clocking signal for the external latches.

A typical DSP application would have a timer connected to the
CONVST input for precise sampling intervals. BUSY would be
connected to the interrupt of a microprocessor that would be
asserted at the end of every conversion. The microprocessor
would then assert the

CS and RD inputs and read the data from
the ADC. For applications where both data reading and conver­sion control need to be managed by a microprocessor, a

CONVST

pulse can be decoded from the address bus. One decoding pos­sibility is that a write instruction to the ADC address starts a
conversion, and a read instruction reads the conversion result.

TRACK-TO-HOLD
TRANSITION

t

13

t

CONVST

CS

RD

BUSY

DATA

1

t

5

HIGH IMPEDANCE

CONVERSION
START

HOLD TO

TRACK

TRANSITION

t

CONV

t

11

t

t

12

t

10

t

2

t

4

6

DATA

VALID

t

3

t

7

Figure 10. Conversion Start and Data Read Timing

Diagram

TRACK-TO-HOLD
TRANSITION

t

13

t

1

CONVST

t

BUSY

DATA

CONVERSION
START

5

t

9

HIGH IMPEDANCE

t

CONV

t

12

HOLD TO TRACK

t

8

TRANSITION

DATA

VALID

Figure 11. Conversion Start and Data Read
Timing Diagram, (

CS

= RD = 0 V)

–8–

REV. B

AD7886

AD7886 DYNAMIC SPECIFICATIONS

The AD7886 is specified for dynamic performance specifica­tions as well as traditional dc specifications such as integral and
differential nonlinearity. These ac specifications are required for
signal processing applications such as speech recognition, spec­trum analysis and high speed modems. These applications require
information on the ADC’s effect on the spectral content of the
input signal. Hence, the parameters for which the AD7886 is
specified include SNR, harmonic distortion, intermodulation
distortion and peak harmonics. These terms are discussed in
more detail in the following sections.

Signal-to-Noise Ratio (SNR)

SNR is the measured signal-to-noise ratio at the output of the
ADC. The signal is the rms magnitude of the fundamental.
Noise is the rms sum of all the nonfundamental signals up to
half the sampling frequency (FS/2), excluding dc. SNR is de­pendent upon the number of quantization levels used in the
digitization process; the more levels, the smaller the quantiza­tion noise. The theoretical signal to noise ratio for a sine wave
input is given by

SNR = (6.02N + 1.76) dB (1)

where N is the number of bits. Thus, for an ideal 12-bit con­verter, SNR = 74 dB.

The output spectrum from the ADC is evaluated by applying a
sine wave signal of very low distortion to the VIN input, which
is sampled at a 750 kHz sampling rate. A Fast Fourier Trans­form (FFT) plot is generated from which the SNR data can be
obtained. Figure 12 shows a typical 2048 point FFT plot with
an input signal of 100 kHz and a sampling frequency of 750 kHz.

Figure 12. AD7886 FFT Plot

The SNR obtained from this graph is 68 dB. It should be noted
that the harmonics are taken into account when calculating the
SNR.

Effective Number of Bits

The formula given in Equation 1 relates the SNR to the number
of bits. Rewriting the formula, as in Equation 2, it is possible to
obtain a measure of performance expressed in effective num­ber of bits (N).

SNR –1.76

N =

6.02

(2)

The effective number of bits for a device can be calculated di­rectly from its measured SNR.

Figure 13 shows a typical plot of effective number of bits versus
frequency for a sampling frequency of 750 kHz. Input frequency
range for this particular graph was limited by the test equipment
to FS/4. The effective number of bits typically falls between

10.9 and 11.2, corresponding to SNR figures of 67.38 dB and

69.18 dB.

12

11.5

11

10.5

EFFECTIVE NUMBER OF BITS

10

0

SAMPLING FREQUENCY = 750kHz
T = 25 C

A

INPUT FREQUENCY

FS/4

Figure 13. Effective Number of Bits vs. Frequency

Total Harmonic Distortion (THD)

THD is the ratio of the rms sum of harmonics to the fundamen­tal. For the AD7886, THD is defined as

2

2

2

2

+V

+V

V

2

where V
V

, V5 and V6 are the rms amplitudes of the second through the

4

THD =20 log

is the rms amplitude of the fundamental and V2, V3,

1

3

+V

4

V

1

+V

5

2

6

(3)

sixth harmonic. The THD is also derived from the FFT plot of
the ADC output spectrum.

Intermodulation Distortion (IMD)

With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities will create distortion
products at sum and difference frequencies of mfa ± nfb where
m, n = 0, 1, 2, 3, etc. Intermodulation terms are those for which
neither m nor n are equal to zero. For example, the second or­der terms include (fa + fb) and (fa – fb) while the third order
terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa – 2fb).

Using the CCIF standard, where two input frequencies near the
top end of the input bandwidth are used, the second and third
order terms are of different significance. The second order terms
are usually distanced in frequency from the original sine waves,
while the third order terms are usually at a frequency close to
the input frequencies. As a result, the second and third order
terms are specified separately. The calculation of the intermodu­lation distortion is per the THD specification where it is the
ratio of the rms sum of the individual distortion products to the
rms amplitude of the fundamental, expressed in dBs. In this
case, the input consists of two, equal amplitude, low distortion
sine waves. Figure 14 shows a typical IMD plot for the AD7886.

Peak Harmonic or Spurious Noise

Peak harmonic or spurious noise is defined as the ratio of the
rms value of the next largest component in the ADC output
spectrum (up to FS/2 and excluding dc) to the rms value of the
fundamental. Normally, the value of this specification will be

REV. B

–9–

AD7886

determined by the largest harmonic in the spectrum, but for
parts where the harmonics are buried in the noise floor, the peak
will be a noise peak.

Figure 14. AD7886 IMD Plot

MICROPROCESSOR INTERFACING

The AD7886 is designed to interface to microprocessors as a
memory mapped device. Its

CS and RD control inputs are com­mon to all memory peripheral interfacing. Figures 15 to 21
demonstrate typical interfaces for the AD7886.

AD7886–TMS320C10/TMS32020

Figures 15 and 16 show typical interfaces for the TMS320C10
and the TMS32020 DSP processors. An external timer controls
conversion start to the processor. At the end of each conversion,
the ADC’s

BUSY output interrupts the microprocessor. The
conversion result can then be read from the ADC with the fol­lowing instruction:

IN D,ADC (ADC = ADC address)

AD788S ADSP-2100/TMS320C25/DSP56000

Some of the faster DSP processors have data access times out­side the capabilities of the AD7886. Interfacing to such proces­sors requires the use of either a single WAIT state or external
latches. Examples are shown in Figures 17, 18 and 19.

The use of a single WAIT state for the TMS320C25 and the
ADSP-2100 interfaces extends the read instruction to the ADC
by one processor CLK OUT cycle. In the DSP56000 example,
the ADC’s data is first clocked into 74HC374 latches before be­ing read by the processor. The AD7886’s
tied permanently low, and the rising edge of

CS and RD inputs are

BUSY updates the

latches at the end of conversion. Both methods of overcoming
the very fast data access time required by these processors are
interchangeable, i.e., a WAIT state can be used for the DSP56000,
eliminating the need for latches or vice or versa, for the other
two interfaces.

For all three interfaces, an external timer controls conversion
start; the processor is interrupted at the end of each conversion
by the ADC’s

BUSY output. The following instruction then

reads data from the ADC:

TIMER

PA2
PA0

MEN

ADDRESS BUS

ADDR

ENCODE

EN

TMS320C10

INT

DEN

D15

D0

*ADDITIONAL PINS OMITTED FOR CLARITY

DATA BUS

Figure 15. AD7886-TMS320C10 Interface

TIMER

A15

A0

IS

ADDRESS BUS

ADDR

ENCODE

EN

TMS32020

INTn

STRB

R/W

D15

D0

*ADDITIONAL PINS OMITTED FOR CLARITY

DATA BUS

Figure 16. AD7886-TMS32020 Interface

CONVST
CS

AD7886*

BUSY
RD

DB11
DB0

CONVST

CS

AD7886*

BUSY
RD

DB11
DB0

ADSP-2100 – MR = DM(ADC)
TMS320C25 – IN D,ADC
DSP56000 – MOVEP Y:ADC,XO
Assuming the ADC is memory mapped into the top
64 locations in Y memory space. (ADC = ADC address)

–10–

REV. B

AD7886

A0

A15

D11

D0

ADDR

ENCODE

ADDRESS BUS

DATA BUS

CONVST

CS

DB11

DB0

RD
BUSY

AD7886*

MC68000

*ADDITIONAL PINS OMITTED FOR CLARITY

R/W

EN

DTACK

AS

CLK

DMA13

OUT

DMA0

DMACK

ADSP-2100

DMRD

DMD15

DMD0

ADDRESS BUS

ADDR

ENCODE

DMS

IRQn

EN

Q

74HC74

DATA BUS

*ADDITIONAL PINS OMITTED FOR CLARITY

CLR

CLK

Figure 17. AD7886–ADSP-2100 Interface

A15

ADDRESS BUS

A0

TMS320C25

IS

ADDR

ENCODE

EN

TIMER

AD7886–MC68000

Applications requiring conversions to be initiated by the micro­processor rather than an external timer may decode a

CONVST

signal from the address bus. An example is given in Figure 20

CONVST

CS

AD7886*

+

5V

D

with the MC68000 processor. A write instruction starts conver­sion while a read instruction reads the data when conversion is
complete. A delay at least as long as the ADC conversion time
must be allowed between initiating a conversion and reading the
ADC data into the processor. In Figure 20,

BUSY is used to
drive the processor into a WAIT state if the processor attempts
to read data before conversion is complete.

BUSY
RD

DB11
DB0

Conversion is initiated with a write instruction to the ADC:
Move.W D0,ADC (ADC = ADC address)
Data is transferred to the processor with a read instruction;

BUSY will force the processor to WAIT for the end of conver­sion if a conversion is in progress.

Move.W ADC,DO (ADC = ADC address)

TIMER

CONVST

CS

READY

MSC

STRB

R/W

INT

D15

D0

G2

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 18. AD7886–TMS320C25 Interface

A15

A0

X/Y

DSP56000

REV. B

DS

IRQ

RD

D23

D0

Figure 19. AD7886–DSP56000 Interface

ADDRESS BUS

ADDR

EN1

ENCODE

EN2

DATA BUS

*ADDITIONAL PINS OMITTED FOR CLARITY

DATA BUS

CLKOE

Q11

D11

D0

Q0

2X

74HC374

AD7886*

RD

BUSY
DB11

DB0

TIMER

CONVST

CS
RD

BUSY

AD7886*

DB11
DB0

Figure 20. AD7886–MC68000 Interface

AD7886–Z-80/8085A

For 8-bit processors, an external latch is required to store four
bits of the conversion result (4 LSBs in Figure 21). The data is
then read in two bytes: one read from the ADC and a second
from the latch.

Figure 21 shows a typical interface suitable for the Z-80 or the
8085A. Not shown in the Figure is the 8-bit latch needed to
demultiplex the 8085A common address/data bus. The follow­ing LOAD instruction reads the conversion result into the HL
register pair:

For the 8085A–LHLD (ADC) (ADC = ADC address)
For the Z-80–LDHL (ADC) (ADC = ADC address)

This is a two byte read instruction. The first byte to be read has
to be the high byte (DB11 to DB4). At the end of the first read
operation, the rising edge of

CS and RD clocks the 4 LSBs into
74HC374 latches. The second byte (4 LSBs) is then read from
these latches.

–11–

AD7886

MREQ

Z-80

8085A

A15

A0

RD

INT

D7
D0

ADDRESS BUS

ADDR

ENCODE

EN

CLK

OE
Q3

D3

Q0

D0

74HC374

DATA BUS

*ADDITIONAL PINS OMITTED FOR CLARITY

TIMER

CONVST

CS

RD

BUSY

AD7886*

DB3
DB0
DB11
DB4

Figure 21. AD7886–Z-80/8085A Interface

APPLICATION HINTS

Good printed circuit (PC) board layout is as important as the
circuit design itself in achieving high speed A/D performance.
The AD7886’s comparators are required to make bit decisions
on an LSB size of 1.22 mV. To achieve this, the designer has to
be conscious of noise in both the ADC itself and in the preced­ing analog circuitry. Switching mode power supplies are not rec­ommended as the switching spikes will feed through to the
comparator, causing noisy code transitions. Other causes of con­cern are ground loops and digital feedthrough from micropro­cessors. These are factors that influence any ADC, and a proper
PC board layout that minimizes these effects is essential for best
performance.

LAYOUT HINTS

Ensure that the layout for the printed circuit board has the digi­tal and analog signal lines separated as much as possible. Take
care not to run any digital track alongside an analog signal track.
Guard (screen) the analog input with AGND.

Establish a single point analog ground (star ground) separate
from the logic system ground at the AD7886 AGND or as close
as possible to the AD7886. Connect all other grounds and the
AD7886 DGND to this single analog ground point. Do not
connect any other digital grounds to this analog ground point.

Because low impedance analog and digital power supply com­mon returns are essential to low noise operation of the ADC,
make the foil width for these tracks as wide as possible. The use
of ground planes minimizes impedance paths and also guards
the analog circuitry from digital noise. The circuit layout of Fig­ures 25 and 26 have both analog and digital ground planes that are
kept separated and only joined together at the AD7886 AGND.

NOISE

Keep the input signal leads to VIN and signal return leads from
AGND as short as possible to minimize input noise coupling. In
applications where this is not possible, use a shielded cable be­tween the source and the ADC. Reduce the ground circuit im­pedance as much as possible since any potential difference in
grounds between the signal source and the ADC appears as an
error voltage in series with the input signal.

–12–

DATA ACQUISITION BOARD

Figure 23 shows a typical data acquisition circuit designed for a
microprocessor environment. The corresponding PC board lay­out and silkscreen are shown in Figures 24 to 26.

The analog input to the AD7886 is buffered with an AD845 op
amp. A component grid is provided near the analog input on the
PC board that may be used for an antialiasing filter or any other
conditioning circuitry. To facilitate this option, a link (labeled
LK4) is required on the analog input.

An AD586 voltage reference and an AD707 op amp provide the
appropriate reference biasing required by the AD7886. The
ADC’s data outputs are buffered with 74HC374 latches. These
provide data bus isolation and improve data access time. Data
access time is reduced to under 30 ns, allowing interfacing to
virtually any microprocessor, including the high speed DSP pro­cessors. Data format can be either a complete parallel load for
16-bit processors or a two-byte load for 8-bit processors.

INTERFACE CONNECTIONS

There are two connectors labeled SKT3 and SKT4. SKT3 is a
96-contact (3-row) connector, which is directly compatible with
the ADSP-2100 evaluation board prototype expansion connec­tor. The expansion connector on the ADSP-2100 board has
eight decoded chip enable outputs labeled

ECE1 to ECE8.

ECE6 is used to select the AD7886 data acquisition board. To

avoid selecting on-board RAM sockets at the same time, LK6
on the ADSP-2100 board must be removed. In addition, the
ADSP-2100 expansion connector has four interrupts labeled

EIRQ0 to EIRQ3. The AD7886’s BUSY output connects to
EIRQ0. SKT3 pinout is shown in Figure 23.

Data format to the ADSP-2100 connector is left justified, i.e.,
DB11 of the conversion result is connected to DMD15 of the
connector. DMD3 to DMD0 are always zero.

SKT4 is a 22-way (2 row) pin-header connector. This connec­tor contains all the signal contacts as SKT3 with the exception
of EDMACK and the 4 trailing zeros of the 16-bit data word.
Only the 12-bit conversion results go to SKT4. The pinout is
shown in Figure 22.

DB0
DB2
DB4
DB6

DB8

DB10

BUSY

CS
NC

V

CC

DGND

NC = NO CONNECT

2122

DB1

1920

DB3

1718

DB5

1516

DB7

1314

DB9

1112

DB11

910

OUT1
8
6
4

7

OUT2

5

RD

V

3

CC

12

DGND

Figure 22. SKT4 Pinout

REV. B

AD7886

POWER SUPPLY CONNECTIONS

The PC board requires two analog power supplies and one 5 V
digital supply. Connections to the analog supply are made di­rectly to the PC board as shown on the silkscreen in Figure 24.
The connections are labeled V+ and V–, and the range for both
of these supplies is 12 V to 15 V. Connection to the 5 V digital
supply is made through either of the two connectors (SKT3 or
SKT4). The +5 V analog supplies required by the AD7886 are
generated from voltage regulators on the V– and V+ power
supplies.

LINK OPTIONS

There are five link options, labeled LK1 to LK5, which must be
set before using the board.

LK1 Input Range Select

The AD7886 can accommodate three possible analog input
ranges: 0 V to 5 V, 0 to 10 V and +5 V. The link options are as
follows:

0 V to 5 V Use Link C
0 V to 10 V Use Link B
±5 V Use Link A

LK2 and LK3 Control Input Options

The evaluation board includes two latches to increase the data
access time when interfacing to the faster DSP machines. If

V

DD

DB11

DB4

AD7886

DB3
DB0

BUSY

CS

RD
CONVST

OUT

+

5V

C8

0.1µF

V

+

IC1

DGND

AGND

AGND

V

SS

C10/C18

DD

5REF

SUM

V

REF

VIN1

VIN2

V

0.1µF

SS

C7
10µF

0.1µF

–

SKT3

96-WAY

CONNECTOR

A31

B11

B18

C22

B6

C11
B20
B27

A9

C14
C13
C12

A32/B32/

C32

C20

0.1µF

+

5V

DMD15

DMD8

ECE6 (OUT1)

EDMACK

LK5

OUT2
DMD7
DMD0

EIRQ0

CS
RD
CONVST

DIGITAL

GND

CONVST

+

5V

+

5V

Q7

Q0

O/P

74HC374

IC9

O/P
Q7
Q0

GND

LK2 LK3

SKT1

C19
10µF

V

CC

74HC374

IC8

GND

0.1µF

V

CC

CLK

+V

C23

D7
D4
D3
D2
D1
D0

D7

D0

CLK

IN

+

–V

OUT

78L05

IC5
GND

5V

IN

79L05

IC6

GND

these latches are not required, they may be removed and the
data digital paths shorted out, i.e., latch inputs Dx shorted to
outputs Qx using wire links in the latch sockets. When using the
latches, the AD7886 control inputs,

CS and RD, must be tied
low via links 2 and 3. The latches are updated by the rising edge
of the

BUSY signal at the end of every conversion. Data is then
read by asserting the latch output enable signals. The alternative
is to remove the latches and assert the ADC’s control inputs
from either of the connectors, SKT3 or SKT4, as outlined in
the data sheet.

Latches Included Latches Removed
Insert Link 2 Remove Link 2
Insert Link 3 Remove Link 3

LK4 Analog Input Option

LK4 connects the analog input to a component grid or to a
buffer amplifier that drives the ADC input.

LK5

Data format can be 16-bits parallel or two bytes for 8-bit pro­cessors. There are two data enable controls for the 74HC374
latches, labeled
(IC8), and

OUT1 and OUT2. OUT1 enables the 8 MSBs

OUT2 enables the 4 LSBs (IC9). Link options are:

for 16-bit format, include LK5, for a two byte read format,
remove LK5.

+V

C10

5V

C14

0.1µF

10µF

C9/C17
10µF

C11

A

C

B

C13
10µF

IC4

AD707

C16

0.1µF

LK1

–
+

C4

0.1µF

–V

C15
10µF

+V

C3
10µF

IC2

AD845

C2

0.1µF

V

OUT

AD586

IC3

GND

–
+

–V

+V

IN

0.1µF

LK4

C1
10µF

C6

SKT2

ANALOG

+V

INPUT

C5
10µF

REV. B

Figure 23. Data Acquisition Circuit Using the AD7886

–13–

AD7886

COMPONENT LIST

IC1 AD7886, 12-Bit Sampling ADC
IC2 AD845, Op Amp
IC3 AD586, Precision Voltage Reference
IC4 AD707, Op Amp
IC5 MC78L05, + 5 V Regulator
IC6 MC79L05, –5 V Regulator
IC7 74HC04, Hex Inverter
IC8, IC9 74HC374, Octal Latches with Three-State

Outputs

C1, C3, C5, C7,
C9, C11, C13, C15 10 µF Capacitors
C17, C19, C21
C2, C4, C6, C8,
C10, C12, C14,
C16, C18, C20, 0.1 µF Capacitors
C22, C23
SKT1, SKT2 BNC Sockets
SKT3 96-Contact (3 Row) Eurocard Connector
SKT4 22-Way (2 Row) Pin Header and Socket

Figure 24. PC Board Silkscreen for Figure 23

–14–

REV. B

AD7886

Figure 25. PC Board Component Side Layout for Figure 23

REV. B

Figure 26. PC Board Solder Side Layout for Figure 23

–15–

AD7886

0.048 (1.21)

0.042 (1.07)

0.020

(0.50)

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

28-Pin Ceramic DIP (D-28)

28-Pin PLCC (P-28A)

0.180 (4.57)

0.050
(1.27)
BSC

0.165 (4.19)

0.110 (2.79)

0.085 (2.16)

0.048 (1.21)

0.042 (1.07)

4

5

11

12

0.456 (11.58)

R

0.450 (11.43)

0.495 (12.57)

0.485 (12.32)

PIN 1

IDENTIFIER

TOP VIEW

(PINS DOWN)

0.056 (1.42)

0.042 (1.07)

26

25

19

18

SQ

SQ

0.025 (0.63)

0.015 (0.38)

0.021 (0.53)

0.013 (0.33)

0.032 (0.81)

0.026 (0.66)

0.040 (1.01)

0.025 (0.64)

C1485b–10–4/91

0.430 (10.92)

0.390 (9.91)

–16–

PRINTED IN U.S.A.

REV. B