Datasheet AD7899 Datasheet (Analog Devices)

5 V Single Supply

a

FEATURES
Fast (2.2 ␮s) 14-Bit ADC
400 kSPS Throughput Rate

0.3 ␮s Track/Hold Acquisition Time
Single Supply Operation
Selection of Input Ranges: ⴞ10 V, ⴞ5 V and ⴞ2.5 V

0 V to 2.5 V and 0 V to 5 V

High-Speed Parallel Interface which Also Allows

Interfacing to 3 V Processors
Low Power, 80 mW Typ
Power-Saving Mode, 20 ␮W Typ
Overvoltage Protection on Analog Inputs
Power-Down Mode via STBY Pin

GENERAL DESCRIPTION

The AD7899 is a fast, low-power, 14-bit A/D converter that
operates from a single 5 V supply. The part contains a 2.2 µs
successive-approximation ADC, a track/hold amplifier, 2.5 V
reference, on-chip clock oscillator, signal conditioning circuitry,
and a high-speed parallel interface. The part accepts analog input
ranges of ±10 V, ± 5 V, ± 2.5 V, 0 V to 2.5 V, and 0 V to 5 V.
Overvoltage protection on the analog input for the part allows
the input voltage to be exceeded without damaging the parts.

Speed of conversion can be controlled either by an internally
trimmed clock oscillator or by an external clock.

A conversion start signal (CONVST) places the track/hold into
hold mode and initiates conversion. The BUSY/EOC signal
indicates the end of the conversion.

Data is read from the part via a 14-bit parallel data bus using the
standard CS and RD signals. Maximum throughput for the
AD7899 is 400 kSPS.

The AD7899 is available in a 28-lead SOIC and SSOP packages.

14-Bit 400 kSPS ADC

AD7899

FUNCTIONAL BLOCK DIAGRAM

V

REF

6k⍀

REFERENCE

+

–

14-BIT

ADC

CONVERSION

CONTROL

LOGIC

CONVST OPGNDGND

INT/EXT

CLOCK

SELECT

CLKIN

STBY

V

INA

V

INB

BUSY/EOC

AVDD

AD7899

TRACK/HOLD

SIGNAL

SCALING

PRODUCT HIGHLIGHTS

1. The AD7899 features a fast (2.2 µs) ADC allowing through­put rates of up to 400 kSPS.

2. The AD7899 operates from a single 5 V supply and con­sumes only 80 mW typ making it ideal for low power and
portable applications.

3. The part offers a high-speed parallel interface. The interface
can operate in 3 V and 5 V mode allowing for easy connec­tion to 3 V or 5 V microprocessors, microcontrollers, and
digital signal processors.

4. The part is offered in three versions with different analog
input ranges. The AD7899-1 offers the standard industrial
ranges of ±10 V and ± 5 V; the AD7899-2 offers a unipolar
range of 0 V to 2.5 or 0 V to 5 V, and the AD7899-3 has an
input range of ±2.5 V.

2.5V

V

DRIVE

OUTPUT

LATCH

CLOCK

RD

DB13

DB0

CS

INT

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 that
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] www.analog.com
Fax: [phone] © Analog Devices, Inc., 2001

AD7899–SPECIFICATIONS

(VDD = 5 V ⴞ 5%, AGND = DGND = 0 V, V
T

to T

MIN

and valid for V

MAX

= 3 V ⴞ 5% and 5 V ⴞ 5% unless otherwise noted.)

DRIVE

= Internal. Clock = Internal, all specifications

REF

ABS

Parameter Version

1

Version

1

Version

1

Unit Test Conditions/Comments

SAMPLE AND HOLD

–0.1 dB Full Power Bandwidth 500 500 500 kHz typ
–3 dB Full Power Bandwidth 4.5 4.5 4.5 MHz typ

Aperture Delay 20 20 20 ns max
Aperture Jitter 25 25 25 ps typ

DYNAMIC PERFORMANCE

2

fIN = 100 kHz, fS = 400 kSPS

AD7899-1

Signal to (Noise + Distortion)

3

@ 25C 78 78 78 dB min

Ratio

to T

T

MIN

Total Harmonic Distortion

MAX

3

Peak Harmonic or Spurious Noise

78 78 77 dB min
–84 –84 –82 dB max

3

–86 –86 –85 dB max

AD7899-2

Signal to (Noise + Distortion)

3

@ 25C 78 dB min

Ratio

to T

T

MIN

Total Harmonic Distortion

MAX

3

Peak Harmonic or Spurious Noise

77 dB min
–82 dB max

3

–82 dB max

AD7899-3

Signal to (Noise + Distortion)

3

@ 25C 78 78 dB min

Ratio

to T

T

MIN

Total Harmonic Distortion
Peak Harmonic or Spurious Noise

Intermodulation Distortion

MAX

3

3

77 77 dB min
–84 –84 dB max

3

–86 –86 dB max

fa = 49 kHz, fb = 50 kHz
2nd Order Terms –89 –89 –89 dB typ
3rd Order Terms –89 –89 –89 dB typ

DC ACCURACY

Resolution 14 14 14 Bits
Relative Accuracy (INL)
Differential Nonlinearity (DNL)

3

± 2 ± 1.5 ±2 LSB max

3

± 1 ± 1 ± 1 LSB max No Missing Codes Guaranteed

AD7899-1

Input Voltage Range ± 5, ± 10 ± 5, ± 10 Volts
Input Current 0.8, 0.8 0.8, 0.8 mA max V
Positive Gain Error
Negative Gain Error

3

3

± 10 ± 8 ± 12 LSB max
± 10 ± 8 ± 12 LSB max

= –5 V and –10 V Respectively

IN

Bipolar Zero Error ± 12 ± 8 ± 12 LSB max

AD7899-2

Input Voltage Range 0 to 2.5 Volts

0 to 5
Input Current 0.4, 800 µA max V
Positive Gain Error
Offset Error

3

3

± 14 LSB max

± 10 LSB max

= 2.5 V, VIN = 5 V

IN

AD7899-3

Input Voltage Range ± 2.5 ± 2.5 Volts
Input Current 0.8 0.8 mA max V
Positive Gain Error
Negative Gain Error

3

3

± 14 ± 12 LSB max

± 14 ± 12 LSB max

= –2.5 V

IN

Bipolar Zero Error ± 14 ± 12 LSB max

REFERENCE INPUT/OUTPUT

V

IN Input Voltage Range 2.375/2.625 2.375/2.625 2.375/2.625 V

REF

IN Input Capacitance

V

REF

V

OUT Output Voltage 2.5 2.5 2.5 V nom

REF

OUT Error @ 25C ± 10 ± 10 ± 10 mV max

V

REF

OUT Error T

V

REF

V

OUT Temperature Coefficient 25 25 25 ppm/C typ

REF

V

OUT Output Impedance 6 6 6 kΩ typ See Reference Section

REF

MIN

to T

4

MAX

10 10 10 pF max

± 20 ± 20 ± 25 mV max

MIN/VMAX

2.5 V ± 5%

–2–

REV. A

AD7899

ABS

Parameter Version

L

OGIC INPUTS

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

IN

Input Capacitance, C

INH

INL

IN

4

V
V
± 10 ± 10 ± 10 µA max
10 10 10 pF max

DRIVE

DRIVE

1

/2 + 0.4 V
/2 – 0.4 V

Version

/2 + 0.4 V

DRIVE

/2 – 0.4 V

DRIVE

1

Version

1

/2 + 0.4 V min VDD = 5 V ± 5%

DRIVE

/2 – 0.4 V max VDD = 5 V ± 5%

DRIVE

Unit Test Conditions/Comments

LOGIC OUTPUTS

Output High Voltage, V
Output Low Voltage, V

OL

OH

– 0.4 V

DRIVE

0.4 0.4 0.4 V max I

DRIVE

– 0.4 V

– 0.4 V min I

DRIVE

SOURCE

= 1.6 mA

SINK

= 400 µA

V

DB13–DB0

High Impedance

Leakage Current ± 10 ± 10 ± 10 µA max
Capacitance

4

10 10 10 pF max

Output Coding

AD7899-1, AD7899-3 Two’s Complement
AD7899-2 Straight (Natural) Binary

CONVERSION RATE

Conversion Time 2.2 2.2 2.2 µs max
Track/Hold Acquisition Time

2, 3

0.3 0.3 0.3 µs max

Throughput Time 400 400 400 kSPS max

POWER REQUIREMENTS

V

DD

I

DD

5 5 5 V nom

Normal Mode 25 25 25 mA max Typically 16 mA
Standby Mode 20 20 20 µA max (5 µA typ) Logic Inputs = 0 V or

V

DD

Power Dissipation

Normal Mode 125 125 125 mW max Typically 80 mW, V

DD

Standby Mode 100 100 125 µW max

NOTES

1

Temperature Ranges are as follows : A, B Versions: –40C to +85C. S Version: –55°C to +125°C.

2

Performance measured through full channel (SHA and ADC).

3

See Terminology.

4

Sample tested @ 25°C to ensure compliance.

Specifications subject to change without notice.

= 5 V

REV. A

–3–

AD7899

1, 2

TIMING CHARACTERISTICS

to T

and valid for V

MAX

= 3 V ⴞ 5% and 5 V ⴞ 5% unless otherwise noted.)

DRIVE

(VDD = 5 V ⴞ 5%, AGND = DGND = 0 V, V

A, B and S

Parameter Versions Unit Test Conditions/Comments

t

CONV

2.2 µs max Conversion Time, Internal Clock

2.46 µs max CLKIN = 6.5 MHz

t

ACQ

t

EOC

t

WAKE-UP

– External V

REF

5

0.3 µs max Acquisition Time
120 ns min EOC Pulsewidth
180 ns max
2 µs max STBY Rising Edge to CONVST Rising Edge

(See Standby Mode Operation)

t

1

t

2

35 ns min CONVST Pulsewidth
70 ns min CONVST Rising Edge to BUSY Rising Edge

Read Operation

t

3

t

4

t

5

3

t

6

4

t

7

0 ns min CS to RD Setup Time
0 ns min CS to RD Hold Time
35 ns min Read Pulsewidth
35 ns max Data Access Time after Falling Edge of RD, V
40 ns max Data Access Time after Falling Edge of RD, V
5 ns min Bus Relinquish Time after Rising Edge of RD
30 ns max

t

8

0 ns min BUSY Falling Edge to RD Delay

External Clock

t

9

t

10

t

11

NOTES

1

Sample tested at 25°C to ensure compliance. All input signals are measured with tr = tf = 1 ns (10% to 90% of V

2

See Figures 5, 6, 7, and 8.

3

Measured with the load circuit of Figure 1 and defined as the time required for an output to cross 0.8 V or 2.0 V.

4

These times are derived from the measured time taken by the data outputs to change 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 50 pF capacitor. This means that the times quoted in the timing characteristics are the true bus
relinquish times of the part and as such are independent of external bus loading capacitances.

5

Refer to the Standby Mode Operation section.

Specifications subject to change without notice.

0 ns min CLKIN to CONVST Rising Edge Setup Time
20 ns min CLKIN to CONVST Rising Edge Hold Time
100 ns min CONVST Rising Edge to CLK Falling Edge

= Internal, Clock = Internal; All specifications T

REF

DRIVE

DRIVE

) and timed from a voltage level of V

DRIVE

= 5 V
= 3 V

/2.

DRIVE

MIN

1.6mA

OUTPUT

PIN

TO

50pF

400␮A

1.6V

Figure 1. Load Circuit for Access Time and Bus Relinquish Time

–4–

REV. A

AD7899

WARNING!

ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS*

(TA = 25°C unless otherwise noted)

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

V

to DGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V

DD

V

to DGND . . . . . . . . . . . . . . . . . . . . . . . . . V

DRIVE

+ 0.3 V

DD

Analog Input Voltage to AGND

AD7899-1 (±10 V Range) . . . . . . . . . . . . . . . . . . . . ± 18 V

AD7899-1 (±5 V Range) . . . . . . . . . . . . . . . –9 V to +18 V

AD7899-2 . . . . . . . . . . . . . . . . . . . . . . . . . . –1 V to +18 V

AD7899-3 . . . . . . . . . . . . . . . . . . . . . . . . . . –4 V to +18 V

Reference Input Voltage to AGND . . . –0.3 V to V

Digital Input Voltage to DGND . . . . . –0.3 V to V

Digital Output Voltage to DGND . . . . –0.3 V to V

+ 0.3 V

DD

+ 0.3 V

DD

+ 0.3 V

DD

Operating Temperature Range

Commercial (A, B Version) . . . . . . . . . . . –40°C to +85°C

SOIC Package, Power Dissipation . . . . . . . . . . . . . . . 450 mW

Thermal Impedance . . . . . . . . . . . . . . . . . . . . . . . 95°C/W

θ

JA

Lead Temperature, Soldering

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . 215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . 220°C

SSOP Package, Power Dissipation . . . . . . . . . . . . . . . 450 mW

Thermal Impedance . . . . . . . . . . . . . . . . . . . . . . . 95°C/W

θ

JA

Lead Temperature, Soldering

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . 215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . 220°C

*

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.

Military (S Version) . . . . . . . . . . . . . . . . . –55°C to +125°C

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

Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . 150°C

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 AD7899 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

Relative Temperature Package Package

Model Input Ranges Accuracy Range Description Option

±

AD7899AR-1
AD7899BR-1
AD7899SR-1

5V, ±10 V

±

5V, ±10 V

±

5V, ±10 V
AD7899AR-2 0 V to 5 V, 0 V to 2.5 V
AD7899AR-3
AD7899BR-3
AD7899ARS-1

±

2.5 V

±

2.5 V

±

5V, ±10 V
AD7899ARS-2 0 V to 5 V, 0 V to 2.5 V
AD7899ARS-3

±

2.5 V

±

2 LSB –40C to +85C Small Outline R-28

±

1.5 LSB –40C to +85C Small Outline R-28

±

2 LSB –55C to +125C Small Outline R-28

±

2 LSB –40C to +85C Small Outline R-28

±

2 LSB –40C to +85C Small Outline R-28

±

1.5 LSB –40C to +85C Small Outline R-28

±

2 LSB –40C to +85C Shrink Small Outline RS-28

±

2 LSB –40C to +85C Shrink Small Outline RS-28

±

2 LSB –40C to +85C Shrink Small Outline RS-28

REV. A

–5–

AD7899

PIN FUNCTION DESCRIPTIONS

Pin
No. Mnemonic Description

1V

REF

2, 6 GND Ground Pin. This pin should be connected to the system’s analog ground
3, 4 V
5V

INB

DD

, V

INA

7–13 DB13–DB7 Data Bit 13 is the MSB, followed by Data Bit 12 to Data Bit 7. Three-state outputs.
14 OPGND Output Driver Ground. This is the ground pin of the output drivers for D13 to D0 and BUSY/EOC. It should

15 V

DRIVE

16–22 DB6–DB0 Data Bit 6 to Data Bit 0. Three-state Outputs.
23 BUSY/EOC BUSY/EOC Output. Digital output pin used to signify that a conversion is in progress or that a conversion

24 RD Read Input. Active low logic input which is used in conjunction with CS low to enable the data outputs.
25 CS Chip Select Input. Active low logic input. The device is selected when this input is active.
26 CONVST Convert Start Input. Logic Input. A low to high transition on this input puts the track/hold into hold mode

27 CLKIN Conversion Clock Input. CLKIN is an externally applied clock which allows the user to control the

28 STBY Standby Mode Input. Logic input which is used to put the device into the power save or standby mode.

Reference Input/Output. This pin is provides access to the internal reference (2.5 V ± 20 mV) and
also allows the internal reference to be overdriven by an external reference source (2.5 V ± 5%).
A 0.1 µF decoupling capacitor should be connected between this pin and GND.

plane.
Analog Inputs. See Analog Input Section.
Positive Supply Voltage, 5.0 V ± 5%.

be connected to the system’s analog ground plane
This pin provides the positive supply voltage for the digital inputs and outputs. It is normally tied to V

.

DD

but may also be powered by a 3 V ± 10% supply which allows the inputs and outputs to be interfaced
to 3 V processors and DSPs. V

should be decoupled with a 0.1 µF capacitor to GND.

DRIVE

has finished. The function of the BUSY/EOC is determined by the state of CONVST at the end of con­version. See the Timing and Control Section.

and starts conversion.

conversion rate of the AD7899. If the CLKIN input is high on the rising edge of CONVST an externally
applied clock will be used as the conversion clock. If the CLKIN is low on the rising edge of CONVST
the internal laser-trimmed oscillator is used as the conversion clock. Each conversion needs sixteen clock
cycles in order for the conversion to be completed. The externally applied clock should have a duty cycle
no greater than 60/40. The CLKIN pin can be tied to GND if an external clock is not required.

The STBY input is high for normal operation and low for standby operation.

PIN CONFIGURATION

SOIC/SSOP

V

REF

GND

V

INB

V

INA

V

GND

DB13

DB12

DB11

DB10

DB9

DB8

DB7

OPGND

DD

10

11

12

13

14

1

2

3

4

5

6

AD7899

7

TOP VIEW

(Not to Scale)

8

9

28

STBY

27

CLKIN

26

CONVST

25

CS

24

RD

23

BUSY/EOC

22

DB0

DB1

21

DB2

20

DB3

19

DB4

18

DB5

17

DB6

16

V

15

DRIVE

–6–

REV. A

AD7899

TERMINOLOGY
Signal to (Noise + Distortion) Ratio

This is the measured ratio of signal to (noise + distortion) at the
output of the A/D converter. The signal is the rms amplitude of
the fundamental. Noise is the rms sum of all nonfundamental
signals up to half the sampling frequency (f

/2), excluding dc.

S

The ratio is dependent upon the number of quantization levels
in the digitization process; the more levels, the smaller the quan­tization noise. The theoretical signal to (noise + distortion) ratio
for an ideal N-bit converter with a sine wave input is given by:

Signal to (Noise + Distortion) = (6.02N + 1.76) dB

Thus for a 14-bit converter, this is 86.04 dB.

Total Harmonic Distortion

Total harmonic distortion (THD) is the ratio of the rms sum of
harmonics to the fundamental. For the AD7899 it is defined

2

THD dB

as:

( ) log=

20

VVVVV

++++

223242526

V

1

where V1 is the rms amplitude of the fundamental and V2, V3,

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

V

4

fifth harmonics.

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 f

/2 and excluding dc) to the rms value of the

S

fundamental. Normally, the value of this specification is deter­mined by the largest harmonic in the spectrum, but for parts
where the harmonics are buried in the noise floor, it will be a
noise peak.

Intermodulation Distortion

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).

The AD7899 is tested using two input frequencies. In this case, 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 as 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.

Differential Nonlinearity

This is the difference between the measured and the ideal
1 LSB change between any two adjacent codes in the ADC.

Positive Gain Error (AD7899-1, AD7899-3)

This is the deviation of the last code transition (01 . . . 110 to
01 . . . 111) from the ideal 4 × V
± 10 V), 2 × V

– 3/2 LSB (AD7899 at ± 5 V range) or V

REF

– 3/2 LSB (AD7899 at

REF

REF

– 3/2 LSB (AD7899 at ± 2.5 V range) after the Bipolar Offset
Error has been adjusted out.

Positive Gain Error (AD7899-2)

This is the deviation of the last code transition (11 . . . 110 to
11 . . . 111) from the ideal 2 × V
± 10 V), 2 × V

– 3/2 LSB (AD7899 at 0 V to 2.5 V range) after the Uni-

V

REF

– 3/2 LSB (AD7899 at 0 V to 5 V range) or

REF

– 3/2 LSB (AD7899 at

REF

polar Offset Error has been adjusted out.

Unipolar Offset Error (AD7899-2)

This is the deviation of the first code transition (00 . . . 00 to
00 . . . 01) from the ideal AGND +1/2 LSB

Bipolar Zero Error (AD7899-1, AD7899-2)

This is the deviation of the midscale transition (all 0s to all 1s)
from the ideal AGND – 1/2 LSB.

Negative Gain Error (AD7899-1, AD7899-3)

This is the deviation of the first code transition (10 . . . 000 to
10 . . . 001) from the ideal –4 × V
± 10 V), –2 × V

+ 1/2 LSB (AD7899 at ±5 V range) or –V

REF

+ 1/2 LSB (AD7899 at

REF

REF

+ 1/2 LSB (AD7899 at ±2.5 V range) after Bipolar Zero Error
has been adjusted out.

Track/Hold Acquisition Time

Track/Hold acquisition time is the time required for the output
of the track/hold amplifier to reach its final value, within ±1/2 LSB,
after the end of conversion (the point at which the track/hold
returns to track mode). It also applies to situations where there
is a step input change on the input voltage applied to the selected
V

input of the AD7899. It means that the user must wait

INA/VINB

for the duration of the track/hold acquisition time after the end
of conversion or after a step input change to V

INA/VINB

before
starting another conversion, to ensure that the part operates to
specification.

REV. A

–7–

AD7899

CONVERTER DETAILS

The AD7899 is a high-speed, low-power, 14-bit A/D converter
that operates from a single 5 V supply. The part contains a

2.2 µs successive-approximation ADC, track/hold amplifier, an
internal 2.5 V reference and a high-speed parallel interface. The
part accepts an analog input range of ±10 V or ±5 V (AD7899-1),
0 V to 2.5 V or 0 V to 5 V (AD7899-2) and ±2.5 V (AD7899-3).
Overvoltage protection on the analog inputs for the part allows
the input voltage to go to ±18 V (AD7899-1 with ±10 V input
range), –9 V to +18 V (AD7899-1 with ± 5 V input range), –1 V
to +18 V (AD7899-2) and –4 V to +18 V (AD7899-3) without
causing damage.

A conversion is initiated on the AD7899 by pulsing the CONVST
input. On the rising edge of CONVST, the on-chip track/hold is
placed into hold and the conversion is started. The BUSY/EOC
output signal is triggered high on the rising edge of CONVST
and will remain high for the duration of the conversion sequence.
The conversion clock for the part is generated internally using a
laser-trimmed clock oscillator circuit. There is also the option of
using an external clock. An external noncontinuous clock is applied
to the CLKIN pin. If, on the rising edge of CONVST, this input
is high, the external clock will be used. The external clock should
not start until 100 ns after the rising edge of CONVST. The
optimum throughput is obtained by using the internally gener­ated clock—see Using an External Clock. The BUSY/EOC signal
indicates the end of the conversion, and at this time the Track and
Hold returns to tracking mode. The conversion results can be
read at the end of the conversion (indicated by BUSY/EOC
going low) via a 14-bit parallel data bus with standard CS and RD
signals—see Timing and Control.

Conversion time for the AD7899 is 2.2 µs and the track/hold
acquisition time is 0.3 µs. To obtain optimum performance from
the part, the read operation should not occur during a conversion
or during the 150 ns prior to the next CONVST rising edge.
This allows the part to operate at throughput rates up to 400 kHz
and achieve data sheet specifications.

CIRCUIT DESCRIPTION
Track/Hold Section

The track/hold amplifier on the AD7899 allows the ADCs to
accurately convert an input sine wave of full-scale amplitude to
14-bit accuracy. The input bandwidth of the track/hold is greater
than the Nyquist rate of the ADC even when the ADC is oper­ated at its maximum throughput rate of 400 kSPS (i.e., the
track/hold can handle input frequencies in excess of 200 kHz).

The track/hold amplifier’s acquire input signals to 14-bit
accuracy in less than 300 ns The operation of the track/hold is
essentially transparent to the user. The track/hold amplifier
samples the input channel on the rising edge of CONVST. The
aperture time for the track/hold (i.e., the delay time between the

external CONVST signal and the track/hold actually going into
hold) is typically 15 ns and, more importantly, is well matched
from device to device. It allows multiple AD7899s to sample
more than one channel simultaneously. At the end of a conversion,
the part returns to its tracking mode. The acquisition time of
the track/hold amplifier begins at this point.

Reference Section

The AD7899 contains a single reference pin, labelled

V

,

REF

which either provides access to the part’s own 2.5 V reference or
allows an external 2.5 V reference to be connected to provide
the reference source for the part. The part is specified with a

2.5 V reference voltage.

To use the internal reference as the reference source for the
AD7899, simply connect a 0.1 µF capacitor from the

V

pin

REF

to AGND. The voltage that appears at this pin is internally
buffered before being applied to the ADC. If this reference is
required for use external to the AD7899, it should be buffered,
as the part has a FET switch in series with the reference output
resulting in a source impedance for this output of 6 kΩ nominal.
The tolerance on the internal reference is ±10 mV at 25°C with
a typical temperature coefficient of 25 ppm/°C and a maximum
error over temperature of ±20 mV.

If the application requires a reference with a tighter tolerance or
the AD7899 needs to be used with a system reference, the user
has the option of connecting an external reference to this

V

REF

pin. The external reference will effectively overdrive the internal
reference and thus provide the reference source for the ADC.
The reference input is buffered before being applied to the ADC
with the maximum input current of ±100 µA. Suitable reference
sources for the AD7899 include the AD680, AD780, REF192,
and REF43 precision 2.5 V references.

Analog Input Section

The AD7899 is offered as three part types, the AD7899-1 where
the input can be configured for ±10 V or a ± 5 V input voltage
range, the AD7899-2 where the input can be configured for 0 V
to 5 V or a 0 V to 2.5 V input voltage range and the AD7899-3
which handles input voltage range ±2.5 V. The amount of current
flowing into the analog input will depend on the analog input
range and the analog input voltage. The maximum current flows
when negative full-scale is applied.

AD7899-1

Figure 2 shows the analog input section of the AD7899-1. The
input can be configured for ±5 V or ±10 V operation on the
AD7899-1. For ±5 V operation, the V

INA

and V

inputs are

INB

tied together and the input voltage is applied to both. For ±10 V
operation, the V
is applied to the V

input is tied to AGND and the input voltage

INB

input. The V

INA

INA

and V

inputs are sym-

INB

metrical and fully interchangeable.

–8–

REV. A

AD7899

AD7899-2

V

INA

TRACK/HOLD

TO ADC
REFERENCE
CIRCUITRY

TO INTERNAL
COMPARATOR

R1

6k⍀

2.5V

REFERENCE

R2

V

INB

V

REF

AD7899-1

2.5V

REFERENCE

6k⍀

TO ADC

GND

REFERENCE
CIRCUITRY

TRACK/HOLD

TO INTERNAL
COMPARATOR

V

REF

V

INA

V

INB

R2

R3

R1

R4

Figure 2. AD7899-1 Analog Input Structure

For the AD7899-1, R1 = 4 kΩ, R2 = 16 kΩ, R3 = 16 kΩ and
R4 = 8 kΩ. The resistor input stage is followed by the high
input impedance stage of the track/hold amplifier.

The designed code transitions take place midway between suc­cessive integer LSB values (i.e., 1/2 LSB, 3/2 LSBs, 5/2 LSBs
etc.) LSB size is given by the formula, 1 LSB = FSR/16384. For
the ± 5 V range, 1 LSB = 10 V/16384 = 610.4 µV. For the ± 10 V
range, 1 LSB = 20 V/16384 = 1.22 mV. Output coding is
two’s complement binary with 1 LSB = FSR/16384. The ideal
input/output transfer function for the AD7899-1 is shown in
Table I.

AD7899-2

Figure 3 shows the analog input section of the AD7899-2. Each
input can be configured for 0 V to 5 V operation or 0 V to 2.5 V
operation. For 0 V to 5 V operation, the V
GND and the input voltage is applied to the V
0 V to 2.5 V operation, the V

INA

and V

INB

and the input voltage is applied to both. The V

input is tied to

INB

input. For

INA

inputs are tied together

and V

INA

INB

inputs are symmetrical and fully interchangeable.

For the AD7899-2, R1 = 4 kΩ and R2 = 4 kΩ. Once again, the
designed code transitions occur on successive integer LSB values.
Output coding is straight (natural) binary with 1 LSB = FSR/
16384 = 2.5 V/16384 = 0.153 mV, and 5 V/16384 = 0.305 mV,
for the 0 to 2.5 V and the 0 to 5 V options respectively. Table
II shows the ideal input and output transfer function for the
AD7899-2.

Table I. Ideal Input/Output Code Table for the AD7899-1

Analog Input

1

+FSR/2 – 3/2 LSB

2

Digital Output
Code Transition

011 . . . 110 to 011 . . . 111
+FSR/2 – 5/2 LSB 011 . . . 101 to 011 . . . 110
+FSR/2 – 7/2 LSB 011 . . . 100 to 011 . . . 101

GND + 3/2 LSB 000 . . . 001 to 000 . . . 010
GND + 1/2 LSB 000 . . . 000 to 000 . . . 001
GND – 1/2 LSB 111 . . . 111 to 000 . . . 000
GND – 3/2 LSB 111 . . . 110 to 111 . . . 111

–FSR/2 + 5/2 LSB 100 . . . 010 to 100 . . . 011
–FSR/2 + 3/2 LSB 100 . . . 001 to 100 . . . 010
–FSR/2 + 1/2 LSB 100 . . . 000 to 100 . . . 001

NOTES

1

FSR is full-scale range and is 20 V for the ±10 V range and 10 V for the ±5 V
range, with V

2

1 LSB = FSR/16384 = 1.22 mV (± 10 V – AD7899-1) and 610.4 µV (±5 V –
AD7899-1) with V

= 2.5 V.

REF

= 2.5 V.

REF

Analog Input

+FSR – 3/2 LSB
+FSR – 5/2 LSB 111 . . . 101 to 111 . . . 110
+FSR – 7/2 LSB 111 . . . 100 to 111 . . . 101

GND + 5/2 LSB 000 . . . 010 to 000 . . . 011
GND + 3/2 LSB 000 . . . 001 to 000 . . . 010
GND + 1/2 LSB 000 . . . 000 to 000 . . . 001

NOTES

1

FSR is Full-Scale Range and is 0 to 2.5 V and 0 to 5 V for AD7899-2 with V
= 2.5 V.

2

1 LSB = FSR/16384 and is 0.153 mV (0 to 2.5 V) and 0.305 mV (0 to 5 V) for
AD7899-2 with V

Figure 3. AD7899-2 Analog Input Structure

Table II. Ideal Input/Output Code Table for the AD7899-2

1

REF

2

= 2.5 V.

Digital Output
Code Transition

111 . . . 110 to 111 . . . 111

REF

REV. A

–9–

AD7899

AD7899-3

Figure 4 shows the analog input section of the AD7899-3. The
analog input range is ±2.5 V on the V

input. The V

INA

INB

input
can be left unconnected but if it is connected to a potential then
that potential must be GND.

AD7899-3

2.5V

REFERENCE

6k⍀

TO ADC

V

REF

V

INA

V

INB

R2

R1

REFERENCE
CIRCUITRY

TRACK/HOLD

TO INTERNAL
COMPARATOR

Figure 4. AD7899-3 Analog Input Structure

For the AD7899-3, R1 = 4 kΩ and R2 = 4 kΩ. The resistor
input stage is followed by the high input impedance stage of the
track/hold amplifier.

The designed code transitions take place midway between suc­cessive integer LSB values (i.e., 1/2 LSB, 3/2 LSBs, 5/2 LSBs
etc.) LSB size is given by the formula, 1 LSB = FSR/16384.
Output coding is two’s complement binary with 1 LSB = FSR/
16384 = 5 V/16384 = 610.4 µV. The ideal input/output transfer
function for the AD7899-3 is shown in Table III.

Table III. Ideal Input/Output Code Table for the AD7899-3

Analog Input

l

+FSR/2 – 3/2 LSB

2

Digital Output
Code Transition

011 . . . 110 to 011 . . . 111
+FSR/2 – 5/2 LSB 011 . . . 101 to 011 . . . 110
+FSR/2 – 7/2 LSB 011 . . . 100 to 011 . . . 101

GND + 3/2 LSB 000 . . . 001 to 000 . . . 010
GND + 1/2 LSB 000 . . . 000 to 000 . . . 001
GND – 1/2 LSB 111 . . . 111 to 000 . . . 000
GND – 3/2 LSB 111 . . . 110 to 111 . . . 111

–FSR/2 + 5/2 LSB 100 . . . 010 to 100 . . . 011
–FSR/2 + 3/2 LSB 100 . . . 001 to 100 . . . 010
–FSR/2 + 1/2 LSB 100 . . . 000 to 100 . . . 001

NOTES

1

FSR is full-scale range is 5 V, with V

2

1 LSB = FSR/16384 = 610.4 µV (± 2.5 V – AD7899-3) with V

REF

= 2.5 V

= 2.5 V.

REF

TIMING AND CONTROL
Starting a Conversion

The conversion is initiated by applying a rising edge to the
CONVST signal. This places the track/hold into hold mode and
starts the conversion. The status of the conversion is indicated
by the dual function signal BUSY/EOC. The AD7899 can operate
in two conversion modes, EOC (End Of Conversion) mode and
BUSY mode. The operating mode is determined by the state of
CONVST at the end of the conversion.

Selecting a Conversion Clock

The AD7899 has an internal laser trimmed oscillator which can
be used to control the conversion process. Alternatively an external
clock source can be used to control the conversion process. The
highest external clock frequency allowed is 6.5 MHz. This means
a conversion time of 2.46 µs compared to 2.2 µs using the inter-
nal clock. However in some instances it may be useful to use an
external clock when high throughput rates are not required. For
example two or more AD7899s may be synchronized by using
the same external clock for all devices. In this way there is no
latency between output logic signals due to differences in the
frequency of the internal clock oscillators.

On the rising edge of CONVST the AD7899 will examine the
status of the CLKIN pin. If this pin is low it will use the internal
laser trimmed oscillator as the conversion clock. If the CLKIN pin
is high the AD7899 will wait for an external clock to be supplied
to this pin which will then be used as the conversion clock. The
first falling edge of the external clock should not happen for at
least 100 ns after the rising edge of CONVST to ensure correct
operation. Figure 5 shows how the BUSY/EOC output is synchro­nized to the CLKIN signal. Each conversion requires 16 clocks.
The result of the conversion is transferred to the output data
register on the falling edge of the 15th clock cycle. When the
internal clock is selected the status of the CLKIN pin is free to
change during conversion but the CLKIN setup and hold times
must be observed in order to ensure that the correct conversion
clock is used. The CLKIN pin can also be tied low permanently if
the internal conversion clock is to be used.

t

9

1 2 3 4 5 6 7 8 9 10 11121314 1516

CLKIN

t

11

CONVST

BUSY/EOC

RD

CS

Figure 5. Using an External Clock

–10–

REV. A

CLKIN

CONVST

BUSY/EOC

RD

CS

AD7899

t

10

t

9

t

1

t

EOC

t

2

t

CONV

t

8

t

3

t

ACQ

QUIET

TIME

t

5

t

4

DATA

THREE-STATE

Figure 6. Conversion Sequence Timing Diagram (EOC Mode)

t

10

t

9

CLKIN

CONVST

BUSY/EOC

DATA

RD

CS

t

1

THREE-STATE

t

CONV

Figure 7. Conversion Sequence Timing Diagram (BUSY Mode)

EOC Mode

The CONVST signal is normally high. Pulsing the CONVST low
will initiate a conversion on its rising edge. The state of the

CONVST signal is checked at the end of conversion. Since the
CONVST will be high when this happens the AD7899 BUSY/
EOC pin will take on its EOC function and bring the BUSY/EOC

line low for one clock period before returning high again. In this
mode the EOC can be tied to the RD and CS signals to allow
automatic reading of the conversion result if required. The timing
diagram for operation in EOC mode is shown in Figure 6.

BUSY Mode

The CONVST signal is normally low. Pulsing the CONVST
high will initiate a conversion on its rising edge. The state of the

CONVST signal is checked at the end of conversion. Since the
CONVST will be low when this happens the AD7899 BUSY/
EOC pin will take on its BUSY function will bring BUSY/EOC

low, indicating that the conversion is complete. BUSY/EOC will
remain low until the next rising edge of CONVST where BUSY/
EOC returns high. The timing diagram for operation in BUSY
mode is shown in Figure 7.

THREE-STATE

t

6

t

8

t

5

t

3

t

6

t

7

t

ACQ

QUIET

TIME

t

4

THREE-STATE

t

7

Continuous Conversion Mode

When the AD7899 is used with an external clock, connecting
the CLKIN and CONVST signals together will cause the AD7899
to continuously perform conversions. As each conversion com­pletes the BUSY/EOC pin will pulse low for one clock period
(EOC function) indicating that the conversion result is available.
Figure 8 shows the timing and control sequence of the AD7899
in Continuous Conversion Mode.

Reading Data from the AD7899

Data is read from the part via a 14-bit parallel data bus with
standard CS and RD signals. The CS and RD inputs are inter­nally gated to enable the conversion result onto the data bus.
The data lines DB0 to DB13 leave their high impedance state
when both CS and RD are logic low. Therefore CS may be
permanently tied logic low and the RD signal used to access the
conversion result if required. Figures 6 and 7 show a timing
specification called “Quiet Time.” This is the amount of time
which should be left after a read operation and before the next
conversion is initiated. The quiet time depends heavily on data
bus capacitance but a figure of 50 ns to 100 ns is typical, with a
worst case figure of 150 ns.

REV. A

–11–

AD7899

2 3 4 5 6 7 8 9 10 11 12 13 14

CONVST/

CLKIN

EOC

1

START OF NEW

CONVERSION

(INPUT SAMPLED)

Figure 8. Continuous Conversion Mode

Standby Mode Operation

The AD7899 has a Standby Mode whereby the device can be
placed in a low current consumption mode (5 µA typ). The
AD7899 is placed in Standby by bringing the logic input STBY
low. The AD7899 can be powered again up for normal opera­tion by bringing STBY logic high. The output data buffers are
still operational while the AD7899 is in Standby. This means
the user can still continue to access the conversion results while
the AD7899 is in standby. This feature can be used to reduce
the average power consumption in a system using low throughput
rates. To reduce the average power consumption, the AD7899
can be placed in standby at the end of each conversion sequence
and taken out of standby again prior to the start of the next
conversion sequence. The time it takes the AD7899 to come out
of standby is called the “wake up” time. This wake-up time will
limit the maximum throughput rate at which the AD7899 can
be operated when powering down between conversions. When
the AD7899 is used with the internal reference, the reference
capacitor will begin to discharge during standby. The voltage
remaining on the capacitor at wake-up time will depend upon
the standby time and hence affect the wake-up time. The mini­mum wake-up time is typically 2 µs. The maximum wake-up
time will be when the AD7899 has been in standby long enough
for the reference capacitor to fully discharge. The wake-up time
in this case will typically be 15 ms. The AD7899 will wake up in
approximately 1 µs when using an external reference, regardless
of sleep time.

When operating the AD7899 in a Standby mode between con­versions, the power savings can be significant. For example,
with a throughput rate of 10 kSPS and an external reference, the
AD7899 will be powered up for 4.2 µs out of every 100 µs (2 µs
for wake-up time and 2.2 µs for conversion time). Therefore, the
average power consumption drops to 80 mW × 4.2% or approxi­mately 3.36 mW.

AD7899 DYNAMIC SPECIFICATIONS

The AD7899 is specified and 100% tested for dynamic perfor­mance specifications as well as traditional dc specifications such
as Integral and Differential Nonlinearity. These ac specifications
are required for the signal processing applications such as phased
array sonar, adaptive filters, and spectrum analysis. These appli­cations require information on the ADC’s effect on the spectral
content of the input signal. Hence, the parameters for which the
AD7899 is specified include SNR, harmonic distortion, inter­modulation distortion, and peak harmonics. These terms are
discussed in more detail in the following sections.

15 16

CONVERSION

COMPLETE

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 (f

/2) excluding dc. SNR is dependent

S

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 14-bit converter, SNR = 86.04 dB.

Figure 9 shows a histogram plot for 8192 conversions of a dc
input using the AD7899 with 5 V supply. The analog input was
set at the center of a code transition. It can be seen that most of
the codes appear in one output bin, indicating very good noise
performance from the ADC.

7000

6000

5000

4000

3000

2000

1000

0

Figure 9. Histogram of 8192 Conversions of a DC Input

The output spectrum from the ADC is evaluated by applying a
sine wave signal of very low distortion to the analog input. A
Fast Fourier Transform (FFT) plot is generated from which the
SNR data can be obtained. Figure 10 shows a typical 4096 point
FFT plot of the AD7899 with an input signal of 100 kHz and a
sampling frequency of 400 kHz. The SNR obtained from this
graph is 80.5 dB. It should be noted that the harmonics are
taken into account when calculating the SNR.

–12–

REV. A

AD7899

FREQUENCY – Hz

–140

dB

0 50000

100000 150000 200000

–120

–100

–80

–60

–40

–20

0

0 2000

4000 16000

1.00

ADC – Code

–1.00

INL – LSB

6000 8000 10000 12000 14000

–0.50

0

0.50

0 2000

4000 16000

1.00

ADC – Code

–1.00

DNL – LSB

6000 8000 10000 12000 14000

–0.50

0

0.50

0

–20

fs = 400kHz

–40

–60

dB

–80

–100

–120

–140

0 50000

100000 150000 200000

FREQUENCY – Hz

fIN = 100kHz
SNR = 80.5dB

Figure 10. FFT Plot

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. 7 6

N =

6.02

(2)

The effective number of bits for a device can be calculated directly
from its measured SNR. Figure 11 shows a typical plot of effec­tive number of bits versus frequency for an AD7899.

second and third order terms are specified separately. The cal­culation of the intermodulation distortion is as 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 12 shows a typical
IMD plot for the AD7899.

Figure 12. IMD Plot

AC Linearity Plots

The plots in Figure 13 show typical DNL and INL for the
AD7899.

14

13

12

11

10

9

8

7

ENOB

6

5

4

3

2

1

0

0

100

INPUT FREQUENCY – kHz

1000 10000

–55ⴗC

+25ⴗC

+125ⴗC

Figure 11. Effective Numbers of Bits vs. Frequency

Intermodulation Distortion

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).

The AD7899 is tested using two input frequencies. In this case
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

REV. A

–13–

Figure 13. Typical DNL and INL Plots

AD7899

MICROPROCESSOR INTERFACING

The high-speed parallel interface of the AD7899 allows easy
interfacing to most DSPs and microprocessors. The AD7899
interface of the AD7899 consists of the data lines (DB0 to DB13),
CS, RD, and BUSY/EOC.

AD7899–ADSP-21xx Interface

Figure 14 shows an interface between the AD7899 and the
ADSP-21xx. The CONVST signal can be generated by the
ADSP-21xx or from some other external source. Figure 14 shows
the CS being generated by a combination of the DMS signal and
the address bus of the ADSP-21xx. In this way the AD7899 is
mapped into the data memory space of the ADSP-21xx.

The AD7899 BUSY/EOC line provides an interrupt to the
ADSP-21xx when the conversion is complete. The conversion
result can then be read from the AD7899 using a read operation.
The AD7899 is read using the following instruction

MR0 = DM(ADC)

where MR0 is the ADSP-21xx MR0 register and ADC is the
AD7899 address.

ADSP-21xx

ADDRESS

DECODE

CS

V

IN

RD

A0–A13

DMS

RD

AD7899–TMS320C5x Interface

Figure 15 shows an interface between the AD7899 and the
TMS320C5x. As with the previous interfaces, conversion can be
initiated from the TMS320C5x or from an external source and
the processor is interrupted when the conversion sequence is
completed. The CS signal to the AD7899 derived from the DS
signal and a decode of the address bus. This maps the AD7899
into external data memory. The RD signal from the TMS320 is
used to enable the ADC data onto the data bus. The AD7899 has
a fast parallel bus so there are no wait state requirements. The
following instruction is used to read the conversion results from
the AD7899:

IN D,ADC

where D is Data Memory address and ADC is the AD7899
address.

TMS320C5x

A0–A13

DS

RD

D0–D13

INTn

V

IN

DB0–DB13

AD7899

BUSY/EOC

CS

RD

ADDRESS

DECODE

DB0–DB13

AD7899

BUSY/EOC

CONVST

D8–D21

IRQn

DT1/F0

Figure 14. AD7899–ADSP-21xx Interface

CONVST

PA0

Figure 15. AD7899–TMS320C5x Interface

–14–

REV. A

OUTLINE DIMENSIONS

0.009 (0.229)

0.005 (0.127)

0.03 (0.762)

0.022 (0.558)

8°
0°

0.008 (0.203)

0.002 (0.050)

0.07 (1.79)

0.066 (1.67)

0.078 (1.98)

0.068 (1.73)

0.015 (0.38)

0.010 (0.25)

SEATING

PLANE

0.0256
(0.65)

BSC

0.311 (7.9)

0.301 (7.64)

0.212 (5.38)

0.205 (5.21)

28 15

141

0.407 (10.34)

0.397 (10.08)

PIN 1

Dimensions shown in inches and (mm).

28-Lead Small Outline

(R-28)

0.7125 (18.10)

0.6969 (17.70)

AD7899

28 15

PIN 1

0.0192 (0.49)

0.0118 (0.30)

0.0040 (0.10)

0.0500
(1.27)

BSC

0.0138 (0.35)

28-Lead Shrink Small Outline

141

0.1043 (2.65)

0.0926 (2.35)

SEATING
PLANE

(RS-28)

0.2992 (7.60)

0.2914 (7.40)

0.4193 (10.65)

0.3937 (10.00)

0.0125 (0.32)

0.0091 (0.23)

0.0291 (0.74)

0.0098 (0.25)

8ⴗ
0ⴗ

ⴛ 45ⴗ

0.0500 (1.27)

0.0157 (0.40)

AD7899–Revision History

Location Page

Data Sheet changed from REV. 0 to REV. A.

Edit to Timing page heading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Edit to Converter Details section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Edit to Figure 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

–15–

REV. A

C01365–0–6/01(A)

–16–

PRINTED IN U.S.A.