ad7742 Analog Devices, Inc., ad7742 Datasheet

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ad7742

Manufacturer Part Number
ad7742
Description
Single And Multichannel, Synchronous Voltage-to-frequency Converters
Manufacturer
Analog Devices, Inc.
Datasheet
a
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
GENERAL DESCRIPTION
The AD7741/AD7742 are a new generation of synchronous
voltage-to-frequency converters (VFCs). The AD7741 is a
single-channel version in an 8-lead package (SOIC/DIP) and the
AD7742 is a multichannel version in a 16-lead package (SOIC/
DIP). No user trimming is required to achieve the specified
performance.
The AD7741 has a single buffered input whereas the AD7742
has four buffered inputs that may be configured as two fully-
differential inputs or three pseudo-differential inputs. Both parts
include an on-chip +2.5 V bandgap reference that provides the
user with the option of using this internal reference or an exter-
nal reference.
REV. 0
FEATURES
AD7741: One Single-Ended Input Channel
AD7742: Two Differential or Three Pseudo-Differential
Integral Nonlinearity of 0.012% at f
Single +5 V Supply Operation
Buffered Inputs
Programmable Gain Analog Front-End
On-Chip +2.5 V Reference
Internal/External Reference Option
Power Down to 35 A Max
Minimal External Components Required
8-Lead and 16-Lead DIP and SOIC Packages
APPLICATIONS
Low Cost Analog-to-Digital Conversion
Signal Isolation
Input Channels
(AD7742) and at f
OUT
(Max) = 1.35 MHz (AD7741)
OUT
(Max) = 2.75 MHz
Single and Multichannel, Synchronous
Voltage-to-Frequency Converters
The AD7741 has a single-ended voltage input range from 0 V
to REFIN. The AD7742 has a differential voltage input range
from –V
supply consuming typically 6 mA, and also contain a power-
down feature that reduces the current consumption to less than
35 A.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
GAIN
V
V
V
V
IN
IN
IN
IN
A1
A0
1
2
3
4
V
IN
REF
INPUT
MUX
V
to +V
GND
DD
FUNCTIONAL BLOCK DIAGRAMS
V
X1
DD
CLKIN
GENERATION
X1/X2
REF
REFIN/OUT
CLOCK
CLKIN
GENERATION
World Wide Web Site: http://www.analog.com
. Both parts operate from a single +5 V
CLKOUT
VOLTAGE-TO-
MODULATOR
FREQUENCY
CLOCK
UNI/BIP
CLKOUT
VOLTAGE-TO-
MODULATOR
FREQUENCY
AD7741/AD7742
REFERENCE
+2.5V
AD7742
REFIN
GND
© Analog Devices, Inc., 1999
AD7741
POWER-DOWN
REFOUT
POWER-DOWN
LOGIC
PD
LOGIC
PD
REFERENCE
+2.5V
f
OUT
f
OUT

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ad7742 Summary of contents

Page 1

... The AD7741 has a single-ended voltage input range from REFIN. The AD7742 has a differential voltage input range from –V REF supply consuming typically 6 mA, and also contain a power- down feature that reduces the current consumption to less than 35 A. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. ...

Page 2

AD7741–SPECIFICATIONS 2 Parameter DC PERFORMANCE Integral Nonlinearity 200 kHz CLKIN MHz CLKIN f = 6.144 MHz CLKIN Offset Error Gain Error 3 Offset Error Drift 3 Gain Error Drift 3 Power Supply Rejection ...

Page 3

... V or more negative than +0 –3– AD7741/AD7742 = +2 6.144 MHz; all specifications T CLKIN Max Units Conditions/Comments 5 0.015 % of Span 0.015 % of Span 0.015 % of Span 40 mV Unipolar Mode 40 mV Bipolar Mode +2 Span Unipolar Mode +2 ...

Page 4

... 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 AD7741/AD7742 features proprietary ESD protection circuitry, permanent dam- age may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality ...

Page 5

... Frequency Output. This pin provides the output of the synchronous VFC. OUT REV. 0 AD7741 PIN FUNCTION DESCRIPTION PIN CONFIGURATION OUT AD7741 GND TOP VIEW CLKOUT (Not to Scale) CLKIN 4 5 REFIN/OUT –5– AD7741/AD7742 . This input is buffered so it REF ...

Page 6

... Gain Select input that controls whether the gain on the analog front-end X2 Active Low Power-Down pin. When this input is low, the part enters power-down mode where it typi- cally consumes current. AD7742 PIN FUNCTION DESCRIPTION the negative input of a truly-differential input pair with respect ...

Page 7

... The four analog inputs (V range from +0 range and is relative to the GND pin. In the case of the AD7742 multichannel part, a differential multiplexer switches one of the differential input channels to the VFC modulator. The multiplexer is controlled by two pins, A1 and A0. See Table I for channel configurations. ...

Page 8

... GAIN and UNI/BIP pins. The transfer function for the AD7741 is shown in Figure 3. Figure 4 shows the AD7742 transfer function for unipolar input range configuration while the AD7742 transfer function for bipolar input range configuration is shown in Figure 5. ...

Page 9

... The maximum recommended load on this pin is one CMOS load. When using a crystal to generate the AD7741/ AD7742 clock it may be desirable to then use this clock as the clock source for the system. In this case it is recommended that the CLKOUT signal be buffered with a CMOS buffer before being applied to the rest of the circuit ...

Page 10

... AD7741/AD7742 APPLICATIONS The basic connection diagram for the part is shown in Figure 9. In the connection diagram shown, the AD7742 analog inputs are configured as fully differential, bipolar inputs with a gain quartz crystal provides the master clock source for the part. It may be necessary to connect capacitors (C1 and C2 in the diagram) on the crystal to ensure that it does not oscillate at over- tones of its fundamental operating frequency ...

Page 11

... The analog ground plane should be allowed to run under the AD7742 to avoid noise coupling. The power supply lines to the AD7742 should use as large a trace as pos- sible to provide low impedance paths and reduce the effects of glitches on the power supply line. Fast switching signals like ...

Page 12

... AD7741/AD7742 8-Lead Plastic DIP (N-8) 0.430 (10.92) 0.348 (8.84 0.280 (7.11) 0.240 (6.10 0.325 (8.25) PIN 1 0.100 (2.54) 0.300 (7.62) BSC 0.060 (1.52) 0.210 0.015 (0.38) (5.33) MAX 0.130 0.160 (4.06) (3.30) MIN 0.115 (2.93) 0.022 (0.558) 0.070 (1.77) SEATING PLANE 0.014 (0.356) 0.045 (1.15) 16-Lead Plastic DIP (N-16) 0.840 (21.34) 0.745 (18.92 0.280 (7.11) 0.240 (6.10 PIN 1 ...

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