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AD7742 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD7742
Beschreibung Single and Multichannel/ Synchronous Voltage-to-Frequency Converters
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 12 Seiten
AD7742 Datasheet, Funktion
a
Single and Multichannel, Synchronous
Voltage-to-Frequency Converters
AD7741/AD7742
FEATURES
AD7741: One Single-Ended Input Channel
AD7742: Two Differential or Three Pseudo-Differential
Input Channels
Integral Nonlinearity of 0.012% at fOUT(Max) = 2.75 MHz
(AD7742) and at fOUT(Max) = 1.35 MHz (AD7741)
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
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.
FUNCTIONAL BLOCK DIAGRAMS
VDD REFIN/OUT
PD
VIN X1
+2.5V
REFERENCE
VOLTAGE-TO-
FREQUENCY
MODULATOR
POWER-DOWN
LOGIC
fOUT
CLOCK
GENERATION
AD7741
CLKIN CLKOUT
GND
GAIN
VIN1
VIN2
VIN3
VIN4
A1
A0
VDD UNI/BIP
PD
INPUT
MUX
X1/X2
AD7742
VOLTAGE-TO-
FREQUENCY
MODULATOR
POWER-DOWN
LOGIC
fOUT
CLOCK
GENERATION
+2.5V
REFERENCE
GND CLKIN CLKOUT REFIN REFOUT
The AD7741 has a single-ended voltage input range from 0 V
to REFIN. The AD7742 has a differential voltage input range
from –VREF to +VREF. Both parts operate from a single +5 V
supply consuming typically 6 mA, and also contain a power-
down feature that reduces the current consumption to less than
35 µA.
REV. 0
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: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999






AD7742 Datasheet, Funktion
AD7741/AD7742
Pin No.
1
2
Mnemonic
fOUT
VDD
3 GND
4–5 A1, A0
6 CLKOUT
7 CLKIN
8 UNI/BIP
9 REFOUT
10 REFIN
11 VIN1
12 VIN2
13 VIN3
14 VIN4
15 GAIN
16 PD
AD7742 PIN FUNCTION DESCRIPTION
Function
Frequency Output. This pin provides the output of the synchronous VFC.
Power Supply Input. These parts can be operated from +4.75 V to +5.25 V and the supply should be
adequately decoupled to GND.
Ground reference point for all circuitry on the part.
Address Inputs used to select the input channel configuration.
External Clock Output. When the master clock for the device is a crystal, the crystal is connected be-
tween CLKIN and CLKOUT. When an external clock is applied to CLKIN, the CLKOUT pin
provides an inverted clock signal. This clock should be buffered if it is to be used as a clock source
elsewhere in the system.
External Clock Input. The master clock for the device can be provided in the form of a crystal or an
external clock. A crystal may be tied across the CLKIN and CLKOUT pins. Alternatively, the CLKIN
pin may be driven by a CMOS-compatible clock and CLKOUT left unconnected. The frequency of the
master clock may be as high as 6 MHz.
Control input which determines whether the device operates with differential bipolar analog input
signals or differential unipolar analog input signals.
2.5 V Voltage Reference Output. This can be tied directly to REFIN. It may also be used as a reference
to other parts of the system provided it is buffered first.
This is the Reference Input to the core of the VFC and defines the span of the VFC. A 2.5 V reference
is required at this pin. This may be provided by connecting it directly to REFOUT or by using a preci-
sion external reference (e.g., REF192).
Buffered Analog Input Channel 1. This is either a pseudo-differential input with respect to VIN4 or it is
the positive input of a truly-differential input pair with respect to VIN2.
Buffered Analog Input Channel 2. This is either a pseudo-differential input with respect to VIN4 or it is
the negative input of a truly-differential input pair with respect to VIN1.
Buffered Analog Input Channel 3. This is the positive input of a truly-differential input pair with re-
spect to VIN4.
Buffered Analog Input Channel 4. This is either the common for pseudo-differential input with respect
to VIN1 or VIN2 or it is the negative input of a truly-differential input pair with respect to VIN3.
Gain Select input that controls whether the gain on the analog front-end is X1 or X2.
Active Low Power-Down pin. When this input is low, the part enters power-down mode where it typi-
cally consumes 25 µA of current.
PIN CONFIGURATION
fOUT 1
16 PD
VDD 2
15 GAIN
GND 3
14 VIN4
A1 4 AD7742 13 VIN3
TOP VIEW
A0 5 (Not to Scale) 12 VIN2
CLKOUT 6
11 VIN1
CLKIN 7
10 REFIN
UNI/BIP 8
9 REFOUT
–6– REV. 0

6 Page









AD7742 pdf, datenblatt
AD7741/AD7742
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Plastic DIP
(N-8)
0.430 (10.92)
0.348 (8.84)
85
0.280 (7.11)
0.240 (6.10)
14
PIN 1
0.100 (2.54)
0.325 (8.25)
0.300 (7.62)
BSC
0.060 (1.52)
0.210
(5.33)
MAX
0.015 (0.38)
0.130
0.195 (4.95)
0.115 (2.93)
0.160 (4.06)
(3.30)
0.115 (2.93)
MIN
0.015 (0.381)
0.022 (0.558) 0.070 (1.77) SEATING
0.014 (0.356) 0.045 (1.15) PLANE
0.008 (0.204)
16-Lead Plastic DIP
(N-16)
0.840 (21.34)
0.745 (18.92)
16 9 0.280 (7.11)
1 8 0.240 (6.10)
PIN 1
0.060 (1.52)
0.325 (8.25)
0.300 (7.62)
0.210 (5.33)
0.015 (0.38)
MAX
0.130
0.160 (4.06)
(3.30)
0.115 (2.93)
MIN
0.022 (0.558) 0.100 0.070 (1.77) SEATING
0.014 (0.356)
(2.54)
BSC
0.045 (1.15)
PLANE
0.195 (4.95)
0.115 (2.93)
0.015 (0.381)
0.008 (0.204)
8-Lead SO
(R-8)
0.1968 (5.00)
0.1890 (4.80)
8
0.1574 (4.00)
0.1497 (3.80) 1
5
0.2440 (6.20)
4 0.2284 (5.80)
PIN 1
0.0500 (1.27)
BSC
0.0196 (0.50)
0.0099 (0.25) ؋ 45؇
0.102 (2.59)
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
0.094 (2.39)
0.0192 (0.49)
0.0138 (0.35)
8؇
0.0098 (0.25) 0؇
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
16-Lead Narrow Body SO
(R-16A)
0.3937 (10.00)
0.3859 (9.80)
0.1574 (4.00) 16
0.1497 (3.80)
1
9 0.2440 (6.20)
0.2284 (5.80)
8
PIN 1 0.050 (1.27) 0.0688 (1.75)
BSC
0.0532 (1.35)
0.0196
0.0099
((00..5205))؋
45؇
0.0098 (0.25)
0.0040 (0.10)
8؇
0.0192 (0.49)
0.0138 (0.35)
SEATING
PLANE
0.0099 (0.25) 0؇
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
–12–
REV. 0

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