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ADA4941-1 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADA4941-1
Beschreibung Single Supply Differential 18-Bit ADC Driver
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 24 Seiten
ADA4941-1 Datasheet, Funktion
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Single-ended-to-differential converter
Excellent linearity
Distortion −110 dBc @100 KHz for VO, dm = 2 V p-p
Low noise: 10.2 nV/√Hz, output-referred, G = 2
Extremely low power: 2.2 mA (3 V supply)
High input impedance: 24 MΩ
User-adjustable gain
High speed: 31 MHz, −3 dB bandwidth (G = +2)
Fast settling time: 300 ns to 0.005% for a 2 V step
Low offset: 0.8 mV max, output-referred, G = 2
Rail-to-rail output
Disable feature
Wide supply voltage range: 2.7 V to 12 V
Available in space-saving, 3 mm × 3 mm LFCSP
APPLICATIONS
Single-supply data acquisition systems
Instrumentation
Process control
Battery-power systems
Medical instrumentation
GENERAL DESCRIPTION
The ADA4941-1 is a low power, low noise differential driver for
ADCs up to 18 bits in systems that are sensitive to power. The
ADA4941-1 is configured in an easy-to-use, single-ended-to-
differential configuration and requires no external components
for a gain of 2 configuration. A resistive feedback network can
be added to achieve gains greater than 2. The ADA4941-1
provides essential benefits, such as low distortion and high
SNR, that are required for driving high resolution ADCs.
With a wide input voltage range (0 V to 3.9 V on a single 5 V
supply), rail-to-rail output, high input impedance, and a user-
adjustable gain, the ADA4941-1 is designed to drive single-
supply ADCs with differential inputs found in a variety of low
power applications, including battery-operated devices and
single-supply data acquisition systems.
Single-Supply, Differential
18-Bit ADC Driver
ADA4941-1
FUNCTIONAL BLOCK DIAGRAM
FB 1
REF 2
V+ 3
OUT+ 4
Figure 1.
8 IN
7 DIS
6 V–
5 OUT–
–60
–65
–70
–75
–80
–85
–90
–95
–100
–105
–110
–115
–120
–125
–130
–135
–140
0.1
HD3
HD2
HD2
HD3
1
10
VO = 6V p-p
VO = 2V p-p
100 1000
FREQUENCY (kHz)
Figure 2. Distortion vs. Frequency at Various Output Amplitudes
The ADA4941-1 is ideal for driving the 16-bit and 18-bit
PulSAR® ADCs such as the AD7687, AD7690, and AD7691.
The ADA4941-1 is manufactured on ADI’s proprietary second-
generation XFCB process, which enables the amplifier to
achieve 18-bit performance on low supply currents.
The ADA4941-1 is available in a small 8-lead LFCSP as well as a
standard 8-lead SOIC and is rated to work over the extended
industrial temperature range, −40°C to +125°C.
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. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2006–2009 Analog Devices, Inc. All rights reserved.






ADA4941-1 Datasheet, Funktion
ADA4941-1
ABSOLUTE MAXIMUM RATINGS
Table 4.
Parameter
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Power Dissipation
Storage Temperature Range
Operating Temperature Range
Lead Temperature (Soldering 10 sec)
Junction Temperature
Rating
12 V
See Figure 3
−65°C to +125°C
−40°C to +85°C
300°C
150°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 indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, θJA is
specified for a device soldered in the circuit board with its
exposed paddle soldered to a pad (if applicable) on the PCB
surface that is thermally connected to a copper plane, with zero
airflow.
Table 5. Thermal Resistance
Package Type
θJA θJC
8-Lead SOIC on 4-Layer Board
126 28
8-Lead LFCSP with EP on 4-Layer Board 83 19
Unit
°C/W
°C/W
Maximum Power Dissipation
The maximum safe power dissipation in the ADA4941-1
package is limited by the associated rise in junction temperature
(TJ) on the die. At approximately 150°C, which is the glass
transition temperature, the plastic changes its properties. Even
temporarily exceeding this temperature limit can change the
stresses that the package exerts on the die, permanently shifting
the parametric performance of the ADA4941-1. Exceeding a
junction temperature of 150°C for an extended period can
result in changes in the silicon devices potentially causing
failure.
The power dissipated in the package (PD) is the sum of the
quiescent power dissipation and the power dissipated in the
package due to the load drive for all outputs. The quiescent
power is the voltage between the supply pins (VS) times the
quiescent current (IS). The power dissipated due to the load
drive depends upon the particular application. For each output,
the power due to load drive is calculated by multiplying the load
current by the associated voltage drop across the device. The
power dissipated due to all of the loads is equal to the sum of
the power dissipation due to each individual load. RMS voltages
and currents must be used in these calculations.
Airflow increases heat dissipation, effectively reducing θJA. In
addition, more metal directly in contact with the package leads
from metal traces, through holes, ground, and power planes
reduces the θJA. The exposed paddle on the underside of the
package must be soldered to a pad on the PCB surface that is
thermally connected to a copper plane to achieve the specified θJA.
Figure 3 shows the maximum safe power dissipation in the
packages vs. the ambient temperature for the 8-lead SOIC
(126°C/W) and for the 8-lead LFCSP (83°C/W) on a JEDEC
standard 4-layer board. The LFCSP must have its underside
paddle soldered to a pad that is thermally connected to a PCB
plane. θJA values are approximations.
2.5
2.0
LFCSP
1.5
1.0
SOIC
0.5
0
–40 –20
0
20 40 60
80 100 120
AMBIENT TEMPERATURE (°C)
Figure 3. Maximum Power Dissipation vs. Temperature for a 4-Layer Board
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. A | Page 6 of 24

6 Page









ADA4941-1 pdf, datenblatt
ADA4941-1
0
–10
–20
–30
–40
www.datas50heet4u.com
–60
–70
–80
–90
–100
–110
0.001
0.01
+PSRR
–PSRR
0.1 1 10
FREQUENCY (MHz)
100 1000
Figure 29. Power Supply Rejection Ratio vs. Frequency
3.5
VPD = VS–
3.0
2.5 VS = ±5V
VS = +5V
2.0
VS = +3V
1.5
1.0
–40
–20
0
20 40 60 80 100 120
TEMPERATURE (°C)
Figure 30. Power Supply Current vs. Temperature
150
125
VOS_A2 = 10V
100 VOS_A2 = 5V
75
VOS_A2 = 3V
50
VOS_A1 10V
25
VOS_A1 = 3V
0
–40 –20
0
VOS_A1 = 5V
20 40 60 80
TEMPERATURE (°C)
100 120
Figure 31. Differential Output Offset Voltage vs. Temperature
0.18
±5V SUPPLIES, POSITIVE RAIL
0.16
0.14
±5V SUPPLIES, NEGATIVE RAIL
0.12
0.10 +5V SUPPLIES, POSITIVE RAIL
+5V SUPPLIES, NEGATIVE RAIL
0.08
0.06 +3V SUPPLIES, POSITIVE RAIL
0.04
–40
–20
+3V SUPPLIES, NEGATIVE RAIL
0 20 40 60 80 100
TEMPERATURE (°C)
120
Figure 32. Output Saturation Voltage vs. Temperature
2.5
ICC @ VS = ±5V
2.0 ICC @ VS = +3V
ICC @ VS = +5V
1.5
1.0
0.5
0
–0.5
0.6
0.8 1.0 1.2 1.4 1.6 1.8
DISABLE INPUT VOLTAGE WITH RESPECT TO VS– (V)
2.0
Figure 33. Power Supply Current vs. Disable Voltage
140
VOS1
MEAN = –8µV
120 STD. DEV = 47µV
VOS2
100 MEAN = 11µV
STD. DEV = 20µV
80 NO. OF UNITS = 611
60
40
20
0
OFFSET VOLTAGE (µV)
Figure 34. Differential Output Offset Distribution
Rev. A | Page 12 of 24

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