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AD8205 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD8205
Beschreibung Single-Supply 42 V System Difference Amplifier
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 13 Seiten
AD8205 Datasheet, Funktion
Data Sheet
FEATURES
Ideal for current shunt applications
High common-mode voltage range
−2 V to +65 V operating
−25 V to +75 V survival
Gain = 50 V/V
Wide operating temperature range:
−40°C to +125°C for Y and W grade
−40°C to +150°C for H grade
Bidirectional operation
Available in 8-lead SOIC
Qualified for automotive applications
EXCELLENT AC AND DC PERFORMANCE
15 µV/°C offset drift
30 ppm/°C gain drift
80 dB CMRR dc to 20 kHz
APPLICATIONS
High-side current sensing in:
Motor controls
Transmission controls
Diesel injection controls
Engine management
Suspension controls
Vehicle dynamic controls
DC-to-dc converters
GENERAL DESCRIPTION
The AD8205 is a single-supply difference amplifier for
amplifying small differential voltages in the presence of large
common-mode voltages. The operating input common-mode
voltage range extends from −2 V to +65 V. The typical single-
supply voltage is 5 V.
The AD8205 is offered in an 8-lead SOIC package and rated for
operation from −40°C to +125°C for the Y and W grade
models. The H grade version of the AD8205 is rated from
−40°C to +150°C.
Excellent dc performance over temperature keeps errors in the
measurement loop to a minimum. Offset drift is typically less
Single-Supply 42 V System
Difference Amplifier
AD8205
FUNCTIONAL BLOCK DIAGRAM
V+
6
+IN 8
–IN 1
5 OUT
AD8205
7 VREF1
NC 4
NC = NO CONNECT
2
GND
Figure 1.
3 VREF2
than 15 µV/°C, and gain drift is typically below 30 ppm/°C.
The output offset can be adjusted from 0.05 V to 4.8 V with a
5 V supply by using the VREF1 and VREF2 pins. With VREF1
attached to the V+ pin, and VREF2 attached to the GND pin, the
output is set at half scale. Attaching both pins to GND causes
the output to be unipolar, starting near ground. Attaching both
pins to V+ causes the output to be unipolar starting near V+.
Other offsets can be obtained by applying an external voltage to
the VREF1 and VREF2 pins.
Rev.D
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor 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 ©2004–2012 Analog Devices, Inc. All rights reserved.






AD8205 Datasheet, Funktion
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
AD8205
Figure 2. Metallization Diagram
–IN 1
8 +IN
GND 2 AD8205 7 VREF1
VREF2
3
TOP VIEW
(Not to Scale)
6
V+
NC 4
5 OUT
NC = NO CONNECT
Figure 3. Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
Mnemonic
1 −IN
2 GND
3 VREF2
4 NC
5 OUT
6 V+
7 VREF1
8 +IN
X
−206
−447
−432
N/A
444
444
456
203
Y
508
57
−457
N/A
−472
−203
434
509
Die size is 1170 µm by 1280 µm.
Die thickness is 13 mil.
Minimum passivation opening (minimum bond pad size) is
92 µm × 92 µm.
Passivation type is 8KA USG (Oxide) + 10KA Oxynitride.
Bond pad metal composition is 98.5% Al, 1% Si, and 0.5% Cu.
Backside potential is V+.
Rev.D | Page 5 of 12

6 Page









AD8205 pdf, datenblatt
Data Sheet
APPLICATIONS INFORMATION
A typical application for the AD8205 is high-side measurement
of a current through a solenoid for PWM control of the
solenoid opening. Typical applications include hydraulic
transmission control and diesel injection control.
Two typical circuit configurations are used for this type of
application.
HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE
SWITCH
In this case, the PWM control switch is ground referenced. An
inductive load (solenoid) is tied to a power supply. A resistive
shunt is placed between the switch and the load (see Figure 19).
An advantage of placing the shunt on the high side is that the
entire current, including the re-circulation current, can be
measured since the shunt remains in the loop when the switch
is off. In addition, diagnostics can be enhanced because shorts
to ground can be detected with the shunt on the high side.
In this circuit configuration, when the switch is closed, the
common-mode voltage moves down to near the negative rail.
When the switch is opened, the voltage reversal across the
inductive load causes the common-mode voltage to be held one
diode drop above the battery by the clamp diode.
5V
CLAMP
DIODE
INDUCTIVE
LOAD
42V
BATTERY
SHUNT
+IN VREF1 +VS OUT
AD8205
–IN GND VREF2 NC
SWITCH
NC = NO CONNECT
Figure 19. Low-Side Switch
HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE
SWITCH
This configuration minimizes the possibility of unexpected
solenoid activation and excessive corrosion (see Figure 20). In
this case, both the switch and the shunt are on the high side.
When the switch is off, this removes the battery from the load,
which prevents damage from potential shorts to ground, while
still allowing the recirculating current to be measured and
providing for diagnostics. Removing the power supply from the
load for the majority of the time minimizes the corrosive effects
that could be caused by the differential voltage between the load
and ground.
AD8205
When using a high-side switch, the battery voltage is connected
to the load when the switch is closed, causing the common-
mode voltage to increase to the battery voltage. In this case,
when the switch is opened, the voltage reversal across the
inductive load causes the common-mode voltage to be held one
diode drop below ground by the clamp diode.
5V
42V
BATTERY
SWITCH
SHUNT
CLAMP
DIODE
+IN VREF1 +VS OUT
AD8205
–IN GND VREF2 NC
INDUCTIVE
LOAD
NC = NO CONNECT
Figure 20. High-Side Switch
Another typical application for the AD8205 is as part of the
control loop in H-bridge motor control. In this case, the
AD8205 is placed in the middle of the H-bridge (see Figure 21)
so that it can accurately measure current in both directions by
using the shunt available at the motor. This is a better solution
than a ground referenced op amp because ground is not
typically a stable reference voltage in this type of application.
This instability in the ground reference causes the
measurements that could be made with a simple ground
referenced op amp to be inaccurate.
The AD8205 measures current in both directions as the
H-bridge switches and the motor changes direction. The output
of the AD8205 is configured in an external reference
bidirectional mode, see the Output Offset Adjustment section.
CONTROLLER
5V
MOTOR
SHUNT
+IN VREF1 +VS OUT
AD8205
–IN GND VREF2 NC
5V
2.5V
NC = NO CONNECT
Figure 21. Motor Control Application
Rev.D | Page 11 of 12

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