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AD8209 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD8209
Beschreibung Precision Difference Amplifier
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 16 Seiten
AD8209 Datasheet, Funktion
Data Sheet
FEATURES
±8000 V HBM ESD for shunt-based applications
AEC-Q100 qualified
EMI filters included
High common-mode voltage range
−2 V to +45 V operating
−24 V to +80 V survival
Buffered output voltage
Gain = 14 V/V
Low-pass filter (single-pole or two-pole)
Wide operating temperature range
−40°C to +125°C for WB grade
−40°C to +150°C for WH grade
Excellent ac and dc performance
±1 mV voltage offset
−5 ppm/°C typical gain drift
80 dB CMRR minimum dc to 10 kHz
Qualified for automotive applications
APPLICATIONS
High-side current sensing
Motor controls
Solenoid controls
Power management
Low-side current sensing
Diagnostic protection
GENERAL DESCRIPTION
The AD8209 is a single-supply difference amplifier ideal for
amplifying and low-pass filtering small differential voltages in the
presence of a large common-mode voltage. The input common-
mode voltage range extends from −2 V to +45 V at a single +5 V
supply. The AD8209 is qualified per AEC-Q100 specifications. The
amplifier offers enhanced input overvoltage and ESD protection,
and includes EMI filtering.
Automotive applications demand robust, precision components for
improved system control. The AD8209 provides excellent ac and dc
High Voltage,
Precision Difference Amplifier
AD8209
FUNCTIONAL BLOCK DIAGRAM
VS A1 A2
EMI
FILTER
IN+
EMI
FILTER
+
G=7
IN–
EMI
FILTER
AD8209
+
G=2
OUT
GND
Figure 1.
performance, minimizing errors in the application. Typical offset
and gain drift in the MSOP package are less than 5 µV/°C and
10 ppm/°C, respectively. The device also delivers a minimum
CMRR of 80 dB from dc to 10 kHz.
The AD8209 features an externally accessible 100 kΩ resistor at
the output of the preamplifier (A1), which can be used for low-
pass filtering and for establishing gains other than 14.
Rev. C
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AD8209 Datasheet, Funktion
AD8209
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
–IN 1
GND 2
A1 3
A2 4
AD8209
TOP VIEW
(Not to Scale)
8 +IN
7 VS
6 NC
5 OUT
NC = NO CONNECT
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Coordinates
Pin No. Mnemonic X
Y
1 −IN
−322 +563
2 GND
−321 +208
2 GND
−327 +339
3 A1
−321 −51
4 A2
−321 −214
5 OUT
+321 −388
6 NC
7 VS
+322 +363
8 +IN
+322 +561
Description
Inverting Input
Ground
Ground
Preamplifier (A1) Output
Buffer (A2) Input
Buffer (A2) Output
No Connect
Supply
Noninverting Input
Data Sheet
18
27
2
3
4
5
Figure 3. Metallization Photograph
Rev. C | Page 6 of 16

6 Page









AD8209 pdf, datenblatt
AD8209
Data Sheet
APPLICATIONS INFORMATION
HIGH-SIDE CURRENT SENSING
WITH A LOW-SIDE SWITCH
In load control configurations for high-side current sensing with a
low-side switch, the PWM-controlled switch is ground referenced.
An inductive load (solenoid) connects to a power supply/battery.
A resistive shunt is placed between the switch and the load (see
Figure 24). An advantage of placing the shunt on the high side
is that the entire current, including the recirculation current, is
monitored because the shunt remains in the loop when the switch
is off. In addition, shorts to ground can be detected with the shunt
on the high side, enhancing the diagnostics of the control loop. 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
BATTERY
+
SHUNT
+IN +VS NC OUT
OUTPUT
AD8209
SWITCH
–IN GND A1 A2
CF
NC = NO CONNECT
Figure 24. Low-Side Switch
In cases where a high-side switch is used for PWM control of the
load current in an application, the AD8209 can be used as shown
in Figure 25. The recirculation current through the freewheeling
diode (clamp diode) is monitored through the shunt resistor. In
this configuration, the common-mode voltage in the application
drops below GND when the FET is switched off. The AD8209
operates down to −2 V, providing an accurate current measurement.
5V
BATTERY
+
SWITCH
SHUNT
+IN +VS NC OUT
OUTPUT
AD8209
CLAMP
DIODE
INDUCTIVE
LOAD
–IN GND A1 A2
CF
NC = NO CONNECT
Figure 25. High-Side Switch
HIGH-RAIL CURRENT SENSING
In the high-rail current-sensing configuration, the shunt resistor is
referenced to the battery. High voltage is present at the inputs of
the current-sense amplifier. When the shunt is battery referenced,
the AD8209 produces a linear ground-referenced analog output.
Additionally, the AD8214 can be used to provide an overcurrent
detection signal in as little as 100 ns (see Figure 26). This feature is
useful in high current systems where fast shutdown in overcurrent
conditions is essential.
OVERCURRENT
DETECTION (<100ns)
5678
OUT GND NC –IN
AD8214
NC VREG +IN VS
4321
–IN
1
GND
2
A1
3
A2
4
CF
AD8209
+IN
8 5V
7 VS
NC
6
OUT
5
CLAMP
DIODE
SHUNT
INDUCTIVE
LOAD
+
BATTERY
SWITCH
Figure 26. Battery-Referenced Shunt Resistor
LOW-SIDE CURRENT SENSING
In systems where low-side current sensing is preferable, the
AD8209 provides a simple, high accuracy, integrated solution. In
this configuration, the AD8209 rejects ground noise and offers high
input to output linearity, regardless of the differential input voltage.
INDUCTIVE
LOAD
CLAMP
DIODE
SWITCH
BATTERY
SHUNT
5V
+IN +VS NC OUT
OUTPUT
AD8209
–IN GND A1 A2
CF
NC = NO CONNECT
Figure 27. Ground-Referenced Shunt Resistor
Rev. C | Page 12 of 16

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