Datasheet AD8211 (Analog Devices) - 12

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AD8211 Data Sheet APPLICATIONS INFORMATION OVERCURRENT HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE DETECTION (<100ns) SWITCH 5 6 7 8
In such load control configurations, the PWM-controlled
OUT GND NC –IN AD8214
switch is ground referenced. An inductive load (solenoid) is tied
NC V
to a power supply. A resistive shunt is placed between the switch
REG +IN VS 4 3 2 1
and the load (see Figure 25). An advantage of placing the shunt on the high side is that the entire current, including the recirculation current, can be measured because 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
1 3 2 3 1 V GND IN+ OUT
closed, the common-mode voltage moves down to near the negative rail. When the switch is opened, the voltage reversal
SHUNT AD8211
across the inductive load causes the common-mode voltage to
CLAMP DIODE VIN– V+
be held one diode drop above the battery by the clamp diode.
5 4 4 5 INDUCTIVE BATTERY LOAD 5V INDUCTIVE LOAD 1 3 2 3 1 SWITCH CLAMP V GND IN+ OUT DIODE
5
SHUNT AD8211
02 4-
BATTERY
682 0
VIN– V+
Figure 26. Battery Referenced Shunt Resistor
5 4 4 5 SWITCH LOW-SIDE CURRENT SENSING 5V
-024 In systems where low-side current sensing is preferred, the 24 068 AD8211 provides an integrated solution with great accuracy. Figure 25. Low-Side Switch Ground noise is rejected, CMRR is typically higher than 90 dB,
HIGH-SIDE CURRENT SENSING
and output linearity is not compromised, regardless of the input differential voltage. In this configuration, the shunt resistor is referenced to the battery. High voltage is present at the inputs of the current sense
INDUCTIVE
amplifier. In this mode, the recirculation current is again measured
LOAD 1 3 2 3 1 CLAMP V GND OUT
and shorts to ground can be detected. When the shunt is battery
DIODE IN+
referenced, the AD8211 produces a linear ground referenced,
AD8211 BATTERY
analog output. An AD8214 can also provide an overcurrent
SWITCH VIN– V+
detection signal in as little as 100 ns. This feature is useful in
5 4 4 5
high current systems where fast shutdown in overcurrent
5V
conditions is essential.
SHUNT
6 -02 4 82 06 Figure 27. Ground Referenced Shunt Resistor Rev. C | Page 12 of 13 Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION APPLICATION NOTES OUTPUT LINEARITY APPLICATIONS INFORMATION HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE SWITCH HIGH-SIDE CURRENT SENSING LOW-SIDE CURRENT SENSING OUTLINE DIMENSIONS ORDERING GUIDE AUTOMOTIVE PRODUCTS