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AD8208WBRMZ データシート(PDF) 11 Page - Analog Devices |
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AD8208WBRMZ データシート(HTML) 11 Page - Analog Devices |
11 / 16 page AD8208 Rev. A | Page 11 of 16 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 25). 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. GND NC –IN +IN A1 VS A2 OUT AD8208 5V INDUCTIVE LOAD SWITCH SHUNT CLAMP DIODE BATTERY NC = NO CONNECT CF OUTPUT + – Figure 25. Low-Side Switch In cases where a high-side switch is used for PWM control of the load current in an application, the AD8208 can be used as shown in Figure 26. 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 AD8208 operates down to −2 V, providing an accurate current measurement. GND NC –IN +IN A1 VS A2 OUT AD8208 5V INDUCTIVE LOAD SWITCH SHUNT CLAMP DIODE BATTERY NC = NO CONNECT CF OUTPUT + – Figure 26. 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 AD8208 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 27). This feature is useful in high current systems where fast shutdown in overcurrent conditions is essential. AD8214 INDUCTIVE LOAD SWITCH CLAMP DIODE BATTERY SHUNT CF 5V –IN NC GND OVERCURRENT DETECTION (<100ns) OUT VS +IN VREG NC –IN GND A1 A2 +IN VS NC OUT AD8208 1 2 3 4 8 7 6 5 8 7 6 5 1 2 3 4 + – Figure 27. Battery-Referenced Shunt Resistor LOW-SIDE CURRENT SENSING In systems where low-side current sensing is preferable, the AD8208 provides a simple, high accuracy, integrated solution. In this configuration, the AD8208 rejects ground noise and offers high input to output linearity, regardless of the differential input voltage. GND NC –IN +IN A1 VS A2 OUT AD8208 5V INDUCTIVE LOAD SWITCH SHUNT CLAMP DIODE BATTERY NC = NO CONNECT CF OUTPUT Figure 28. Ground-Referenced Shunt Resistor |
同様の部品番号 - AD8208WBRMZ |
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同様の説明 - AD8208WBRMZ |
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