9.2.1.2 Detailed Design Procedure

The high-side power supply (AVDD) for the AMC1306 device is derived from the power supply of the upper gate driver. Further details are provided in the Power Supply Recommendations section.

The floating ground reference (AGND) is derived from one of the ends of the shunt resistor that is connected to the negative input of the AMC1306 (AINN). If a four-pin shunt is used, the inputs of the device are connected to the inner leads and AGND is connected to one of the outer shunt leads.

Use Ohm's Law to calculate the voltage drop across the shunt resistor (V_SHUNT) for the desired measured current: V_SHUNT = I × R_SHUNT.

Consider the following two restrictions to choose the proper value of the shunt resistor R_SHUNT:

• The voltage drop caused by the nominal current range must not exceed the recommended differential input voltage range: V_SHUNT ≤ ±250 mV
• The voltage drop caused by the maximum allowed overcurrent must not exceed the input voltage that causes a clipping output: |V_SHUNT| ≤ |V_Clipping|

The typically recommended RC filter in front of a ΔΣ modulator to improve signal-to-noise performance of the signal path is not required for the AMC1306. By design, the input bandwidth of the analog front-end of the device is limited as specified in the Electrical Characteristics table.

For modulator output bitstream filtering, a device from TI's TMS320F2807x family of low-cost microcontrollers (MCUs) or TMS320F2837x family of dual-core MCUs is recommended. These families support up to eight channels of dedicated hardwired filter structures that significantly simplify system level design by offering two filtering paths per channel: one providing high accuracy results for the control loop and one fast response path for overcurrent detection.