Isolated Voltage-Measurement with ±1V Input, Differential Output and Integrated DC/DC Converter

This product can be used in bidirectional high-voltage measurements. The output is fully isolated from the input side and can be used for applications such as high-voltage DC-DC converters, High-Voltage EV chargers, SMPS, 3 Phase motor drivers, inverters, etc. The board is built using the AMC3330 chip. This chip is a precision, isolated amplifier with a fully integrated, isolated DC/DC converter that allows single-supply operation from the low side of the device. The reinforced capacitive isolation barrier is certified according to VDE V 0884-11 and UL1577 and separates sections of the system that operate on different common-mode voltage levels and protect low-voltage domains from damage. The circuit senses high voltage in the range from -1V to 1V across resistor dividers R11, R4, R5, R8, and R12 and provides differential analog output Out-P and Out-N. The integrated isolated DC/DC converter allows the measurement of non-ground-referenced signals.

The board offers a differential analog output comprised of OUTP and OUTN pins. For differential input voltages (VINP – VINN) in the range from –1 V to 1 V, the device provides a linear response with a nominal gain of 2. For example, for a differential input voltage of 1 V, the differential output voltage (VOUTP – VOUTN) is 2 V. At zero input (INP shorted to INN), both pins output the same voltage, VCMout. For absolute differential input voltages greater than 1.0 V but less than 1.25 V, the differential output voltage continues to increase in magnitude but with reduced linearity performance.

Voltage Range and Divider Resistor Calculation

The board is optimized for 230V AC measurements, thus it can be modified for higher or lower voltage measurement range by altering the value of divider resistors R11, R4, R5, R8, R12. Current through resistor divider is 100uA, resulting in voltage drop on sense resistor R5 = 1V.

• For 230V-RMS Line Voltage (Peak Voltage 325V) R11=20K + R4=1.6M, R5 = 10K, R12 = 20K + R8=1.6M Tolerance 1%
• For 120V-RMS Line Voltage (Peak Voltage 170V) R11=25K + R4=820K, R5 = 10K, R12 = 25K + R8=820K Tolerance 1%

Connections and Other Important Details

• CN1: Pin 1 = DIAG, PIN 2 = No Use, Pin 3 = Op, Pin 4 = GND
• CN2: Pin 1 = VDD 5V DC In, Pin 2 = Output-P, Pin 3 = Output-N, Pin 4 = GND
• CN3: Pin 1 = Primary Input +P, Pin 2 = Primary Input -N
• D1: Power LED

Features

• Power Supply Input 5V DC (Range 3.3V to 5V)
• ±1-V input voltage range optimized for voltage measurements with a high input impedance
• Fixed gain: 2.0
• 6000-VPK reinforced isolation
• Low DC errors: – Gain error: ±0.2% (max) – Gain drift: ±45 ppm/°C (max) – Offset error: ±0.3 mV (max) – Offset drift: ±4 µV/°C (max) – Nonlinearity: ±0.02% (max)
• Common Mode Output 1.44V (Voltage Output at zero 1.44V)
• Clipping Differential Output Voltage +/-2.49V (VOUT = (VOUTP – VOUTN); |VIN| = |VINP – VINN| > VClipping)
• Output Short-circuit Current 14mA
• PCB Dimensions 53.98 x 19.69mm
• 4 x 2.5 mm Mounting Holes