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

  • Rajkumar Sharma
  • 25 Views
  • easy
  • Tested
  • SKU: EL130694
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This project 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. The 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.

Note 1: Do not leave the analog inputs INP and INN of the project unconnected (floating) when the device is powered up on the high-side. If the device input is left floating, the bias current may generate a negative input voltage that exceeds the specified input voltage range and the output of the device will be invalid.
Note 2: It is advisable to use 1% tolerance for divider/voltage sense resistors.

Voltage Range and Divider Resistor Calculation

The project 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

Diagnostic Output and Fail-Safe Behaviour

The open-drain DIAG pin can be monitored to confirm the device is operational, and that the output voltage is valid. During power-up, the DIAG pin is actively held low until the high-side supply is in regulation and the device operates properly. The DIAG pin is actively pulled low if:

  • The low-side does not receive data from the high-side (for example, because of a loss of power on the high side). The amplifier outputs are driven to negative full-scale.
  • The high-side DC/DC output voltage (DCDC_OUT) or the high-side LDO output voltage (HLDO_OUT) drop below their respective undervoltage detection thresholds VDCDCUV and VHLDOUV as specified in the Electrical Characteristics table. In this case, the low-side may still receive data from the high-side but the data may not be valid. The amplifier outputs are driven to negative full-scale. During normal operation, the DIAG pin is in a high-impedance state. Connect the DIAG pin to a pull-up supply through a resistor or leave open if not used.

Schematic

Parts List

NOQNTYREFDECMANUFACTURESUPPLIERPART NO
12CN1,CN24 PIN MALE HEADER PITCH 2.54MMWURTHDIGIKEY732-5317-ND
21CN32 PIN SCREW TERMINAL PITCH 5.08MMPHOENIXDIGIKEY277-1247-ND
31C11nF/16V CERAMIC SMD SIZE 0805YAGEO/MURATADIGIKEY
41C21uF/25V CERAMIC SMD SIZE 0805YAGEO/MURATADIGIKEY
52C4,C90.1uF/50V CERAMIC SMD SIZE 0805YAGEO/MURATADIGIKEY
68R1,R2,C5,R6,C6,R7,R10,C11DNPDO NOT INSTALL
72C3,C70.1uF/50V CERAMIC SMD SIZE 1206YAGEO/MURATADIGIKEY
81C81nF/25V CERAMIC SMD SIZE 1206YAGEO/MURATADIGIKEY
91C1010uF/25V SMD SIZE 1206YAGEO/MURATADIGIKEY
101C1210nF/50V SMD SIZE 0805YAGEO/MURATADIGIKEY
111D1LED RED SMD SIZE 0805OSRAMDIGIKEY475-1278-1-ND
121R347K 5% SMD SIZE 0805YAGEO/MURATADIGIKEY
132R4,R81.6M 1% SMD SIZE 0805YAGEO/MURATADIGIKEY
141R510K 1% SMD SIZE 1206 OR 2512YAGEO/MURATADIGIKEY
151R91K 5% SMD SIZE 0805YAGEO/MURATADIGIKEY
162R11,R1220K 1% SMD SIZE 0805YAGEO/MURATADIGIKEY
171U1AMC3330TIDIGIKEY296-AMC3330QDWERQ1TR-ND
181U2TLV6001IDBVRTIDO NOT INSTALL

Connections

Output

Application Example



Gerber View

Photos

 

Video

AMC3330 Datasheet

amc3330

PCB

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