SBASAY6 December 2024 AMC0236
PRODUCTION DATA
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The peak input voltage is 230V x √2 x 1.1 = 360V. The 200μA maximum cross-current requirement determines that the total impedance of the resistive divider is 1.8 MΩ. The impedance of the resistive divider is dominated by the top resistors (shown exemplary as R1 and R2 in Figure 8-1) and the voltage drop across RSNS can be neglected for a short time. The maximum allowed voltage drop per unit resistor is specified as 125V; therefore, the minimum number of unit resistors in the top portion of the resistive divider is 360V / 125V ≅ 3. The calculated unit value is 1.8MΩ / 3 = 600kΩ and the next closest value from the E96 series is 604kΩ.
Size RSNS such that the voltage drop at maximum input voltage (360V) equals the linear full-scale input voltage (VFSR) of the AMC0x36. RSNS is calculated as RSNS = VFSR / (VPeak – VFSR) × RTOP where RTOP is the total value of the top resistor string (3 × 604kΩ = 1.812MΩ). The resulting value for RSNS is 5.05kΩ. The next closest value from the E96 series is 4.99kΩ.
Table 8-2 summarizes the design of the resistive divider.
PARAMETER | VALUE |
---|---|
Unit resistor value, RTOP | 604kΩ |
Number of unit resistors in RTOP | 3 |
Sense resistor value, RSNS | 4.99kΩ |
Total resistance value (RTOP + RSNS) | 1.817MΩ |
Resulting current through resistive divider, ICROSS | 198.1μA |
Resulting full-scale voltage drop across sense resistor RSNS | 989mV |
Peak power dissipated in RTOP unit resistor | 23.7mW |
Total peak power dissipated in resistive divider | 71.3mW |