SBASAQ0A March 2023 – December 2024 AMC23C15-Q1
PRODUCTION DATA
The value of the shunt resistor in this example is 1 mΩ, determined by the internal 60-mV reference of the AMC23C15-Q1 and the desired 60-A short-circuit detection threshold.
At the desired 25-A overcurrent detection level, the voltage drop across the shunt resistor is 1 mΩ × 25 A = 25 mV. The positive-going trip threshold of window comparator 1 is VREF + VHYS, where VHYS is 4 mV as specified in the Electrical Characteristics table, and VREF is the voltage across R1 that is connected between the REF and GND1 pins. R1 is calculated as (VTRIP – VHYS) / IREF = (25 mV – 4 mV) / 100 μA = 210 Ω and matches a value from the E96 series (1% accuracy).
A 10-Ω, 1-nF RC filter (R5, C6) is placed at the input of the comparator to filter the input signal and reduce noise sensitivity. This filter adds 10 Ω × 1 nF = 10 ns of propagation delay that must be considered when calculating the overall response time of the protection circuit. Larger filter constants are preferable to increase noise immunity if the system can tolerate the additional delay.
Table 7-2 summarizes the key parameters of the design.
PARAMETER | VALUE |
---|---|
Reference resistor value (R1) | 210 Ω |
Reference capacitor value (C5) | 100 nF |
Reference voltage | 21 mV |
Reference voltage settling time (to 90% of final value) | 50 μs |
Overcurrent trip threshold (rising) | 25 mV / 25.0 A |
Overcurrent trip threshold (falling) | 21 mV / 21 A |
Short-circuit current trip threshold (rising) | 64 mV / 64 A |
Short-circuit current trip threshold (falling) | 60 mV / 60.0 A |