As a key component in circuit design, the core characteristics of low resistance sampling resistors directly determine the accuracy and reliability of current detection. The following are its main characteristics and technical points:
Ultra low resistance and high precision
Resistance range: usually in the milliohm range (such as 0.1m Ω~10m Ω), or even lower (such as 0.01m Ω), to reduce the impact of its own voltage drop on the circuit.
Accuracy requirement: High precision of ± 0.5%~± 1% is required to avoid amplification of current measurement errors due to resistance deviation (especially in high-precision power or battery management systems).
Low Temperature Coefficient (TCR)
Stability: The lower the TCR value (such as ± 50ppm/° C or lower), the smaller the change in resistance value with temperature, ensuring consistency of current detection over a wide temperature range.
Key scenarios: Suitable for high temperature environments (such as automotive electronics, industrial equipment) or applications with large temperature differences.
High rated power and heat dissipation design
Power carrying capacity: It needs to support high power (such as 1W~5W or even higher) to avoid resistance drift or damage caused by overheating.
Heat dissipation optimization: Using special packaging (such as TO-220, SMD large-size) or metal substrates to improve heat dissipation efficiency and maintain long-term stability.
Low parasitic inductance and parasitic capacitance
High frequency characteristics: extremely low parasitic parameters (such as inductance<1nH), avoiding oscillation or noise in high-speed switching circuits (such as DC-DC converters, inverters).
Signal integrity: Sampling high-frequency currents is particularly important to reduce signal distortion.
High reliability and durability
Material selection: Commonly used manganese copper alloy, nickel chromium alloy or thick film resistors, balancing low resistance and high stability.
Resistance to mechanical stress: The packaging design needs to resist vibration and impact (such as in automotive applications) to avoid changes in resistance.
Small size and integration trend
Modern demand: SMD packages (such as 0805, 2512) meet high-density PCB design while maintaining low resistance performance.
Cost balance: Small size may sacrifice some heat dissipation capacity, which needs to be balanced according to the application.
Low voltage coefficient
Voltage sensitivity: A low voltage coefficient means that the resistance value is less affected by voltage, avoiding measurement deviation caused by self heating effect under high current.
Application adaptability
Current range: Select the resistance value based on the target current (such as 1mV voltage drop corresponding to 1A current at 1m Ω for ADC sampling).
Protection function: Some designs integrate a fuse mechanism to prevent short circuits from damaging the secondary circuit.
The core of low resistance sampling resistors lies in balancing accuracy, power, and parasitic parameters, while meeting the temperature, mechanical, and electrical requirements of specific scenarios. When designing, it is necessary to comprehensively select based on circuit topology, current level, and environmental conditions to ensure the accuracy of current detection and system reliability.