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The SMD Current Sense Resistor is a surface-mounted (SMD) type of low-resistance precision resistor, manufactured using alloy resistance technology or thick-film process. It is suitable for automated surface-mount production and is the preferred solution for current detection in current consumer electronics, lithium battery protection boards (BMS), power tools, drones, laptops, server power supplies, and other products. Compared to plug-in type, the surface-mount sampling resistor has advantages such as small size, light weight, no lead inductance, suitability for high frequency, good consistency, and high production efficiency. RST Electric also offers various types of Current Sense Resistors. Please come and consult for purchase!
Alloy resistors (Metal Strip or Metal Foil) are made by stamping alloy materials such as manganese-copper, nickel-copper, or iron-chromium-aluminum into flat shapes. The two ends are either welded or directly formed into terminal electrodes, and then a protective layer is applied. This type of structure has extremely low resistance (0.2 mΩ to 10 mΩ), extremely low temperature drift (±20 to ±50 ppm/℃), and high power density (such as 2512 packages can achieve 2W to 5W). Thick film surface mount sampling resistors use printed resistor paste on a ceramic substrate, but their temperature drift and long-term stability are not as good as alloy resistors. Therefore, alloy types are more commonly used in high-precision applications. Common package sizes include 0805, 1206, 2010, 2512, 2726, 2728, etc. The larger the number, the greater the power. A ±1% accuracy is standard, while ±0.5% and ±0.1% are used for high-precision battery management. Four-terminal (Kelvin) surface mount sampling resistors (such as 2728 packaging) further improve measurement accuracy and eliminate the influence of contact resistance at the terminal electrodes.
Smartphone charging current detection (in conjunction with fast charging protocol), battery measurement of TWS earphone charging case, overcurrent protection of electric tool battery pack, current feedback for server CPU core power supply, current monitoring of drone battery power, current detection of each string of batteries in BMS, etc. Key points for selecting SMD Current Sense Resistor:
1) The voltage drop generated by the product of rated current and resistance value should be within the effective range of ADC;
2) Power reduction curve: SMD resistors rely on PCB copper foil for heat dissipation, and require sufficient pads and copper foil area;
3) Inductance: For MHz-level switching current detection, the inductance of alloy resistors is usually lower than 2nH, while thick film resistors have slightly higher inductance;
4) Thermoelectric effect: For micro current detection (such as mAh level), the thermoelectric effect at the copper-alloy connection point will cause zero drift, and low thermoelectric effect materials should be selected.
