IN Brief:
- SDR01 provides 0.33W rated power in the 1005 metric, or 0402 imperial, package size.
- The resistors maintain the full rating to a terminal temperature of 125°C and include AEC-Q200-qualified variants.
- ±1% devices provide ±100ppm/°C TCR from 10Ω to 2.2MΩ, supporting compact high-reliability designs.
ROHM has introduced the SDR01 family of high anti-surge thick-film chip resistors with a rated power of 0.33W in the 1005 metric, or 0402 imperial, package size. The components are intended for densely populated automotive, industrial, consumer, and AI-server circuits where board area, continuous dissipation, and resistance to short-duration electrical stress all have to be considered together.
An 0402 resistor occupies roughly 1.0mm by 0.5mm, making higher continuous power handling principally a thermal-design problem. ROHM says it revised the resistive element and electrode structures to increase the rating while retaining the surge performance expected from the SDR product family.
The SDR01 maintains its 0.33W rating up to a terminal temperature of 125°C. Terminal temperature is the temperature measured at the component termination rather than the surrounding air, which puts PCB layout directly into the power-rating calculation because heat has to leave the resistor through its electrodes, pads, copper, and board structure.
A resistor may therefore carry a 0.33W catalogue rating without safely dissipating that power in every layout. Pad geometry, copper area, board thickness, neighbouring components, airflow, enclosure temperature, and heat from nearby semiconductors all affect the thermal conditions at the termination.
ROHM specifies an operating-temperature range of -55°C to +155°C, while current SDR01 product listings include AEC-Q200-qualified automotive-grade devices. The F-tolerance version provides ±1% resistance tolerance across a 1Ω to 2.2MΩ range, with ±100ppm/°C TCR applying from 10Ω to 2.2MΩ. Designers need to check the individual resistance value because TCR limits differ at the bottom of the range.
Temperature coefficient describes how resistance changes as temperature moves away from the reference condition. In a compact circuit with higher local power density, self-heating and heat from adjacent components can make that characteristic relevant even when the resistor is not being used as a precision measurement element.
Surge endurance addresses a separate stress mechanism. Power rails, switching circuits, interfaces, and automotive electrical systems can subject resistors to short pulses well above their normal continuous load. A device selected only on average wattage can still suffer a permanent resistance shift or failure if its resistive film and electrode system cannot withstand the energy in those events.
ROHM positions SDR01 above its earlier ESR anti-surge family for surge capability while also increasing rated power in the same 0402 footprint. The existing ESR01, for comparison, is rated at 0.25W, giving designers additional continuous-power margin without immediately moving to a larger package.
That does not make a smaller component an automatic replacement for every larger resistor. Working voltage, pulse energy, overload behaviour, tolerance, derating, PCB temperature, and required reliability still have to be checked against the actual circuit. Consolidating parallel resistors also changes current distribution and board-level thermal behaviour even if the combined nominal power rating appears equivalent.
The strongest application case is therefore where PCB area is already scarce but the surrounding layout can remove the generated heat. Power-management boards, industrial controls, automotive ECUs, and AI-server electronics increasingly combine processors, power semiconductors, capacitors, magnetics, protection devices, and communications hardware within restricted board dimensions, leaving passive-component footprints under the same pressure as active devices.
AI servers are a useful example because increasing rack power does not only affect the main processor rails. Bias supplies, monitoring circuits, protection, control electronics, fan and pump systems, network hardware, and auxiliary converters all add passive components around the high-power silicon. Saving fractions of a square millimetre repeatedly across those circuits can become worthwhile provided the thermal consequences are accounted for.
ROHM has already begun mass production of SDR01 and made the devices available through its online store and distributors including DigiKey and Farnell. Immediate availability means engineers can move from datasheet comparison into board-level thermal, surge, ESD, and reliability testing without waiting for a later production release.
The SDR01 shows the less glamorous side of electronics miniaturisation: shrinking a passive component does not shrink the energy it has to tolerate. At 0.33W in an 0402 footprint, more of the thermal work moves into the PCB, making resistor selection and board design increasingly difficult to separate.
