The LM95221 is a digital temperature sensor produced by Texas Instruments. It uses the SMBus 2.0 interface and can detect three temperature zones, including its own temperature and the temperature of two diode connected transistors. The diode connected transistors can be a thermal diode as found in Pentium and AMD processors, or simply be a diode connected MMBT3904 transistor. The LM95221 remote temperature reading resolution format can be programmed to be 10-bits plus sign or 11-bits unsigned. In the unsigned mode, the LM95221 remote diode readings can resolve temperatures above 127 degrees Celsius. Local temperature readings have a resolution of 9-bits plus sign. Any ASIC can be accurately determined using the LM95221 as long as a dedicated diode (semiconductor junction) is available on the target die. The LM95221 remote sensor accuracy of ±1 degrees Celsius is factory trimmed for a series resistance of 2.7 ohms and a 1.008 non-ideality factor.
The LM95221 is a dual remote‑diode temperature sensor packaged in an 8‑lead MSOP. It can measure its own die temperature and two external diode‑connected transistors via a 2‑wire SMBus‑compatible serial interface. The device provides programmable resolution (10‑bit plus sign or 11‑bit unsigned) and supports shutdown and one‑shot conversion modes for power saving.
Key features include 0.125 °C LSB for remote readings, 0.25 °C LSB for local readings, fault detection for remote diodes, and a configurable conversion rate. The datasheet details pin functions, electrical characteristics, SMBus timing, and layout recommendations to minimize noise and ensure accurate temperature measurement.
| Local Temperature Resolution | 0.25 °C per LSB |
|---|---|
| Remote Temperature Resolution | 0.125 °C per LSB |
| Local Temperature Accuracy | +3.0 °C (max) @ 0 °C‑85 °C |
| Supply Current | 2 mA (typ) |
| SMBus Clock Frequency | 100 kHz (max) |
| Conversion Time | 66 ms |
| Shutdown Mode Current | 335 pA |
It can sense three zones: its own die temperature and two remote diode‑connected transistors.
Remote temperature readings have a 0.125 °C LSB, with either 10‑bit plus sign or 11‑bit unsigned resolution.
The device provides a shutdown mode and a one‑shot conversion control to minimize power consumption when temperature data is not needed.