The MAX6657/MAX6658/MAX6659 are precise, twochannel digital temperature sensors. Each accurately measures the temperature of its own die and one remote PN junction, and reports the temperature in digital form on a 2-wire serial interface. The remote junction can be a diode-connected transistor like the low-cost NPN type 2N3904 or 2N3906 PNP type. The remote junction can also be a common-collector PNP, such as a substrate PNP of a microprocessor. The 2-wire serial interface accepts standard System Management Bus (SMBus) commands such as Write Byte, Read Byte, Send Byte, and Receive Byte to read the temperature data and program the alarm thresholds and conversion rate. The MAX6657/MAX6658/MAX6659 can function autonomously with a programmable conversion rate, which allows the control of supply current and temperature update rate to match system needs. For conversion rates of 4Hz or less, the temperature is represented in extended mode as 10 bits + sign with a resolution of 0.125C. When the conversion rate is faster than 4Hz, output data is 7 bits + sign with a resolution of 1C. The MAX6657/MAX6658/MAX6659 also include an SMBus timeout feature to enhance system reliability. Remote accuracy is +-1C between +60C and +100C with no calibration needed. The MAX6657 measures temperatures from 0C to +125C and the MAX6658/MAX6659 from -55C to +125C. The MAX6659 has the added benefit of being able to select one of three addresses through an address pin, and a second overtemperature alarm pin for greater system reliability.