SNAS207B May 2004 – January 2024 LM64
PRODUCTION DATA
The LM64 can detect fault conditions caused by the remote diode. If the D+ pin is detected to be shorted to VDD, or open: (1) the Remote Temperature High Byte (RTHB) register is loaded with 127°C, (2) the Remote Temperature Low Byte (RTLB) register is loaded with 0, and (3) the OPEN bit (D2) in the status register is set. Therefore, if the Remote T_CRIT setpoint register (RCS): (1) is set to a value less than +127°C and (2) the ALERT Mask is disabled, then the ALERT output pin will be pulled low. If the Remote High Setpoint High Byte (RHSHB) is set to a value less than +127°C and (2) the ALERT Mask is disabled, then the ALERT and T_Crit outputs will be pulled low. The OPEN bit by itself will not trigger an ALERT.
If the D+ pin is shorted to either ground or D−, then the Remote Temperature High Byte (RTHB) register is loaded with −128°C (1000 0000) and the OPEN bit in the ALERT Status Register will not be set. A temperature reading of −128°C indicates that D+ is shorted to either ground or D-. If the value in the Remote Low Setpoint High Byte (RLSHB) Register is more than −128°C and the ALERT Mask is Disabled, ALERT will be pulled low.