LM75A Temperature Control Module | U2 Position Repair for Antminer S19 / S19kpro / S21 / T21 Hashboards
The LM75A is the digital temperature sensor IC sitting at the U2 position on Antminer S19, S19kpro, S21, and T21 hashboards. It monitors hashboard temperature and feeds the controller's thermal-protection loop — when the LM75A fails, the controller either reads a stuck temperature (preventing thermal throttling) or trips a false over-temperature shutdown.
Operating temperature range -55°C to +125°C. The sensor reports temperature to the miner controller over the I2C bus, allowing software-readable temperature monitoring for fan-speed control and thermal-protection logic.
When to Replace the LM75A
Hashboard reports stuck temperature — always reads the same value regardless of load.
Phantom over-temperature shutdowns — controller trips thermal protection when board is actually cool.
Temperature reading missing from miner log — sensor not responding on I2C bus.
Visible damage on the U2 position chip — burnt or cracked package.
LM75A Specifications
Feature
Specification
Module Type
Digital Temperature Sensor
Temperature Range
-55°C to +125°C
Interface
I2C bus
Compatible Hashboard
Antminer S19 / S19kpro / S21 / T21 (U2 position)
Function
Temperature monitoring + thermal-protection input
Installation
SMD replacement at the U2 chip location
FAQ — LM75A Temperature Sensor
Q: How do I confirm the LM75A is the failed part? A: Read the miner log — if temperature is reported as 0°C, 127°C, or a stuck value, the sensor is failed. Probe the I2C bus (SCL / SDA pins) with a scope: healthy sensor responds to address polls; failed sensor produces no acknowledgment.
Q: Are there multiple LM75A positions on the hashboard? A: Most Antminer hashboards have several temperature sensors at different positions. The "U2" designation refers to one specific location. If multiple sensors fail, replace each — controllers typically average or use the highest reading for thermal-protection logic.
Antminer S19 / S21 / T21 hashboard repair benches stocking LM75A sensors in volume? Email contact@lys-sz.com for tape-and-reel pricing. Worldwide shipping from our Shenzhen warehouse.
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