HDC2010/HDC2080 Temperature and Humidity Sensing - Register Corruption Issue

Abnormal temperature and humidity readings were observed due to register corruption in HDC2010/HDC2080 sensors. The root cause was traced to a floating node in the level shifter circuit, which affected signal levels. Verified workarounds involve limiting VDD, entering and exitting Custom Mode, and software resets to address the issue effectively.

• Temperature and Humidity Sensing
• Register Corruption
• HDC2010
• HDC2080
• Root Cause

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1. HDC2010/HDC2080 Register Corruption Texas Instruments Temperature and Humidity Sensing 04/2021 TI Confidential Selective Disclosure 1

2. Table of Contents Summary Observed Device Behavior Root Cause Explanation (verified) Verified workarounds (verified on validation and application setups) TI Confidential Selective Disclosure 2

3. Issue observed While measuring temperature and humidity from registers (0x00 through 0x03), it was observed that an abnormal value of high temp and low % RH, as well as normal temperature and high %RH values. Upon reading the registers after power up, it was seen that register 0x0F was a non-default value. Value was 0xF6, should have been 0x00. 0xF6 is listed as NA configuration and prohibits the part from working correctly, as observed. 11110110b = 0xF6 = Not Applicable configuration TI Confidential Selective Disclosure 3

4. Root Cause Explanation (Verified) Floating node in Level Shifter 1.5V level signal VDD level signal Various Control Signals HDC20xx Register Map The HDC20xx register map operates at VDD, however there are signals routed to the register map from the internally regulated lower voltage domain of the device, and these signals each need a level shifter when VDD is higher than 2.3VDC. Inside the level shifting circuit (that is only used when needed) a common floating node was discovered in the schematic. NOTE: Floating node means there are signals which are not driven to a predefined logic 1 or 0 directly on power up (as they should be and normally are). This is root cause of issue seen as observed register corruption upon power up and subsequent behavior of the device (as described on the previous slide) If this is seen on a unit, there is a verified firmware workaround available that can be strategically be placed at initialization after POR time or as case statement upon detection. If the design is using or can use input voltage to the HDC20xx lower than 2.3VDC (i.e. 1.8VDC) this issue will never be seen. TI Confidential Selective Disclosure 4

5. Verified Workarounds Solution # Description Tradeoffs 1 Limit VDD to 2.30V maximum - Additional LDO if system power rail is not available 2 Enable Custom Mode, then Exit, then re-enter Custom Mode (see programming sequence below) Initiate software workaround as soon as possible after VDD has reached steady state. Wait at least 10 seconds before initiate a sensor measurement. - 200 A sleep mode IDD 1, 7 Command # Register Address R/W Data Definition 1 0xF1 W - Custom Mode Entry 2, 8 2 0xE7 W - Custom Mode Entry 3 0xFF W - Custom Mode Entry 3, 9 4 0x45 W 0x04 Turns on LDO 5 0xE1 W - Exit Custom Mode 4, 10 6 0x0E W 0x80 Software Reset 7 0xF1 W - Custom Mode Entry 8 0xE7 W - Custom Mode Entry 5, 11 9 0xFF W - Custom Mode Entry 10 0x45 W 0x04 Turns on LDO 6 11 0xE1 W - Exit Custom Mode TI Confidential Selective Disclosure 5

6. BACKUP TI Confidential Selective Disclosure 6

7. Register map issues (Typical registers corrupted) Device Behavior: At VDD > 2.3V, configuration of user registers can be observed as modified from default after power up and after issuance of soft reset (0x07 to register 0x0F) Observed in both Auto Measurement Mode as well as One Shot mode. Problem is made worse at higher Temperatures and higher supplies. TI Confidential Selective Disclosure 7