HDC2022: Temperature and Humidity

Hi Sowmiya,

Welcome to the E2E Forums. 

Sowmiya R1 said:

What are the spec differences between the HDC2022 and HDC2080?

Both devices are software compatible, but the HDC2022 has a centered sensing cavity (the cavity on the HDC2080 is slightly offset). The only major difference in specification is in the temperature accuracy as shown below.

HDC2022	HDC2080

Sowmiya R1 said:

Where is the temperature sensor located on these chips.? We see a window for the RH sensor . Is the temperature sensor also located inside this window or does it sense temperature thru the pins from the PCB.? We want to use this for sensing ambient temperature and humidity.

The temperature sensor of the HDC devices is part of the silicon die inside the package, similar to all of our IC temperature sensors. The leads and thermal pad would be the most direct path from the package to the die. For ambient measurement you can use certain layout techniques such as board cutouts (see HDC2010METER-EVM for an example) to isolate your device from the other heat sources. You can see Design Considerations for Measuring Ambient Air Temperature (snoa966) for more details on ambient temperature sensing layout. 

Sowmiya R1 said:

Do you have an IC that is similar to TMP108 but with humidity sensor integrated as well? Basically we need a T&H sensor with with a dynamically-programmable limit window, and under- and overtemperature alert functions.

All of our HDC2x family devices will have these limits that function similarly to TMP108. Including dynamically programmable limits.

Sowmiya R1 said:

• We want to use the HDC2022 in continuous acquisition mode with interrupts generated when the temperature exceeds the high limit or temperature falls below the low limit. Based on the HDC2022 data sheet , we would have to set register 0x07 to 0xE0 and wait for the interrupt to be generated to wake up our processor.  So we should be able to get an interrupt under either of the two condition right?  that is either the temp goes below the temp_thr_L or temp goes above the temp_thr_H. Please confirm.
• But your data sheet note on page 12 ( screen shot attached below ) says,  the interrupt for low temperature will be generated only if we disable the interrupt for the high temperature. .?  We are not clear on what this means.  This seems to contradict our assumption #3 above.  Can you please clarify. 

I believe your understanding of the interrupt scheme based on that note from the datasheet is correct. Enabling the DRDY/INT pin to track one interrupt should mask the others based on those priorities.  

Checking on our HDC2022EVM though, I was able to get interrupts from both high temperature and low temperature when both were enabled. I am checking with our design team on this behavior and I will get back to you on this shortly. 

Best Regards,
Brandon Fisher

Hi Brandon,,
  Thanks for your reply.I have attached our layout design pictures of HDC2022 .Please check and let us know whether  the design satisfies all the guidelinesHDC2022 Layout Document.pdfs.

Hi Brandon,

Is there any update after checking HDC2022EVM get interrupts from both high temperature and low temperature?

Thanks,
Sowmiya

Hi Brandon,

Thanks much for  your valuable reply.It helped us .We will reach you further in case of any queries.Also if you have any updates regarding the alert,please let us know.

Thanks,
Sowmiya

Hi Brandon,
      Thanks much for all your valuable replies.We would like to know,if there is any curing time/procedure for the sensor,after the sensor is placed in PCB board.

Thanks,
Sowmiya

Hi Sowmiya,

Yes. After assembly it will take some time (up to several days) for the sensor to recover and return normal readings after reflow conditions. Section 10.1.1.2 of the HDC2022 datasheet briefly describes this.

Best Regards,
Brandon Fisher

HI Brandon,
   Thanks again ,for your immediate and valuable response.

We would like to know,whether is there any fixed curing time before we power up the sensor.As this is important for us to qualify the behavior after SMT.So please let us know.

Thanks,
Sowmiya

Hi Sowmiya,

To clarify, you can power up the sensor at any point after reflow is completed without risk of damaging it. The note I shared from the datasheet actually just refers to an observed RH offset (typically negative) in the HDC2022 immediately after assembly. You will observe this if you try to take any RH measurements after assembly.

The exact amount of time for the sensor to recover RH accuracy will vary based on ambient conditions, but I have seen it take up to 4 days. 

Best Regards,
Brandon Fisher

Hi Brandon,

 Here are our few questions after working on HDC2022

1. The Temp/Humidity data registers are 16 bit.  If we set the resolution as 14 bits,  should we take 14 bits from MSB or from LSB ?

2. Pls see continuous mode I2C reads from the Temp register.  Our NIST certified thermometer shows 26 Deg C on the PCB at the HDC chip area/pins , but the HDC chip is reading a good 5-6 Deg C higher. Wondering if we are setting something wrong with the registers.? Please clarify. I have Attached Logs and screen shot of received temperature.

3/ Also we see that the temperature is jumping by 1-2 Deg C between consecutive readings even though the board and ambient temperature is maintained constant.?

For #2, 3 we power up the chip immediately  within hours after soldering it down. Could this be a reason for the temp shift.? ( we thought only Humidity will have a shift in such a case )

Thanks,
Sowmiya 

Hi Sowmiya,

The two LSBs of the humidity and temperature register are what should be ignored. You can mask them off if you want, but if left, they only end up contributing meaningless noise to the measurement result.

Sowmiya R1 said:

2. Pls see continuous mode I2C reads from the Temp register. Our NIST certified thermometer shows 26 Deg C on the PCB at the HDC chip area/pins , but the HDC chip is reading a good 5-6 Deg C higher. Wondering if we are setting something wrong with the registers.? Please clarify. I have Attached Logs and screen shot of received temperature.

3/ Also we see that the temperature is jumping by 1-2 Deg C between consecutive readings even though the board and ambient temperature is maintained constant.?

What is your testing setup like? Do you have the devices inside a chamber or stirred liquid bath, and how far away is the sensor from your calibrated thermometer? 

If your environment is unstable you will see some oscillation between device readings, but 1-2C is significant, and 5-6C of absolute error is also very large. Is just the HDC2022 on, or are there other devices (specifically high powered devices) on the board being powered?

Sowmiya R1 said:

For #2, 3 we power up the chip immediately within hours after soldering it down. Could this be a reason for the temp shift.? ( we thought only Humidity will have a shift in such a case )

If your boards are still hotter than ambient due to reflow that will affect the temperature results. I would typically expect a few hours to be enough for the board to cool down completely, but this is affected by a few variables such as board size and ambient conditions. You could measure the board temperature with an external reference a few hours after reflow to try and determine if this is really the cause. 

Best Regards,
Brandon Fisher

Hi Brandon,

We have few queries related to setting,please help us with the below query,
We are testing temperature sensor HDC2022 with our controller and we can able to make settings then read back temperature's from temperature high(0x01) and temperature low(0x00) registers. Now we are trying set DRDY/INT_EN for high and low temperature alerts, but the pin doesn't vary in voltage level when the temperature crosses high or low programmed level.We can see the status registers (0x04) values changing as below, 0xa0 for below low temperature
0xc0 for above high temperature
0xe0 for inbetween high and low temperature level.Below are our settings for temperature measurement, Device configuration register (0x0e) - 0x54 High temperature limit (0x0a) - 0x75 for 35.7058C Low temperature limit (0x0b) - 0x66 for 26C Interrupt Enable register (0x07) - 0x60
Measurement configuration (0x0f) - 0x01Please guide us to make the DRDY/INT_EN pin go high or low when the temperature crosses high or low set limit.

Thanks,
Sowmiya

Hi Brandon,

   Thanks much for your valuable feedbaack.I would like to know,whether HDC2022 is in production .If its in production,we need 1000 or 2000 nos everymonth starting from December.SO please confirm the production status.

Thanks,
Sowmiya

Thanks Brandon for your reply.

In all distributor's site and in TI site,we could see the stock only around 2K .But we would like to buy  5K qty.So i need to know whether the HDC2022 sensor's production is active .

Thanks,
Sowmiya

Hi Brandon,

     Thanks for your guiding us so far.Now when we go for controlled environment check in chamber, For temperatures 40 ,50 and 60 deg ,the actual temperature read from register is minimum.(For example, the device temp is 38 when chamber is set to 40 and corresponding reference  temp meter shows  40.4 deg  ).Can you please guide us on this?

Thanks,
Sowmiya

Dear Sowmiya - 

is the data being collected continuously and compared, or just observed and recorded? a difference this large between DUT and reference meter would indicate either a large gradient exists in the chamber between the units or there is something inhibiting heat conduction to the part under test. Do you have any images of the test setup?   

Sowmiya - 

i can only imagine here there would be some error from when/how the data is taken - sometimes a chamber will jump around a bit and if one is manually taking data by looking at three different sources at about the same time, errors can occur - if you can share brief datalog and images of your setup and board that the HDC2022 is mounted on, that would be a helpful start towards a suggestion.