TMP401: TMP401

Hello Tom,

2 feet may not be the problem. Please look at section 10.1.2 of the Datasheet on Layout guidelines (point 5). What is the type of cable that you are using?

Hi Amit,
I am using an IC tester to test this device. So a PCB as describe in Figure 28 and 30 may not be available. Would it be possible to force voltage or current to D+ and D- to simulate the sensing temperature.

Thanks,
Tom

Hi Tom,

We don't have prior experience with 2N2907. Would it be possible to check with a 2N3906?

When you say it is not working, what is the reported temperature?

Thanks,
Ren

Hi Ren,
I have to order some 2N3906. When I read the pointer address 0x00. the data always 0x00, and the OPEN bit also "0".

Regards,
Tom

Hi Tom,

Register 0 is for Local Temperature. Register 1 is for Remote Temperature. Could you show us your I2C transactions on an oscilloscope?

Thanks,
Ren

Sorry. I mean register 0x02. bit D2 = 0. When I read register 0x01. I also get 0x0.

Regards,
Tom

Hi Tom,

Register 2 is the Status register. It would not be unusual to receive 0x0 when reading the status register. Could you show us your I2C transactions?

Thanks,
Ren

Hi Ren,

     I have a few jpg files containing I2C waveform. How do I attach to the tread. Is there a different way I can send it to you.

Tom

Hi Tom,

You'll need to navigate to the advanced post editor. Please see
e2e.ti.com/.../148.4-5-attaching-a-file
e2e.ti.com/.../149.4-3-inserting-an-image-on-e2e

Thanks,
Ren

Hi Ren,

      Thank you for the help. Here is the jpg files info.

Yellow   SCL

Green    SDA

Purple  trigger/sync  pulse

For reading addr 0x02  Remote Temp, their they 5 files.

dummy_write1

addr1

read_addr1

data1

data2

For reading addr 0x2

dummy_write2

addr2

read_addr2

read_data2

Thanks,

Tom

Hi Tom,

Thanks for the images. The communication looks correct. I understand that you are performing the following I2C Transactions:
Write Pointer 1 (this is Remote Temperature Register)
Read 2 bytes (this is contents of Remote Temperature Register. The contents was 0x0000.)
Write Pointer 2 (This is Status Register)
Read 1 byte (This is contents of Status register. The contents was 0x00.)

It is normal for Status register to be 0x00 under normal conditions. OPEN=0 indicates that the sensor believes there is a remote junction connected.

Were you able to acquire a 2N3906 for testing? The specifications of 2N2907 look suitable, but we have no experience with this device. I will acquire one now for testing. If this device is not compatible, it could cause the temperature result to be stuck at 0x0000.

thanks,
Ren

Hi Ren,

    Thank you for verified the waveform. I am waiting for my 2N3906. Will try it again when I receive it.

Thanks,

Tom

No, I connect Emitter to D+, Base and Collector to D-. Still read 0.

Tom

Hi Tom,

Are you reading the register immediately after power-on? It will take approximately 230ms (Conversion Time * 2 Channels) after power-on to complete the first temperature measurements.

Thanks,
Ren

Yes, I start to read the register not long after power up. I had do another reading at about 240mS after power up, still read 0x00.

Tom

Hi Tom,

Could you verify the 240ms timing with oscilloscope? Are you performing other transactions?

Thanks,
Ren

No, the time correct. No other task were perform during this time. However, I do have some pcb connectors and 2 feet of wire between the device and transistor, and the wire are not twisted.

Thanks,
Tom

Hi Tom,

Have you tested with short wire?

Thanks,
Ren