MPL115A1 returns "0" for Pressure and Temperature, not coefficients.

[zzzzz]

Dear all.

MPL115A1 always returns "0" when I read the pressure and temperature. I can read and verify all coefficient bytes.

One strange problem is that the voltage at the internal regulator (pin2) is 0 as well, even with a 1uF cap.  No wiring problem since the schematic is so simply. This could be related problem.

I cannot  figure out what the problem is. Help is appreciated.

Thank you.

Zzz

[Joshevelle]

Hello Zzz,

Did you hand soldered the MPL115A?  It is very sensitive to temperature while soldering, please take a look at the following soldering profile, we wouldn't recommend hand soldering for these devices.

1. Use SAC solder alloy (i.e., Sn-Ag-Cu) with a melting point of about 217°C. It is recommended to use SAC305 (i.e., Sn-3.0 wt.% Ag-0.5 wt.% Cu).
2. Reflow:

• Ramp up rate: 2 to 3°C/s.

• Preheat flat (soak): 110 to 130s.

• Reflow peak temperature: 250°C to 260°C (depends on exact SAC alloy composition).

• Time above 217°C: 40 to 90s (depends on board type, thermal mass of the board/quantities in the reflow).

• Ramp down: 5 to 6°C/s.

• Using an inert reflow environment (with O2 level about 5 to 15 ppm).

I do suggest looking at a newer part - MPL3115A2. It has a calibrated temperature output in degrees Celsius as feedback was taken from our customers who use the MPL115A and input into that design. The MPL3115A2 allows direct pressure and altitude reading (no additional computing needed). It also includes embedded functions and user-programmable options, such as temperature compensation. Smart features include autonomous data acquisition with two interruptions on thresholds detection. For more information about this part, please click in the following URL:

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MPL3115A2

[stevenbremner]

Hi There,

Is the soldering profile you show above applicable to the newer MPL3115A2 device as well?

Also, are there any guidelines/restrictions on washing PCB's (as part of the assembly process)

which have had the MPL3115A2 device fitted?

Thanks for any info on these points.

Kind Regards,

Steven.

[Joshevelle]

Hello Steven,

Yes, you can use the same soldering profile.

Regarding washing PCBs, we highly recommend our customers to block the pressure port of the sensor with Kapton tape. The pressure port of the MPL3115A is the small pink hole in the top of the package.

-Josh

[stevenbremner]

Hi Josh,

Great stuff - thanks for the quick reply.

Regards,

Steven.