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ADS1230 interfacing 8052 Microcontroller

ajith kumar
Intellectual 320 points
Other Parts Discussed in Thread: ADS1230

Dear Bob,

   I introduced new PCB(double sided) for interfacing ADS1230 and 8052 microcontroller for weighing purpose.I used the hand soldering method to solder the sample PCB,s.I also checked for short circuit between the IC pins.Seems everything Ok .But after switch ON the ADC board the count is drifting.The counts are increasing and decreasing rapidly upto 100 counts continuously.I provided enough filtering to reduce noise..But the problem is not solved yet.I m unable to recognize what,s the exact problem in the hardware section...My doubts are...

1)Which types of soldering are recommended for ADC IC's.

1)Is hand soldering are safe for ADC IC.

2)Which type of flux are recommended for ADC IC soldering..(what cause if use ordinary flux)

3)How much temperature can an ADC IC withstand,during soldering.

4)Is there any problem if flux are still present in between the IC pins after soldering.

5)In my PCB the tracks to drive 7 segment displays are passing near to the track of ADC IC,s pin no:7 and 8(load cell input) ,Is there any chance of noise generation from there.

6)The 5 volt supply is connected to ADC IC first,then it passes to Microcontroller,then to EEPROM and finally it passes to Display Driving transistors.(Is my connection correct ,to reduce noise).

Please Help Me...

                            Thanks In advance

                                     By Ajit..

  • 0
    TI__Guru** 113765 points

    Ajit,

    I don't recall if you have previously provided your schematic/gerbers for review.  When you  have instability in your system, it can be caused by a number of different or even a combination of issues.  Generally speaking, if you have a surface mount component it is designed for a reflow soldering environment.  However, you can safely hand solder surface mount components.  See this post regarding temperature and soldering conditions.  It also applies to your device.

    http://e2e.ti.com/support/interface/industrial_interface/f/142/t/137620.aspx

    Any flux can be used as long as it adequately cleans the surface upon activation.  The biggest problem with flux is making sure that the board is adequately cleaned.  Also the removal process will depend on the type of flux used.  No clean flux should be cleaned as well when hand soldering.  This is because the flux is seldom completely activated leaving conductive residues.  Some fluxes are conductive, while others are at the very least a dielectric and can capacitive couple pins.  So cleaning is very important.

    Digital signals should not be routed in analog areas....especially sensitive analog.  Remember that the analog inputs are gained up to at least a gain of 64 (or 128).  Also, good ground planes are essential for providing good return paths.  The supply should be adequately bypassed, to include low inductance grounding at the capacitor.  You will see a large varying of counts if your excitation voltage or reference voltage is noisy.  Ratiometric measurements (where excitation supply and reference supply is the same) help with drift/noise as what is common will cancel in the measurement.

    You should be able to meet the datasheet numbers if you have properly designed and PCB layout is optimum.  The datasheet noise numbers measured with shorted inputs and biased at mid-supply of AVDD (in other words shorted together at 2.5V.)  This is the best case scenario.  If you are not able to match the noise numbers at this configuration, you will not achieve a high performance operation.

    Best regards,

    Bob B