Problems booting the board

Hi hope on some help - quickly.

We have made our own board for our product using the Classic Q2687 GSM engine, but the bootong is not happening.

I have tried to go through the documentation again and again but have not found the answer :frowning:

The problem is that the board is not starting after applied power supply; the On/Off pin is tiered high, boot and reset pins are floating.

What have i forgot?

The 1.8Vdc present on the B2B connector pin 5; here i measure VBATT? (3.6Vdc)
the Reset pin on B2B connector pin 18 is floating (internal pull up according to the documentatio) on this pin i beasure 0.250Vdc

Best regards



Sounds like your modem has died. 4V2 on the 1V8 rail is a good sign that the internal regulators are no longer running. :frowning:

How much current are you pulling from the 1V8 and 2V8 pins? Remember that there is 15mA MAXIMUM available from each of these outputs. Remember also that some of the I/O is spec’d for 2V8 levels, and some for 1V8 levels. You can’t mix and match - or you’ll let the smoke out.

Try these steps:

  • Take the modem off the board.
  • Carefully examine the system connector to make sure that there are no pin to pin solder bridges
  • Power up your board (without the modem)
  • Test each connector pin (with an ocilloscope) to make sure that it is not exceeding the documentation specifications

Once you are sure that all I/O is within spec, try a new modem.

As an aside, isn’t the Q2687 Classic (going) obsolete? Shouldn’t you be designing around a current part?

ciao, Dave


Thanks Dave for your quick reply

The board is not dead, we have an SDK and whent mounted there it is working (?)

The maximum current out of the 1.8V pint is as you wrote limited, but we are not using it, i just measured it and got confused.


Power supply issues?

See: viewtopic.php?f=7&t=3766&hilit=wiki#p16724

Just a doubt, when powering module, ON/OFF pin must be set low (then tied high) or can goes high directly when powering the modem?

Hi All

I found a serious problem - we unfortunately have a error in our PCB so no matter what we have to make another PCB.
THX for your kind replys.