MC9S08LC60-based board: Sinks too much current as soon as I connect the battery...

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MC9S08LC60-based board: Sinks too much current as soon as I connect the battery...

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onder_arik
Contributor I
Hi,
 
We designed a MC9S08LC60-based board and we have just received the PCBs.
 
1. On the PCB, we have just placed the MC9S08LC60 microcontroller, the BDM connector and battery connector. Nothing else.
2.  We have checked all the short circuits, especially around the MC9S08LC60 (IO pins etc.) , none detected.
3. We are using USB Multilink Interface from the PEMicro as BDM debugger. It is tested on other demo boards.
4. We have connected the USB Multilink to the board. Battery not connected yet.
5. Then we have connected the battery, the BDM works okay, we start programming the flash for the first time.
6. Then a few seconds later, the programming interrupted due to power loss.
7. When we have checked, we have seen that the MC9S08LC60 sinking too much current somehow. (around 100mA).
8. In the next trial, we did not connect the BDM. Just connected the battery. Still consumes too much current.
9. Note that, all LCD related pins are floating since we do not use any LCD. In fact, all IO pins are floating, there is no other components on the board yet.
 
We need your urgent help at this point
 
   
 
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jtjans
Contributor I
    onder.arik

I think your power problem stems from the fact that the 9S08 processor ports default to inputs with no pullups.  w/hen they float they draw a fair amount of current internally.  When power is applied. any floating port must be made an output or given a pullup.  This includes those not bonded out.  You are also powering the multilink.

jtjans
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onder_arik
Contributor I
Some extra explanation:
 
You can think of all pins of the MC9S08LC60 is floating except:
 
VREFH: Connected to 3.3V
VREFL: GND
VSSAD: GND
VSS: GND
VDD: 3.3V
PIN31: Directly connected to PIN39
PIN39: Directly connected to PIN31
 
 
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