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Three state indicator

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Boncuk

New Member
Hi,

I'm about building an Li-Ion charge circuit for my camera since the orignal one is lost.

The charger IC is the BQ24200 (TI) with a tri-state status output pin.

When the battery is being charged that pin has high state (VDD-1.5V), when charging terminates it goes low (0.5V) and on any fault condition it goes to high-z state.

I intend to indicate all three states using LEDs.

Attached is a schematic (high, low and high-z) with all three LEDs lit according to the status output of the chip.

Is there any more elegant way than using a window comparator for this?

Boncuk
 

Attachments

  • HIGH.gif
    HIGH.gif
    12.9 KB · Views: 168
  • LOW.gif
    LOW.gif
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  • HIGH-Z.gif
    HIGH-Z.gif
    12.9 KB · Views: 124

Pommie

Well-Known Member
Most Helpful Member
A resistor + LED to gnd will indicate charging, same to Vdd will indicate charged. A PNP + NPN biased at 1/2 Vdd with an LED between collectors will indicate floating. See attached.

Mike.
 

Attachments

  • float.png
    float.png
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ericgibbs

Well-Known Member
Most Helpful Member
hi Hans,
Ref your PM of last week, didnt you like my suggested circuit.?

I see that Mike has posted virtually the same elegant solution.:rolleyes:
 
Last edited:

Boncuk

New Member
hi Hans,
Ref your PM of last week, didnt you like my suggested circuit.?

I see that Mike has posted virtually the same elegant solution.:rolleyes:

Hi Eric,

nothing to be worried about. I did exactly what you suggested: Have the output pulled on 1/2VDD and use a window comparator. It works fine in the simulation, but a few chips too much.

Regards

Hans
 

Boncuk

New Member
A resistor + LED to gnd will indicate charging, same to Vdd will indicate charged. A PNP + NPN biased at 1/2 Vdd with an LED between collectors will indicate floating. See attached.

Mike.

Thank you Mike,

I'll simulate it first and then ripup my schematic and PCB design. :)

Regards

Hans
 

KMoffett

Well-Known Member
Seems like the perfect use for one 8-pin PIC.

Ken
 
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