Three state indicator

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

Looks good to me.

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.

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.

ericgibbs said:

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

Click to expand...

Well, that is either, great minds think alike, or, fools never differ.

Mike.

ericgibbs said:

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.

Click to expand...

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

Pommie said:

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.

Click to expand...

Thank you Mike,

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

Regards

Hans

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

Ken