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How to design voltage detector without bandgap reference?

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jordan76

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voltage detectors design

Gurus,

I need to design a voltage dectector circuit and the supply voltage range is 1.6v~6.0v.But I have no bandgap reference voltage as my reference,
can anyone give a hint or some reference sources?

One more thing to add:
suppose the voltage range is roughly divided into three parts:
1.6v~2.5v,2.5v~3.8v,3.8v~6.0v by two threshold,
the detector threshold offset is within 200mv.

Thanks a lot!
 

Re: How to design voltage detector without bandgap reference

You can refer to Razavi's book.He bring up a circuit structure before the bandgap circuit.
 

Re: How to design voltage detector without bandgap reference

If temperature doesn't change too much, you could use a diode polarized at a (nearly) constant current as a reference.
 

Re: How to design voltage detector without bandgap reference

Hi Jordan76,

I found with LEDs that they have a much better voltage/current characteristics than for instance Zener diodes, even at a few mA forward current when they just start to light.
So they can be used as a low voltage current regulator very nicely.
A red LED has a forward voltage at around 1.5V and a white LED has around 4.2V. By connecting any two of them in series, you can get different stable voltages, by selecting green, or yellow or red etc. LEDs in a pair OR using only just one of them.
Just like with a normal Zener they need a resistor of some hundred Ohms or around 1 kOhm or so and 2-3mA forward current, not more and they keep their forward voltage much better than Zeners.

regards
unkarc
 

if you have some input signal whatever it is, it can be used, e.g. the data input from another chip can be used as the reference with it's peak value
 

of couse, if your requirement is not too tough,diode can be used
 

Re: How to design voltage detector without bandgap reference

First of all, many thanks to all!

Maybe I should make it more clear as follows:
What I need to design is a voltage detector circuit for power supply Vdd ranging from 1.6V~6V and temperature ranging from -40C to 125C.

The circuit has one input: power supply Vdd,
and three logic outputs: Low, Mid, High which indicate whether Vdd is in
1.6V~2.5V,2.5V~3.8V,3.8V~6V or not.

joskin,
I will take a look at Razavi's book later.

Humungus,
Unfortunately the application is for automotive product, so the temperature range is very vast.

unkarc,
I am afraid LED is not available in generic CMOS process. Your idea is a good catch for me, however.

adanshen,
Actually the requirement is quite tight, accuracy should be within 200mv.

regards,
jordan76
 

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