controller Charge Pump?

[toalan]

Hey guys I am looking for something that can act as a charge pump. Bascially I need an IC/Design that can pump out a definite quanta of charge each time it is activated. Activation would come from a voltage source.


The maxium continous rating would be less than 10 mA. Hopefully you guys know an IC that can be of use.

[Ron Marcus]

I need more info. Why a charge pump? What is your initial voltage? What is your needed voltage? I have run a 5 volt LCD screen from a 3 volt PIC using the PWM output. There are app notes for pushing out over 200 volts using a step up coil and diodes from a lowly PIC!

I like coils for step up, but the EMI can be a problem. What is the application?

Ron

[toalan]

the application is a bit odd. it is to control an oxygen sensor is a car, basically i need to source enough charge such that the catylitic reaction in the oxygen sensor is at steady state.

The amount of charge i need to pump in to reach that steady state is proportional to the amount of oxygen left over from internal combustion. it is this amount of oxygen that i am intersted in measureing. Most designs use voltage source pushing current through a small resistor to supply the current needed, and then use A/D to find to voltage drop across the resistor to find the steady state current.

But I would like to do away with using A/Ds, if i had a way to use PWM to control a charge pump or current source that would make things alot simplier.

I need something that I can control percisely to do the following:

supply: -4ma to +4ma
the voltage range of operation would be between -5V to 5V.

I am a bit stuck in finding something, I can explain things in more detail if needed but basically I need a PWM controlled current source/charge pump, even a voltage controlled current source/chrage pump is okay, My only requirement is that the resolution and percision need to be high and it should not be very complex.

Regards

Alan To

[Luciano]

What about using a standard zirconium lambda sensor?

Sensor output ranges from 0.2 Volts (lean) to 0.8 Volts (rich).
A perfectly balanced or "stoichiometric" fuel mixture of 14.7 parts
of air to 1 part of fuel gives an average reading of around 0.45 Volts.

Luciano

[toalan]

I am wokring with a wideband sensor and not the narrow band sensors.

[Luciano]

See this link:
http://wbo2.com/2a0/schem.htm

[eoasap]

I need more info. Why a charge pump? What is your initial voltage? What is your needed voltage? I have run a 5 volt LCD screen from a 3 volt PIC using the PWM output. There are app notes for pushing out over 200 volts using a step up coil and diodes from a lowly PIC!

I like coils for step up, but the EMI can be a problem. What is the application?

Ron

Ron, how do you run a 5V LCD from a 3V PIC using PWM ? i'd love to try it out.

[Luciano]

April 02, 2007

Hi,

I have completely abandoned this project.
Please do not send me private messages about this thread.

Best regards,

Luciano

[rwskinner]

So basically, if I understand this entire deal...

The Bosch chip outputs a voltage called Vcj and this voltage allows you to calculate IP.

IP = (Vcj -1.5) / 1.053 This works fine!

Now that you know the IP, you must do a lookup using the values that Bosch provided in the lookup table for IP vrs. 02%

Cool, now how in the world do you make their Math work on Xo2 to Lambda?

They have a formula stating...

Lambda = (Xo2 / 3 + 1) / ( 1 - 4.76 * X02)

Then they show the following as references....

IP = 1.40 = 12.0% Xo2 = 2.42 Lambda

IP of 1.40 = 12.0% Xo2 (This works fine)
IP of 1.40 = 2.42 Lambda <- Does not work

This does not work given the above formula using 12.0% Xo2 or I'm doing Math Wrong.

Lambda = (Xo2 / 3 + 1) / ( 1 - 4.76 * X02)

X02 = 12.0
12.0 / 3 = 4 + 1 = 5
12.0 * 4.76 = 57.12
5 / (1 - 57.12) = 5 / -56.12 = -0.089

Where am I going wrong?