controller Charge Pump?

[Luciano]

Hi,

Print the page 3 and 4 of the CJ120 PDF.
(The Block diagram page and the Application circuit page).

http://www.semiconductors.bosch.de/p...y_extended.pdf

Add to the application circuit the two op-amp's and connect them
as they are depicted on the block diagram page.
(Draw that with a pencil inside the CJ120 on page 4).


The two op-amp's:
Pumpstrom-Regler = Pump current control
Pumpstrom-Meßverstärker = Pump current sense amplifier


Voltages:

==============================================
PIN Vcc = +5 V
==============================================
PIN VM = +2.5 V (Virtual ground voltage source)
(0.5 x VCC)
==============================================
PIN US = +2.95 V (Nernst cell reference voltage source)
(450mV, reference to virtual ground)
===============================================
PIN GND = 0 V
================================================

The two op-amp's have a single polarity supply.
(+5 and GND).

On the output of the op-amp "Pump current control"
you will need a 100 ohm resistor.


* * *

The idea is to replicate what Bosch is doing inside the CJ120.

You will need a way to simulate the LSU4 during the testing of the circuit.
(DC +/- milliampere meter and a voltage that goes from 4.0V down to 2.5).

Do you understand how it works?

Luciano

[toalan]

I have not seen the additions you have made on the PDF because the current computer I use gives an error with the file, I will look at it later on a nother computer.

I pretty much understand how the circuits works. I have made a citcuit long time ago that was very similar to what the Bosch ICs are doing. That was with analog circuits right now I am trying to do most of the Analog stuff using a MCU so to minimize tolerance problems and to cheapen things up and also to add dataloggin capabilities to it.

I built my first circuits based on the Bosch Datasheet for the Sensor itself because I never knew the Datasheets for the ICs existed publicly. The circuit I built before knowledge of the Cj120 datsheet was similar in many ways to the CJ120 but more simplier. Now that I seen the CJ120 the only thing I can not understand is on Page 3 or 4 of the CJ120 PDF, the use of Rical (82 ohms). The fact that I can not speak German only adds to the problem. But I am sure somewhere in my subconcious my mind is solving the issue, so it will only be a matter of time before I know what the RiCal does. I suspect it maybe a reference restance that the resistor in the pump Cell (Ri) should be at during normal operations. The reason I say this is becasue I know pretty sure that the Pump resistance should be close to 80 ohms during normal operation and not the 100 ohms that is shown on the diagram.

There is no need to simulate the BOSCH LSU sensor in my testing since I have about 4 of them lying around. Also the Pump current goes through an external 61.9 resistor, I suspect the 100 ohms you are talking bout is the internal resistance of the pump cell.


I would love to by the bosch ICs from rutronik but they require huge quantity purchases something in the thousands per order.

If I can digitize most of the analog circutry I can make a very cheap, fast and accurate Wideband reader.

[toalan]

BTW Luciano TY very very much for posting up the documents, because of the new information I found in there I am going to make a few design adjustments to my circuits and MCU program.

[Luciano]

================================================== ======
My previous post:

The PDF was not modified. You will have to draw the two op-amp's
and their connections on page 4. The 100 ohm resistor on the output
of the op-amp "Pump current control" is present in the Tech Edge circuit.
================================================== ======


The CJ120 also measures the Nernst-cell internal resistance (Ri) which
is used to determine the temperature of the sensor. The internal resistance
of the Nernst-cell is 80 ohm when the sensor ceramic temperature is approx. 750°C.
By knowing the (Ri) you can control the heater supply voltage so that the
temperature of the sensor is kept at a nominal temperature of approx. 750°C
which is needed for *precise* measurements.

The Nernst-cell internal resistance is measured by pulsing the Nernst-cell via a
capacitor and a resistor.The pulsing must be done between 1kHz and 4kHz.(CJ120 3kHz).

On the Tech Edge Pty. Ltd. schematic you can see that they measure the Nernst-cell
internal resistance and also measure the effective heater voltage and current.

On the CJ120 block diagram you can see that the effective heater voltage and
current are not measured. The document http://wbo2.com/lsu/Y258K01005e03mar21eng.pdf
describes the maximum permissible heat up rate when the heater is switched on.
When you know the Nernst-cell internal resistance then you can control the heater
without measuring its voltage and current.

Luciano

[toalan]

I have read the datasheet on the sensors many times before.

My original circuit had PID control of heater to maintain the 80 ohm resistence on the nermest Cell with a 3 khz ac signal, I made a mistake in my previous post about the 80 ohms in the pump cell when it should of been the nermest cell.

[toalan]

I just looked at the tech edge diagrams in detail, everythin looks fine a dandy except I did not notice a coupling capacitor to couple the 3 khz AC signal to sense the Nermest resistance, the "VsDrive" connection connects through a resistance (910 ohms) to pin 11 of the atmel8 AVR MCU, if you are coupling an AC signal of 0v to 5v then for the bosch lsu you would need something in the 10k range and also a capacitor. Also Pin 11 of the atmel8 AVR is not a PWM pin, if he is ouputing an AC signal he must be doing it via software.

I am thinking that the TE unit actually powers off the sensor and does DC sensing of the the resistence in the nermest cell, which would make the unit super slow.

I am jsut puzzled because no where on the schematic are any hallmarks of generating an ac signal, coupling an ac signal into the nermest cell, or low pass filtering to target a signal in the 3khz range. The only filtering around the VS port are low pass filters with a 3bd freq of about 10khz.

[Luciano]

Hi,

See attached BMP file.

Nernst-cell internal resistance (Ri) measurement.

The circuit measures the resistance of the Nernst-cell and
also the resistance of the RiCall 82.5 ohm. Both measurements
are done with the same I/O, so we measure with the same voltage
when we source (+4.xx V) and when we sink (0.xx V).
The PWM is not used.

The AC current is ≤ 250 µA.
(See 250 µA current direction when the I/O sink or source).

The differential amplifier will output a voltage when
Ri and RiCall have different values.The output voltage is
measured with the A/D of the MCU. With the resistors you
can adjust the gain of the amplifier.

* * *

The Tech Edge does almost the same with the I/O but
they use a 910 ohm resistor so the current is more
than 250 µA. (???). The capacitor is the 100nF C201.
They use 2V as the virtual ground.

(See page 6 of the PDF for Max. current load of the Nernst-cell).
http://wbo2.com/lsu/Y258K01005e03mar21eng.pdf

* * *

This is just a theoretical circuit.
Never been tested.

Luciano