L9780 datasheet(15/56 Pages) STMICROELECTRONICS

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L9780

Main functionalities

Figure 4. Typical sensor N compensation network

Figure 5. Typical sensor B compensation network

Typical ranges for integrator amplifier electrical parameters are specified in Table 15.

4.8

Pin FV, FVOUT functionalities: FVOUT amplifier

C3 pin voltage is the VCCS direct input control voltage. Thanks to the presence of the

external capacitor on FV pin (CFV, specified in Table 19) and the internal resistance RFV

(typical value 5 kΩ and possible range specified in Table 11), on FV pin the low pass filtered

C3 voltage can be measured. FV voltage is the input of the FVOUT amplifier used to provide

on FVOUT pin a signal range compatible with an external A/D converter, as follows:

FVOUT = REF2 + G * (FV – REF2)

Where G is the gain of VOUT amplifier selectable via SPI (using bits SAMP[2..0]) among the

following values: 1 - 1.5 - 2 - 3 - 4 - 6 - 8 – 12. A sample and hold circuitry and the offset

compensation technique are used in the architecture of FVOUT amplifier; for this cell all the

electrical parameters are specified in Table 10 and Table 15.

4.9

Pin TG1, TG2, OUT1, OUT2, SNS functionalities: the VCCS

TG1, TG2, OUT1, OUT2, SNS are the interface pins between VCCS structure and the

external pump cell. The pump cell allows to control the oxygen concentration by forcing an

electric current through the cell itself; in other words it is possible to control the direction and

the intensity of oxygen transport, because it is directly related to the direction and the

intensity of the current. By controlling the amount of current through the pump cell, it is

possible to control the amount of oxygen and consequently the λ parameter of the sensor;

closing this mechanism into a loop, like in L9780, it is possible to regulate the pump cell

current in order to obtain the target λ = 1. The best working condition for the sensor is the

high temperature; in this condition the AC impedance of the pump cell can be assumed to

be a large capacitance in series to with a resistor of about 20-30 Ω. When cold, the pump

cell can be assumed to be an open circuit.

GAPGPS01860

L9780 Datasheet(PDF) 15 Page - STMicroelectronics