AN2738 datasheet(14/54 Pages) STMICROELECTRONICS

14 / 54 page

L6390 op-amp

AN2738

14/54

Doc ID 14589 Rev 2

Figure 11.

General advanced current sense scheme

Principle waveforms corresponding to the above scheme are provided in Figure 12:

Figure 12.

Advanced current sensing waveforms

ADCs used in vector control applications have a typical FSR of about 3.3 V. The sense

signals have to be shifted and centered on FSR/2 voltage (about 1.65 V) and amplified with

a gain which provides the matching between the maximum value of the sensed signal and

OP+

OP-

OPOUT

OPAMP

H.V.

TO LOAD

VREF

to ADC

COUT

ROUT

Half-Bridge

Current Sensing

Voltage Shifting

of the Vsense

Vsense

Voltage Gain

and

Filtering

Capacitor required

by the ADC

for sampling purpose

ROUT resistor is usually required

in order to make the OPAMP stable

when the COUT capacitance increases

OP+

OP-

OPOUT

OPAMP

H.V.

TO LOAD

VREF

to ADC

COUT

ROUT

Iload x Rs

-Iload x Rs

0.6 V

3.3 V

FILTERED SIGNAL

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