AN1625 datasheet(30/39 Pages) STMICROELECTRONICS

30 / 39 page

AN1625 APPLICATION NOTE

30/39

Figure 32. Speed response to a 1mNm resistant torque step

Figure 33. Speed response to a 1V speed voltage step.

2.15.3 Loop Stability:

The phase margin is defined as 180° minus the phase of Gloop at the cut frequency (where Gloop=1). It should

be at least 45° to guarantee the stability. In the example it's about 65°.

2.15.4 Reference voltage ripple:

Due to the tacho waveform integration, the reference voltage provided to the L6235 Vref input is a triangular

wave (see Figure 27). The ripple can be calculated through the approximate relation:

where DC is the duty-cycle of the square wave at the tacho output:

Since this reference voltage is the torque control voltage, the ripple should be kept as low as possible,

accordingly to others main parameters. In the example the ripple is about 60 mV.

0.1

0.2

0.3

0.4

0.5

0.6

0.7

100

t [s]

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1600

3200

4800

6400

8000

t [s]

∆V

re f

speedref

–

()

⋅

fb1

tacho

⋅⋅

------------------------------------------------------

--------------------

⋅

pul se

⋅⋅

-----------------------------------

AN1625 Datasheet(PDF) 30 Page - STMicroelectronics

AN1625 Datasheet(HTML) 30 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

Datasheet Download

Link URL