AN1139 STMicroelectronics, AN1139 Datasheet - Page 52

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AN1139

Manufacturer Part Number
AN1139
Description
L6254 - L6268 - L6269 12V DISK DRIVE POWER COMBO IC
Manufacturer
STMicroelectronics
Datasheet
AN1139 APPLICATION NOTE
8.1.2 Spindle Speed Control Loop
Figure #36 shows the Spindle Speed Control Loop model used for the analisys. Figures 37a, 37b, 37c show the
Mathcad analisys of the loop.
Figure 36. Spindle Speed Control Loop
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Fref
Fref
Kfll
Ifll
As
Rs
Gm
Km
Jm
Rc
Cc1
Cc2
25 10
. 3 10
0.2
0.43 10
4
As Rs
125
1
. 1 10
0.1 10
90
.
1
.
.
.
1
6
6
6
.
Kfll
6
Ifll
Fref
Reference Clock Frequency(Hz) Speed at 5400Rpm
*Charge Pump Current Gain(1or4)
Charge Pump Current(A)
*Sense Amp Gain
*Sense Resistor(0.3ohms)
Current Loop Transconductance(A/V)
*Motor Torfque Constant(gm-cm/A)
*Motor Inertia(gm-cm-sec-sec)
*FLL Compensation Resistor
*FLL Compensation Capacitor
*FLL Compensation Capacitor
Cc1
Rc
Zfilter
Cc2
AsRs
1
Gm
S*Jm
Km
Ifll 2.5 10
=
Gm 0.833
2*pi
1
=
5
Fm

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