SA56202 데이터 시트보기 (PDF) - Philips Electronics
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SA56202 Datasheet PDF : 24 Pages
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Philips Semiconductors
SA56202
One-chip motor driver
driver do not use this recuperated current, than the supply voltage can possibly rise to
unacceptable values. In that case it is recommended to lower the spindle current during
brake by means of the VINSPN setting.
Upon detection of reverse detection all U, V and W driver outputs are connected to
VDD(SPN). This short brake prevents the motor of spinning backwards.
7.2 Internal regeneration of back-EMF spindle motor
The spindle motor driver uses the information from the Hall sensors to internally
regenerate the back-EMF of the motor. See Figure 4.
VINSPN
torque
control
signal
RLIM
maximum
motor
current
REMF
motor
k-factor
ANALOG DOMAIN
DIGITAL DOMAIN
A
VRI = Rm × Im
D
A
D
VMOT = VRI + VEMF
PWM
VEMF = ω × k
ω
SPEED
A
D
U
V
W
Hall U
Hall V
Hall W
spindle
motor
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Fig 4. Regeneration of back-EMF voltage spindle motor.
Rotational speed ω is derived from the Hall event frequency. Multiplying ω with the k-factor
of the motor gives the back-EMF voltage VEMF. This VEMF is added to the current-limit
scaled spindle input voltage VVINSPN. This sum VMOT steers the PWM outputs U, V and W.
The result is that the input voltage VVINSPN sets the current through the motor. This
explains how the SA56202 spindle motor driver exhibits a current control transfer function
without using external sense resistors.
The simplified motor schematic in Figure 5 shows the series resistance and back-EMF
voltage of the motor.
VM1
VRM
VEMF
2
VRM
VEMF
2
VM2
Fig 5. Simplified spindle motor schematic.
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9397 750 12772
Preliminary data sheet
Rev. 01 — 19 July 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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