SA56202 Datasheet, PDF (7/24 Pages) NXP Semiconductors – One-chip motor driver

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
V_DD(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
R_LIM
maximum
motor
current
R_EMF
motor
k-factor
ANALOG DOMAIN
DIGITAL DOMAIN
A
V_RI = R_m × I_m
D
A
D
V_MOT = V_RI + V_EMF
PWM
V_EMF = 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 V_EMF. This V_EMF is added to the current-limit
scaled spindle input voltage V_VINSPN. This sum V_MOT steers the PWM outputs U, V and W.
The result is that the input voltage V_VINSPN 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.
V_M1
V_RM
V_EMF
2
V_RM
V_EMF
2
V_M2
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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