SA56202 Datasheet, PDF (6/24 Pages) NXP Semiconductors – One-chip motor driver

Philips Semiconductors
SA56202
One-chip motor driver
Table 2:
Symbol
VINTLT
VINTRK
VINFCS
VINLD
V_SS(DIO)
DIODE
COSC
Pin description …continued
Pin
Description
50
tilting driver input for tilt actuator voltage
51
tracking driver input for tracking actuator voltage
52
focus driver input for focus actuator voltage
53
loading driver input for loading motor voltage
54
temperature diode ground
55
diode for temperature readout
56
external capacitor for internal oscillator
7. Functional description
7.1 Spindle motor control
The control input voltage on pin VINSPN is converted into a digital value by the ADC
where the voltage on pin VINREF is the midpoint reference. The transconductance gain
from input voltage V_VINSPN to output motor current I_MOT is:
g_{m(SPN )} = _V-----_V---_I--_N---_S---_P---^I_N--^M---_–-^O---_V-^T----_V---_I--_N---_R---_E---_F- = _V-----_V-^I--_IL--_N-^I--^MR---_E---_F--
where I_LIM can be programmed by means of external resistor R_LIM; see Section 7.4. The
motor current is described by Figure 3.
I_LIM
I_MOT
0
reverse
torque
brake
V_VINREF
forward
torque
2V_VINREF
−I_LIM
V_VINSPN
001aaa431
Fig 3. Spindle motor current as a function of control input voltage on pin VINSPN.
For VINSPN voltages larger than V_VINREF the motor will accelerate with forward torque
control. For VINSPN voltages smaller than V_VINREF the motor will brake with reverse
torque control. Because the U, V and W half-bridges of the spindle motor driver use a
direct PWM full-bridge switching scheme, the motor current can also be controlled and
limited during brake. Note that because of this active brake mechanism energy of the
motor can be recuperated back to the supply. Especially at large speeds, this can result in
currents delivered back to the supply. If the supply and/or other circuits than the motor
9397 750 12772
Preliminary data sheet
Rev. 01 — 19 July 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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