SLFS040

– DECEMBER 1993

POST OFFICE BOX 655303

DALLAS, TEXAS 75265

13

PRINCIPLES OF OPERATION

spindle-driver system (continued)

For active braking, all the spindle low-side drivers are disabled and the high-side drivers are enabled, thereby

spindle commutation

Hall- or back-EMF-spindle commutation is selected from serial port C. See the port-C system control bit

definitions in Table 6 for additional information.

Hall mode

In the Hall mode, the spindle position information is input to the TLS2205 via the HU, HV, and HW logic input

terminals. Start current can be controlled with the internal 8-bit DAC, which is normally used to control the VCM

current or the internal charge pump. If the DAC option is selected, the VCM driver is normally disabled during

spindle start for power conservation. In either case, the spindle motor starts without microprocessor

intervention.

back-EMF mode

For the back-EMF mode, the system microprocessor is used in conjunction with the TLS2205 internal circuitry

to start the spindle motor.

Start current is controlled the same way as in the Hall mode by using the DAC. Two schemes can be used to

start commutation in the back-EMF mode. The first scheme is to use AUXIN; this method requires a pulse

generated from the microprocessor as an input signal to AUXIN. Various frequencies and start currents are used

to start the spindle motor. The second scheme is to use the COMM bit (bit 4) in port C. This method requires

the microprocessor to write to port C to change the state of bit 4. For every 1-to-0 state change of

bit 4, the spindle inverters advance one state. Different frequencies and start currents are used to start the

spindle motor. Once the motor has reached approximately 10% of its rated speed, the TLS2205 may be switched

into the run mode via port C.

Figure 4 shows the TLS2205 commutation delay circuit and the required external components.

_

+

_

+

2 V

100 mV

NHphase

COMDLY 2

Vref

Rcom2

Ccom2

Ccom1

Rcom1

COMDLY 2

VPHASE

Figure 4. Commutation Delay Circuit

This circuit is composed of an operational amplifier (OPA) followed by a hysteresis comparator. The TLS2205

spindle inverter is advanced for every transition of the NHphase signal. The transition of NHphase occurs every

defined as:

Rcom1

– Integrator gain-set resistor

Ccom1

– DC-blocking capacitor

Rcom2

– Integrator dc-set resistor

Ccom2

– Integrator gain-set capacitor