1999 June 10

16

Philips Semiconductors

Preliminary specification

5 V spindle & VCM driver combo

TDA5345HT

programmed to be the

maximum allowable delay value.

If

If

ComDeLim can be limited to guarantee a faster lock after the motor has gone out of lock.

The clock used in the commutation control block is obtained by dividing the master clock of the chip (CLOCK: pin #38)

by a clock divider (PRESCALER). This internal clock is named ClockOutPrescaler.

All the delays described above (Blank, WatchDog and StartUp) are generated by a down-counter (called TIMER1). The

time between two zero-crossings is measured by a second counter called TIMER2. The commutation delay and the

ComDeLim are derived from TIMER2. Both counters are clocked on ClockOutPrescaler clock, which is programmable

through the serial interface, using bit 7 & 8 of register #0: (ClockOutPrescaler should be chosen as typically 1 MHz)

Table 4

Clock configurations

TIMER

1

Timer 1 is used to generate Blank, WatchDog and StartUp delays: It loads one of these programmed values and counts

down till it reaches zero. All LSB bits are internally set to ‘1’: bits [2:0] for Blank, bits [8:0] for WatchDog, bits [13:0] for

StartUp.

Calculations:

The actual delay will be: Delay = (Value * Step) + min, where:

Value

= the decimal value programmed in the considered register

Step size

ClockOutPrescaler

Min

ClockOutPrescaler (bits from 0 to (LSB-1) are internally set to 1)

maximum

ClockOutPrescaler

PRESCFACTOR1

(BIT 8, REG#0)

PRESCFACTOR0

(BIT 7, REG#0)

CLOCKOUTPRESCALER

0

0

CLOCK/4

0

1

CLOCK/8

1

0

CLOCK/16

1

1

CLOCK/32

Fig.9 Timer 1 configuration.

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

Blank

WatchDog

StartUp