TDA5345HT Datasheet, PDF (16/44 Pages) NXP Semiconductors – 5 V spindle & VCM driver combo

Philips Semiconductors
5 V spindle & VCM driver combo
Preliminary specification
TDA5345HT
programmed to be the maximum allowable delay value.
If ∆Zc_measured is lower than ComDeLim, the next commutation delay will be ∆Zc_measured divided by 2.
If ∆Zc_measured is higher than ComDeLim, the next commutation delay will be ComDeLim value divided by 2.
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
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
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.
17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
StartUp
WatchDog
Blank
Fig.9 Timer 1 configuration.
Calculations:
The actual delay will be: Delay = (Value * Step) + min, where:
Value
= the decimal value programmed in the considered register
Step size
= 2^LSB / ClockOutPrescaler
Min
= (2^LSB -1) / ClockOutPrescaler (bits from 0 to (LSB-1) are internally set to 1)
maximum
= (2^(MSB+1) -1) / ClockOutPrescaler
1999 June 10
16