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1998 July 30
Philips Semiconductors Objective Specification, Revision 2.2
Pre-Amplifier for Hard Disk Drive with
MR-Read / Inductive Write Heads
TDA5360
20
Note 0 : MDS (Multiple Device Selected) detector :
When several preamps are connected in parallel, this function allows the user detection of wrong adressing
withing the preamps.
When SELT is high, the selected preamp pull a precise current on FLT pin. If only one preamp has reacted,
SELF is LOW. If more than one preamp has reacted, the voltage on FLT pin is lower than a reference voltage
and thus SELF is HIGH.
Note 1a : The Write path can be controled by either a voltage or a current input signal.
The signal polarity is non inverted from WDP - WDN input to WPx - WNx output
Voltage mode : WDP-WDN > 0 => WPx-WNx > 0 (current flowing externally from WPx to WNx)
Current mode : current has to be pulled from WDP and WDN pins.
The positive side for signal, is the one where the least current is pulled
The negative side for signal, is the one where the most current is pulled
most current pulled from WDN => current flowing externally from WPx to WNx)
Note 1b : BFCTL define BFAST functionality :
See ENFST bit in Reg. 11 for restrictions of BFAST functionality
Note 3 : For differentiator only (GAIN0 = GAIN1 = 1),
the midrange setting ( HFZ3 = 1, HFZ0 = HFZ1 = HFZ2 = 0 ) have a gain of 44dB at 100 Mhz.
i.e. gain (@100 Mhz)= 80 +10 * (HFZ0 + 2*HFZ1 + 4*HFZ2 + 8*HFZ3)
For gain plus differentiator (other GAIN0, GAIN1 programmation)
the midrange setting (HFZ3=1, HFZ0,1,2=0) create a zero at 300 Mhz independent of the gain bits.
HF Zero @ f = 2400 MHz / (HFZ0 +2*HFZ1 + 4*HFZ2 +8*HFZ3)
i.e. gain = 150 + 75 * ( GAIN0 + 2*GAIN1 - 5*GAIN0*GAIN1)
Note 4 : In order to increase performance for high data rate, 3 bits are available to tune the write current waveform.
WCP2 : this bit is used to add a capacitive boost during a transition of the write current.
WCP1,WCP0 : these bits are used to increase the internal swing on the write data signal.
when IW4 is HIGH ( Iwr > 30.8 mA), some capacitive compensation is also activated in the write driver.
Note 5 : The threshold range of the TAD can be shifted up by 50% by setting TRANGE HIGH.
In that case the steps are still 177uV,
but the range is shifted from ( 0.390mV-5.877mV ) to ( 3.560mV-9.047mV )
The relation between the threshold of the TAD programmed in Reg. 05 and the real threshold is a function of
the input impedance of the reader and the low corner frequency of the reader.
BFCTL BFAST Function
LOW LOW I
MR
generator ON (Reader ON) during write
LOW HIGH I
MR
generator OFF (Reader OFF) during write
HIGH LOW Normal Reader PassBand
HIGH HIGH Low Frequency corner increased to 8 MHz