1998 July 30
Philips Semiconductors Objective Specification, Revision 2.2
Pre-Amplifier for Hard Disk Drive with
MR-Read / Inductive Write Heads TDA5360
21
Formula to link real TAD threshold with LF pole of the reader and programmed input impedance :
where : fLFP is the low frequency pole of the read amplifer (1 to 4 MHz, programmable via Reg. 03)
fTA is the frequency of the principal harmonic of the TA signal.
and :
where : RINnom is the input impedance of the reader in mid-band (programmable via Reg. 01)
For RINnom = 18Ω, RMR = 66Ω, fTA = 2MHz, Tj = 70oC, we have K = 0.214
and so, Vth( fLFP = 1MHz) = Vthprog * 1.747
Vth( fLFP = 4MHz) = Vthprog * 0.945
Note 7: FAULT code protocol.
When a fault occurs, the FAULT pin is set LOW (if read mode) or HIGH (if write mode) and a 4 bits code is
available in Reg. 07 (See Section 10.2 for details).
The FAULT pin is flagged as long as the error remains present. When the error condition is removed, the
FAULT pin toggles to a non-error state, but the 4 bits code still remains present in Reg. 07
To Reset the FAULT code, the user should reprogramm Reg. 09.
Some fault detections can be inhibited via FLT2,1,0 bits. If an action is linked to the inhibited detection (for
example inhibiting the write current when a low power supply condition occurs), then the action is still taken,
but no fault code and no FAULT pin toggling occurs.
Note 8 : RMR and Temperature Digitizer
- RMR digitizer
This measurement can only be done in Read mode, with the head to be measured selected.
the Digitazation is launched when DIGON toggles from LOW to HIGH,
after a maximum of TBD us, a 5 bits code is available in Reg. 08.
The 5 bits code will only be reseted by DIGON toggling from HIGH to LOW.
VthVthprog0.85
K
1fLFP
KfTA×()
------------------------
2
+
1fLFP
fTA
-------------
2
+
-------------------------------------------×
----------------------------------------------------------×=
KRINnom
RINnomRMR+
-----------------------------------------=