TDA5155 Просмотр технического описания (PDF) - Philips Electronics

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TDA5155

Pre-amplifier for Hard Disk Drive (HDD) with MR-read/inductive write heads

Philips Electronics 

Philips Semiconductors

Pre-amplifier for Hard Disk Drive (HDD)

with MR-read/inductive write heads

Preliminary specification

TDA5155

8.7.5.3 Thermal asperity detector

d2 = logic 1, d1 = x, d0 = (0,1). Unlike the above tests, the

thermal asperity detection does not use the RDx and RDy

outputs. Thus, the reader is fully operational. In case a

thermal asperity is detected, it is flagged at the HUS pin.

The threshold voltage for the thermal asperity detection is

2-bit programmable. These 2 bits consist of d0 (LSB) of

the test mode register (address = 0xxx0110), and d2 of the

compensation capacitor register (address = 0xxx0111).

Vth = (210 + 560.d0 + 280.d2) µV

d0 of test mode register;

d2 of the compensation capacitor register.

8.7.6 WRITE AMPLIFIER PROGRAMMABLE CAPACITORS

By default (d2 = d1 = d0 = logic 0) the programmable

capacitors are zero. These capacitors are used to improve

the performance of the write amplifier according to the

write amplifier output load.

8.7.7 HIGH FREQUENCY GAIN ATTENUATOR REGISTER

By default (d3 = d2 = d1 = d0 = logic 0) the high frequency

gain attenuator is not active. The gain attenuator provides

a pole which limits the bandwidth and reduces the high

frequency noise. The HF pole can be used in combination

with the HF zero in order to boost the HF gain locally and

yet limit the very high frequency noise enhancement.

8.7.8 HIGH FREQUENCY GAIN BOOST REGISTER

By default (d3 = d2 = d1 = d0 = logic 0) the high frequency

gain boost is not active.

The gain boost provides a zero which allows to optimize

the bandwidth of the read amplifier and to correct for

attenuation caused by series inductances in the leads

between the MR heads and the read amplifier inputs.

8.7.9 SETTLE PULSE

By default (d2 = d1 = d0 = logic 0) the settle pulse has a

nominal duration of 3 µs. Its value can be programmed

from 2.125 µs to 3 µs according to the following formula:

tst = 2µs + -(---4---.--d----2-----+-----2---.--d----11-----+-----1---.--d----0-----+-----1---)--µs

The settle pulse is used to shorten the transients during

switching.

8.7.10 ADDRESS REGISTERS SUMMARY

ADDRESS REGISTERS(1)

A7 A6 A5 A4 A3 A2 A1 A0

FUNCTION

0 X X X 0 0 0 0 configuration register:

d0 = 0: use data flip-flop; d0 = 1: by-pass data flip-flop

d1 = 0: WDI PECL; d1 = 1: current input

d2 = 0: write current inhibit active; d2 = 1: write current inhibit inactive

read mode: d3 = 0: HUS active; d3 = 1: HUS HIGH

write mode: d3 = 0: HUS active; d3 = 1: HUS LOW

d4 = 0: read gain nominal; d3 = 1: read gain +3 dB

d5 = 0: read amplifier OFF during write mode; d5 = 1: read amplifier ON

during write mode

0 X X X 0 0 0 1 power control register:

(d1,d0) = (0,0): sleep mode

(d1,d0) = (1,0) or (0,1): standby mode

(d1,d0) = (1,1): active mode (write or read)

0 X X X 0 0 1 0 head select register:

(d3,d2,d1,d0) = (0,0,0,0) to (1,0,0,1): H0 to H9

addressing H10 to H15 causes HUS to go HIGH if in write mode and H0 to be

selected if in read mode

1997 Apr 08

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