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TDA5153AG

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

TDA5153

SYMBOL

PARAMETER

tst(W)

write settle times; note 12

toff(W)

write amplifier off time

tsw(W)

tsw(S)

head switching (in write mode),

and standby to write head active

sleep to (and from) any other

modes

DC characteristics

ICC(R)

ICC(W)

supply current; note 13

supply current; note 14

IDD(stb)

IDD(S)

Vref

standby mode supply current

sleep mode supply current

reference voltage for Rext

CONDITIONS

MIN.

from 50%of the falling edge of −

R/W to 90% of the steady state

write current (in Write Mode)

from rising edge of R/W to

−

IWR-programmed /10

(IWR = 35 mA)

from falling edge of SEN to

−

write head active

−

TYP.

−

−

50

−

MAX.

70

50

70

100

UNIT

ns

ns

ns

µs

read mode; IMR = 10 mA

−

72

80

mA

write mode; IWR = 35 mA

from VCC (5 V)

−

33

41

mA

from VCC(WD) (5 to 8 V)

−

54

61

mA

−

0.25 1

mA

static

−

0.025 −

mA

−

1.32 −

V

Notes to the characteristics

1. The differential voltage gain depends on the MR

resistance. It can be improved by programming the

d4 bit in the configuration register using the serial

interface.

2. The gain boost implements a pole-zero combination:

The +3 dB gain boost corner frequency is

--(--8-----⋅---d----3-----+-----4----⋅--8-d--0--2-0----+-M----2-H----⋅-z--d----1-----+----1-----⋅---d----0----)-

The −3 dB gain attenuation corner frequency is

--(--8-----⋅---d----3-----+-----4----⋅--8-d--0--2-0----+-M----2-H----⋅-z--d----1-----+----1-----⋅---d----0----)-

where d3, d2, d1, d0 are bits (0, 1) to be programmed

via the Serial Interface. In practical use, the bandwidth

is limited by the inductance of the connection between

the MR heads and the pre-amplifier.

3. Noise calculation

a) Definitions: The amplifier has a low-ohmic input.

No lead resistance is taken into account. The input

referred noise voltage, excluding the noise of the

MR resistors, is defined as follows:

Vnir2

=







V--G---n-v-o-







2

–

4kT

×

(RMR1 + RMR2)

V

where Gv is the voltage gain and Vno is the noise

voltage at the output of the amplifier, k is the

Boltzmann constant and T is the temperature in K.

The noise figure is defined as follows:

F

=





10

×





log



4----k----T-----×------(--R-----V--GM------n--R-v-o----1----2+-----R----M----R----2---)-











dB





in 1 Hz bandwidth. Note that RMR includes all

resistances between Rx or Ry to ground.

b) Noise figure versus IMR and RMR: Table 1 shows

the variation of the noise figure with IMR (mA) and

RMR (Ω).

c) Input noise voltage consideration: the input

referred noise voltage calculation can significantly

be different (from 1.0 to 0.44 nV/√Hz for instance)

by taking into account an equivalent

signal-to-noise ratio when using two MR stripes

(28 Ω for each stripe) or one MR stripes (42 W).

It assumes that the signal coming from the head is

larger for a dual stripe head than for a single stripe

head (50% extra signal for dual stripe head).

4. The channel separation is defined by the ratio of the

gain response of the amplifier using the selected head

H(n) to the gain response of the amplifier using the

adjacent head H(n ±1), Head H(n) being selected.

1997 Jul 02

21

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