1997 Jul 02

21

Philips Semiconductors

Preliminary specification

Pre-amplifier for Hard Disk Drive (HDD)

with MR-read/inductive write heads

TDA5153

write settle times; note 12

from 50%of the falling edge of

R/W to 90% of the steady state

write current (in Write Mode)

−−

70

ns

write amplifier off time

from rising edge of R/W to

−−

50

ns

head switching (in write mode),

and standby to write head active

from falling edge of SEN to

write head active

−

50

70

ns

sleep to (and from) any other

modes

−−

100

µs

DC characteristics

supply current; note 13

−

72

80

mA

supply current; note 14

−

33

41

mA

−

54

61

mA

standby mode supply current

−

0.25

1

mA

sleep mode supply current

static

−

0.025

−

mA

−

1.32

−

V

SYMBOL

PARAMETER

CONDITIONS

MIN.

TYP.

MAX.

UNIT

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

The

−3 dB gain attenuation corner frequency is

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:

voltage at the output of the amplifier, k is the

800 MHz

8d3

⋅

4d2

⋅

2d1

⋅

1d0

⋅

+++

()

-------------------------------------------------------------------------------------

800 MHz

8d3

⋅

4d2

⋅

2d1

⋅

1d0

⋅

+++

()

-------------------------------------------------------------------------------------

V

nir

2

V

no

G

v

---------





4kT

R

MR1

R

MR2

+

()

×

V

–

=

Boltzmann constant and T is the temperature in K.

The noise figure is defined as follows:

resistances between Rx or Ry to ground.

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.

F

10

log

V

no

G

v

---------





4kT

R

MR1

R

MR2

+

()

×

------------------------------------------------------------













×

dB

=