tda5155 NXP Semiconductors, tda5155 Datasheet - Page 21

• Manufacturer Part Number: tda5155
• Description: Pre-amplifier For Hard Disk Drive Hdd With Mr-read/inductive Write Heads
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Notes to the characteristics
1. The differential voltage gain depends on the MR
2. The gain boost implements a pole-zero combination:
3. Noise calculation
4. The channel separation is defined by the ratio of the
1997 Apr 08
Pre-amplifier for Hard Disk Drive (HDD)
with MR-read/inductive write heads
resistance. It can be improved by programming the
d4 bit in the configuration register.
The +3 dB gain boost corner frequency is
attenuation corner frequency is
are 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.
a) Definitions: The amplifier has a low input
b) Noise figure versus I
c) Input referred noise voltage: The input referred
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.
-------------------------------------------------------------------- -
8.d3
-------------------------------------------------------------------- -
8.d3
resistance. No lead resistance is taken into
account. The input referred noise voltage,
excluding the noise of the MR resistors, is defined
as:
where G
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:
bandwidth. Note that R
between Rx or Ry to ground.
the variation of the noise figure with I
noise voltage calculation can be significantly
different (from 1.0 to 0.44 nV/ Hz for instance) by
taking an equivalent signal-to-noise ratio into
account when using two MR stripes (28
stripe) or one MR stripe (42 ). 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 a dual-stripe head).
F
+
+
=
4.d2
4.d2
V
10
800 MHz
800 MHz
irn
v
+
+
2
is the voltage gain, V
log
2.d1
2.d1
=
----------------------------------------------------------- -
4kT
V
-------- -
G
+
+
no
v
1.d0
1.d0
2
MR
–
R
MR
. The 3 dB gain
, where d3, d2, d1 and d0
V
-------- -
4kT
G
MR1
and R
no
v
includes all resistances
2
+
R
no
MR
R
MR2
is the noise
MR1
: Table 1 shows
MR
+
in 1 Hz
R
and R
MR2
for each
MR
,
.
21
5. The PSRR (in dB) is defined as input referred ratio:
6. This refers to the crosstalk from SCLK and SDATA
7. The rise and fall times depend on the
8. The write current rise/fall time asymmetry is defined by
9. Write-to-read recovery time includes the write mode to
10. In read mode, the head switching, standby to read
11. Write settling time includes the read mode to write
12. The typical supply current in read mode depends on
13. The typical supply current in write mode also depends
to differential output gain, and G
to differential output gain.The CMRR (in dB) is defined
as input referred ratio:
G
G
gain. Flex and board lay-out may affect these
parameters significantly.
inputs via the read inputs to RDx and RDy. Two cases
can be distinguished:
a) When SEN is LOW, SCLK and SDATA are
b) Programming via the serial interface is done with
write amplifier/write head combination. L
represent the components on the evaluation board.
Parasitic capacitances also limit the performance.
read mode switching using the R/W pin on the same
head (see Fig.5). The AC signal reaches its full
amplitude few tens of ns after appearing at the reader
RDx and RDy outputs.
active switching and changing MR current include fast
current settling (see Fig.5). The AC signal reaches its
full amplitude few tenth of ns after appearing at the
reader RDx and RDy outputs.
mode switching using the R/W pin.
the bias current for the MR element.
on the write current.
PSRR
---------------------- -
2 t
v
cm
is the differential input to differential output gain and
t
prohibited reaching the device and crosstalk is low.
SEN HIGH. Then crosstalk can occur. A careful
design of the board or flex-foil is required to avoid
crosstalk via this path.
r
is the common mode input to differential output
r
–
+
t
f
=
t
f
20 log
G
------ -
G
v
p
, where G
CMRR
Preliminary specification
=
v
is the differential input
p
20 log
is the power supply
TDA5155
h
---------- -
G
G
and R
cm
v
, where
h