Browse Prior Art Database

Flexible Applied Write Voltage for Disk Drive Preamplifier

IP.com Disclosure Number: IPCOM000109046D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 52K

Publishing Venue

IBM

Related People

Kerwin, GJ: AUTHOR [+3]

Abstract

A method for providing enhanced write performance in a disk drive preamplifier with increasing power supply voltage is disclosed. The write driver topology is so configured that all increases in the positive power supply voltage are applied to the recording head write coil during a write operation.

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Flexible Applied Write Voltage for Disk Drive Preamplifier

      A method for providing enhanced write performance in a disk
drive preamplifier with increasing power supply voltage is disclosed.
The write driver topology is so configured that all increases in the
positive power supply voltage are applied to the recording head write
coil during a write operation.

      The circuit in the figure is a depiction of a disk drive write
driver. Typically, the WRITE DATA signal is applied to inputs
PDATA/MDATA as current pulled out through resistors RX1 and RX2.  The
voltage developed across these resistors is applied to input
transistors Q1 and Q2. Obviously, if VCC is increased, the common
mode voltage at PDATA/MDATA also increases.  If these voltages were
applied directly to the driver at nodes PWD/MWD, there would be no
increase in headroom for Q10 and Q12 as VCC increases.  The extra
voltage would appear instead as headroom for current source IWRITE.

      In the enhanced write driver circuit, PNP transistors Q4 and Q5
are used to down-shift the write data signal.  The resulting signal
voltages at nodes PWD/MWD are referenced to voltage VREF, rather than
to VCC.  VREF is made to track GND; therefore, the common mode
voltage at PWD/MWD remains constant as VCC changes, and any increase
in VCC is applied as additional voltage headroom across the
collector-base junctions of Q10 and Q12.  The additional headroom
means additional compliance voltage for driving th...