IC with a

programmable threshold, which is set

by an external resistive divider. The TTL compat-

ible output can be used separately or connected

to Park input in order to park the head.

PARKING CIRCUIT OPERATIONT

The voice coil driver is switched into the parking

condition when Power on Reset output or Park in-

put are low. In such a condition a fixed voltage is

superimposed on the load and the value of such a

voltage is set by connecting an external resistor

between

Park

Voltage

Program

input

and

ground: (Vpark=Rext x Iref, Iref=100

µA typ). Con-

necting ENABLE input to GND the driver will be

disabled (outputs in high impedance mode).

THERMAL SHUTDOWN

It will disable the IC when the junction tempera-

ture exceeds the threshold value above which the

device could be damaged.

FUNCTIONAL DESCRIPTION (continued)

Function

Description

This is the Power Supply input.

POWER FAIL

THRESH

Output

THRESHOLD.

LOGIC SUPPLY

SENSE input

This pin allows the monitoring of 5V supply. When a low voltage is detected POR is asserted

PARK POWER

input

This input is used during the Power Down/Power Fail Parking operation. When the supply goes

down, a typical Spindle Driver Circuit automatically tristates its output stages. During this time

the spindle motor spins freely and the stored energy is used to drive the VCM to the park

position. The generated BEMF is rectified and filtered across an external PARKING

CAPACITOR.

PROGRAMMABLE

PARK VOLTAGE

input

Used to set the voltage applied to the VCM during an Automatic Parking Operation.

PARK

input

Logic signal asserted low, activates parking.

POWER ON RE-

SET output

Indicates an error condition to the external control and support circuitry. A Logic Supply Fail

condition automatically initiates a POWER ON RESET. Internal 30k Pullup to LSS.

POWER ON RE-

SET DELAY

in-

put

The intent of this input is to provide a time delay at power up. During this time, the POWER ON

RESET line will be asserted (low). A POWER ON RESET, will hold the system in the PARK

mode.

Once the delay has timed out, the POWER ON RESET will be removed to allow the

external system to assume control. When applied in a Disk Drive Application, the POWER ON

RESET DELAY will be required to have a minimum duration which will ensure that the

Read/Write Heads can be fully parked.

ENABLE

input

This signal originates at the external controller and, when asserted, allows the VCM Drivers to

operate. When deasserted the VCM Driver is forced into Tristate mode. During a POWER ON

RESET condition however, the parking operation is automatic and takes priority over the

ENABLE function. Only at the end of the POWER ON RESET DELAY will the ENABLE input

signal, otherwise it is an automatic function at power down.

The reference voltage input is basically that voltage, at which the output current is zero.

ERROR AMP IN

input

ERROR AMP OUT

output

Error amplifier output pin. Open collector output.

OUTPUT A power

output

Voice Coil power output.

OUTPUT B power

output

Voice Coil power output.

SENSE AMP IN

A/B

signal input

Sense amplifier input pins. The sense resistor is connected across these pins.

SENSE AMP OUT

signal output

Output pin of sense amplifier.

LOGIC SUPPLY

FILTER

Capacitor connection to avoid false triggering

L6243DS

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