L6256 datasheet(2/28 Pages) STMICROELECTRONICS

2 / 28 page

constant torque. This is a very high power dissi-

pation mode, meant only for momentary opera-

tion in unusual circumstances.

Spindown during a power failure uses the back

EMF voltage generated by the spindle motor to

provide power to the VCM amplifier. The Spindle

motor coasts during the Brake Delay time to allow

time to park the head actuator. The park circuit is

a constant voltage circuit settable externally.

After the head is parked, braking commences.

The brake operates by shorting all 3 windings.

The spindle output stages stay on as long as is

required to bring the motor to a complete stop,

even if no power is applied to the part.

A Power On Reset (POR) function provides pulse

stretching for the bidirectional POR\ bus, to en-

sure that the processor and clocks are at running

speed before allowing them to function.

5 volt and 12 volt pins are used directly for the un-

dervoltage detect circuit.

This allows direct use internally of both supplies.

Voltage monitor margining is supported.

An external 3.3V linear regulator is provided and

tied into the POR circuit.

ABSOLUTE MAXIMUM RATINGS

Symbol

Parameter

Value

Unit

VPWR

Normal Operating Voltage

VPVR

Inductive Clamp Voltage @ 2mH, 1.6A, 3% Duty Cycle

<20

V (1)

Vdd

VCC

6.4

I_VCM, Aout

-2 to VPWR +2V

Logic I/O, SH_Out, PWM_DC

-0.3 to VCC +0.3

All other pins

-0.3 to VPWR +0.3V

Tstg

Storage Ambient Temperature

-65 to +150

°C

ESD capability

±2kV

(1) Limited by chip clamp voltage.

44 43

24 25

GND

R_SLEW

POR_RC

nPOR

BEMF_DET

PWM_IN

SCLK

SDIO

VCC

BYPASSC

5V_GND

GND

SH_OUT

FF_COMP

PWM_DC

VDD

REF_IN

H_VPWR

DAC

IO_VC

A_IN

GND

D97IN572

PIN CONNECTION

OPERATING CONDITIONS

VCC = 4.5 to 5.5V

Vdd = 10.8 to 13.2V

0°C < Tamb < 70°C.

DESCRIPTION (Continued)

L6256

2/28

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