Providing control and drive of the voice-coil motor used for head

positioning in 5 V disk drive applications, the second-generation
A8932CLWA is a full-bridge driver that can be configured so that its
output current is a direct function of an externally applied control
voltage or current. This linear current control function is supplemented
by additional circuitry to protect the heads and the data disk during
system failure or normal system shutdown.

The two

±500 mA MOS driver outputs provide very low saturation

voltage and minimal power dissipation. Additional headroom is
achieved by the sense-FET structure eliminating the need for an exter-
nal current-sense resistor. Internal circuitry can be configured to
provide closed-loop velocity control of the actuator by utilizing the
generated back-EMF of the voice-coil motor. Thermal protection and
under-voltage lockout disables the system in a controlled sequence if a
fault condition occurs.

VOICE-COIL MOTOR DRIVER

FEATURES

I Class-B, 2

DS(on)

at 500 mA Output

I Lossless Current Sensing
I Zero Current-Loop Deadband
I High Transconductance Bandwidth
I User-Adjustable Transconductance Gain
I Digital Transconductance Gain Switch (4:1 Ratio)
I 5 Volt Monitor with Selectable UV Trip Point
I Retract Circuitry Functional to 0 Volts
I Sleep Mode Function
I Internal Back-EMF Velocity Loop Option
I Internal Thermal Shutdown Circuitry

Data Sheet

26300.2A

Always order by complete part number, e.g., A8932CLWA .

ABSOLUTE MAXIMUM RATINGS

Supply Voltages, V

and V

............ 6.0 V

Output Current, I

OUT

(peak) ...........

±600 mA

(continuous) ...........................

±500 mA

Analog Input Voltage Range,

.................................... -0.3 V to V

Logic Input Voltage Range,

............................... -0.3 V to +6.0 V

Package Power Dissipation,

......................................... See Graph

Operating Temperature Range,

..................................... 0

C to +70

Junction Temperature, T

............... +150

Storage Temperature Range,

................................ -55

C to +150

Fault conditions that produce excessive junction
temperature will activate device thermal shutdown
circuitry. These conditions can be tolerated, but
should be avoided.

Output current rating may be restricted to a value
determined by system concerns and factors.
These include: system duty cycle and timing,
ambient temperature, and use of any heatsinking
and/or forced cooling. For reliable operation the
specified maximum junction temperature should
not be exceeded.

RET SET

LOAD
SUPPLY

ACT

REFERENCE

H GAIN

PWR OFF

RET REF

GROUND

SWITCH

OUT

SIGNAL

SUPPLY

OUT

OUT P

SET

BEMF

FLT

SENS

LOAD

SENS FB

SGND

OUT

SGND

ACT

Dwg. PP-042B

RETRACT

FAULT

RESET

2 V

REF

PROTECT

CIRCUIT

PROTECT

CIRCUIT

8932-A

8932-A
VOICE-COIL MOTOR DRIVER

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

100

125

150

0.5

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

AMBIENT TEMPERATURE IN

°C

2.0

1.5

1.0

Dwg. GP-034

FREE AIR,

R = 66

°C/W

FUNCTIONAL BLOCK DIAGRAM

ERROR

AMP

POWER

AMP

POWER

CONTROL

LOGIC

CURRENT-SENSE
AMP

Dwg. FP-024D

SENSE +

SENSE

PROTECTION

CIRCUITRY

RETRACT

CONTROL

TSD

SIGNAL

SUPPLY

LOAD

SUPPLY

VOLTAGE-SENSE

AMP

2 V

REF.

ACT

REFERENCE

H GAIN

PWR OFF

FAULT

ACT

RESET

SWITCH

GROUND

BEMF

SET

FLT

RET SET

RET REF

OUT P

RETRACT

LOAD

OUT

SENS FB

OUT

SENS

SGND

OUT

REF.

8932-A

VOICE-COIL MOTOR DRIVER

www.allegromicro.com

ELECTRICAL CHARACTERISTICS at T

= +25

C, V

= V

= 5.0 V, V

REF

= V

= 2.0 V,

Load = 150

H/3.5

(unless otherwise noted).

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Error Amplifier

Input Offset Voltage

LOAD

= 0 mA

±50

Current Gain

H GAIN

3.5 V

7200

8000

8800

H GAIN

0.7 V

1800

2000

2200

Current Gain Linearity

L(adj)

OUT

= 5 mA to 500 mA, A

= A

±10

OUT

= 5 mA to 500 mA, A

= A

±10

Reference Voltage Range

REF

1.5

2.5

Voltage-Sense Amplifier

Voltage Gain

0.36

0.40

0.44

Output Offset Voltage

LOAD

= 0 mA

±25

Current-Sense Amplifier

Amplifier Error

x I

LOAD

/ (A

x V

SENSE

)) - 1

1.0

Input Offset Voltage

LOAD

= 0 mA, A

= A

±25

Output Drivers

Total On Resistance

DS(on)

LOAD

= 100 mA

2.0

2.5

(Source + Sink)

LOAD

= 500 mA

2.0

2.5

Retract Output Voltage Error

OUT(PN)

OUT(P)

- V

OUT(N)

- V

RETSET

±100

Full Power Bandwidth

-3 dB

1.0

kHz

Uncommitted Op Amp

Voltage Gain

Unity Gain Bandwidth

1.0

MHz

Max. Load Capacitance

LOAD

Slew Rate

4.2

µs

Output Voltage

SWITCH

0.7 V

2.5

3.5

OSW

SWITCH

3.5 V

2.5

3.5

Max. Output Current

±250

µA

Input Offset Voltage

±10

Continued next page...

Negative current is defined as coming out of (sourcing) the specified device terminal.

Typical Data is for design information only.

8932-A
VOICE-COIL MOTOR DRIVER

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

Miscellaneous

Supply Voltage

Operating

4.5

5.0

5.5

Operating

4.5

5.0

5.5

Under-Voltage Lockout Voltage

= V

3.9

4.2

4.35

Fault Logic Output

FAULT

RETRACT

3.5 V

500

RETRACT

0.7 V

4.5

FAULT

FLT

= 2.25 V

>20

µA

Power-On Reset

MPRESET

RETRACT

3.5 V

4.5

RETRACT

0.7 V, I

MPREST

= 1.5 mA

800

Total Supply Current

+ I

Outputs Balanced, No Load

Sleep Mode, PWR OFF = V

2.0

Logic Input Voltage

IN(0)

0.7

IN(1)

3.5

Thermal Shutdown Temperature

165

°C

Thermal Shutdown Hysteresis

°C

ELECTRICAL CHARACTERISTICS at T

= +25

C, V

= V

= 5.0 V, V

REF

= V

= 2.0 V,

Load = 150

H/3.5

(unless otherwise noted).

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Negative current is defined as coming out of (sourcing) the specified device terminal.

Typical Data is for design information only.

The products described here are manufactured under one or more

U.S. patents or U.S. patents pending.

Allegro MicroSystems, Inc. reserves the right to make, from time to

time, such departures from the detail specifications as may be required
to permit improvements in the performance, reliability, or
manufacturability of its products. Before placing an order, the user is
cautioned to verify that the information being relied upon is current.

Allegro products are not authorized for use as critical components

in life-support devices or systems without express written approval.

The information included herein is believed to be accurate and

reliable. However, Allegro MicroSystems, Inc. assumes no responsi-
bility for its use; nor for any infringement of patents or other rights of
third parties which may result from its use.

8932-A

VOICE-COIL MOTOR DRIVER

www.allegromicro.com

Term.

Terminal Name

Function

RET REF

The reference supply for setting the voltage across the load during retract.

FLT

Reservoir (energy storage) capacitor used to operate fault circuitry.

BEMF

Back-EMF voltage from spindle motor used to retract heads during loss of power.

GROUND

Circuit reference.

SET

Under-voltage trip point reference input. Set internally to 4.2 V but may be overridden by
external resistor divider. (Equation 4).

OUT P

Source driver used for retract; externally connected to OUT

OUT

Output of uncommitted operational amplifier.

SWITCH

Logic input for transmission gate; a high level connects OUT to OUT

Inverting input to uncommitted operational amplifier.

OUT

Transmission-gated output of uncommitted operational amplifier.

RETRACT

An active-low logic input that initiates the retract sequence.

FAULT

A logic low at this MOS output indicates a thermal shutdown, under-voltage fault, or retract
command.

RESET

(Power-On Reset) A logic low at this open-collector output may be used to reset the
system on under-voltage fault or power on.

SIGNAL SUPPLY

; low-current supply voltage in the range of 4.5 V to 5.5 V.

ACT

Input which controls the current in the load. Transconductance gain is set with an external
resistor in series with this input (Equation 1).

REFERENCE

REF

; reference input for all amplifiers; ac ground.

H GAIN

Logic input to switch the error amplifier transconductance gain: LOW = 2000,
HIGH = 8000.

PWR OFF

An active-high logic input that puts the device in a "sleep mode".
All fault circuitry remains active.

ACT

Input connection for feedback network which sets the error amplifier gain and bandwidth.

SGND

Power ground for the OUT

sink driver.

OUT

Power output. Sinks current when V

ACT

< V

REF

LOAD SUPPLY

; high-current supply voltage for the voice-coil motor.

OUT

Power output. Sinks current when V

ACT

> V

REF

SGND

Power ground for the OUT

sink driver.

SENS FB

Input connection for feedback network which sets the current-sense amplifier gain and
bandwidth. Also called gm SET.

LOAD

An output voltage proportional to the load voltage. Used in conjunction with closed-loop
velocity control.

SENS

Voltage output representing load current (Equation 2). Also called MONITOR.

RET SET

An external resistor divider to set the retract voltage across the load. Used in conjunction
with V

RET-REF

(Equation 3).

TERMINAL FUNCTIONS

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