Allegro A8936CLW, A8936CJT Datasheet

8936

INTERIM DATA SHEET

VOICE COIL MOTOR DRIVER

(Subject to change without notice)
March 16, 1993

8936

Data Sheet

26300.6

VOICE COIL MOTOR DRIVER

A8936CLW

1

RET REF

V

2

V

BEMF

GROUND

UV

R

OUT P

OUT

EN VEL FLT

IN

VEL

RETRACT

FAULT

MP

RESET

SIGNAL

SUPPLY

FLT

PROTECT

CIRCUIT

3

4

5

SET

6

V

+

PROTECT

CIRCUIT

V

CC

REF

–

7

8

9

N

10

IN

11

12

13

14 15

WINDOW

COMP.

V

REF

R

Q

S

ABSOLUTE MAXIMUM RATINGS

Supply Voltages, VCC and VDD........... 6.0 V

Output Current, I

(continuous) ........................... ±500 mA

Analog Input Voltage Range,

V

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

IN

Logic Input Voltage Range,

V

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

IN

Package Power Dissipation,

P

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

D

(peak) .......... ±600 mA

OUT

RET SET

28

27

V

SENS

VEL FLT

26

V

25

SENS FB

24

SGND

N

OUT

23

P

LOAD

22

V

DD

SUPPLY

21

OUT

N

SGND

20

P

ACT

19

FB

18

PWR OFF

H GAIN

17

16

REFERENCE

+

–

ACT

Dwg. PP-046A

CC

Providing control and drive of the voice coil motor used for head
positioning in 5 V disk drive applications, the A8936C— is a full-bridge
driver which 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. An under- or over-velocity sense disables the
system in a controlled sequence if a fault condition occurs.

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
external current-sense resistor. Thermal protection and under-voltage
lockout disables the system in a controlled sequence if a fault condi­tion occurs.

FEATURES

■ Over-Velocity Fault Function

■ Lossless Current Sensing

■ Zero Deadband

■ High Transconductance Bandwidth

■ User-Adjustable Transconductance Gain

■ Digital Transconductance Gain Switch (4:1 Ratio)

■ 5 Volt Monitor with Selectable UV Trip Point

■ Retract Circuitry Functional to 0 Volts

■ Chip Enable/Sleep Mode Function

■ 1 V at 500 mA Output Saturation Voltage

■ Internal Thermal Shutdown Circuitry

Operating Temperature Range,

T

.....................................0°C to +70°C

A

Junction Temperature, T

.............. +150°C

J

†

Storage Temperature Range,

T

................................-55°C to +150°C

S

DISCONTINUED PRODUCT

† 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

— FOR REFERENCE ONLY

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.

Always order by complete part number:

Part Number Package
A8936CJT 64-Lead Thin Quad Flatpack
A8936CLW 28-Lead SOIC

A

TM

TM

MicroSystems, Inc.

8936

VOICE COIL MOTOR DRIVER

FUNCTIONAL BLOCK DIAGRAM

= 'LW' WIDE-BODY SOIC
= 'JT' THIN QUAD FLATPACK

19

FB

1

15

55

16

58

60

17

18

62

12

50

13

51

ACT

ACT

REFERENCE

H GAIN

PWR OFF

FAULT

MP

RESET

SIGNAL

SUPPLY

14 22

V

CC

I

SENSE +

ERROR

AMP

–

2 V

+

–

+

POWER

CONTROL

LOGIC

TSD

PROTECTION

CIRCUITRY

33

28 27 23 25 47 34

53 2 281 611 4

SET

BEMF

UV

V

V

FLT

RETRACT
CONTROL

RET REF

RET SET

POWER

AMP

I

SENSE –

RETRACT

LOAD

SUPPLY

853

V

DD

19
26

OUT P

R

V

REF

CURRENT-SENSE
AMP

V

REF

S

Q

R

Q

VEL FLT

+

–

–

+

WINDOW

COMP.

30

GROUND

35

45

2

13

4

15

16

21

46

V

REF

36

7

OUT

9

IN

20

SGND

23

OUT

21

OUT

24

SGND

25

V

27

V

10

VEL

8

EN VEL FLT

Dwg. FP-030A

N

P

P

N

N

SENS FB

SENS

IN

2.0

1.5

FREE AIR,

R = 66°C/W

θJA

1.0

0.5

0

25

ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS

A

50 75 100 125 150

AMBIENT TEMPERATURE IN °C

Dwg. GP-034

TM

TM

MicroSystems, Inc.

115 Northeast Cutoff, Box 15036
115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 [phone]
Worcester, Massachusetts 01615-0036 [phone]

Copyright © 1992, 1993, Allegro MicroSystems, Inc.

A8936CJT

V

PROTECT.

CIRCUIT

CC

PROTECT.

CIRCUIT

V

REF

+ —

Dwg. PP-052-1

+

—

V

DD

V

REF

WINDOW

COMP.

S R
Q

RETRACT
CONTROL

8936

VOICE COIL MOTOR DRIVER

ELECTRICAL CHARACTERISTICS at T

= +25°C, VCC = VDD = 5.0 V, V

A

= VIN= 2.0 V,

REF

Load = 150 µH/3.5 Ω (unless otherwise noted).

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units
Error Amplifier

Input Offset Voltage V
Current Gain A

Current Gain Linearity E

Reference Voltage Range V

IO

iH

A

iL

L(adj)

REF

Current-Sense Amplifier

Voltage Gain A
Input Offset Voltage V

VD

iO

Output Drivers

Output Saturation Voltage V

DS(SAT)

(Source + Sink)

Retract Output Saturation Voltage V
Output Current I

DS(SAT)

O

Full Power Bandwidth BW -3 dB 1.0 —— kHz

Window Comparator

Lower Trip Point VEL
Upper Trip Point VEL

IN

IN

Uncommitted Op Amp

Voltage Gain A

VS

Unity Gain Bandwidth BW — 1.0 — MHz
Max. Load Capacitance C

LOAD

Slew Rate SR — 4.2 — V/µs
Output Voltage V
Max. Output Current I
Input Offset Voltage V

O

O

IO

I

= 0 mA ——50 mV

LOAD

H GAIN ≥ 3.5 V 7200 8000 8800 —
H GAIN ≤ 0.7 V 1800 2000 2200 —
I

= 5 mA to 500 mA, Ai = A

OUT

= 5 mA to 500 mA, Ai = A

I

OUT

iL
iH

——±10 %
——±10 %

1.5 — 2.5 V

Rs = R

gm

I

= 0 mA, Ai = A

LOAD

I

= 100 mA — 0.25 — V

LOAD

I

= 500 mA — 1.5 — V

LOAD

I

≤ 150 mA ——1.0 V

OUT

iL

— 1.0 ——
——±25 mV

Pulse Test, ±600 mA Limited ——±500 mA

1.12 1.25 1.38 V

2.47 2.75 3.03 V

— 91 — dB

40 —— pF

VIO = 100 mV 2.5 — 3.5 V

— ±250 — µA
——±10 mV

Negative current is defined as coming out of (sourcing) the specified device terminal.
Typical Data is for design information only.

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