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8936DATA SHEET INTERIM
March 16, 1993
VOICE change without notice) COIL MOTOR DRIVER (Subject to
8936
VOICE COIL MOTOR DRIVER
Data Sheet 26300.6
A8936CLW
RET REF V FLT V BEMF GROUND UV SET 1 2 3 4 5 28 R S WINDOW COMP. Q 27 26 25 24 23 RET SET V SENS VEL FLT V SENS FB SGND N OUTP
PROTECT CIRCUIT
R OUT P
OUT
EN VEL FLT
IN N VEL IN
RETRACT FAULT MP RESET
SIGNAL SUPPLY
ABSOLUTE
Supply Voltages, VCC and VDD ........... 6.0 V Output Current, IOUT (peak) .......... 600 mA (continuous) ........................... 500 mA Analog Input Voltage Range, VIN ................................... -0.3 V to VCC Logic Input Voltage Range, VIN ............................... -0.3 V to +6.0 V Package Power Dissipation, PD ........................................ See Graph Operating Temperature Range, TA ..................................... 0C to +70C Junction Temperature, TJ .............. +150C Storage Temperature Range, TS ................................ -55C to +150C
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.
T C UY DL ON RO PE DC EN UE IN ER TF NE OR CR IS O DF --
V REF 6 7 8
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.
+ -
VREF
VDD
22
LOAD SUPPLY OUT N
21 20
9
SGND P ACT FB
10
19 18 17 16
11
PWR OFF H GAIN
12
PROTECT CIRCUIT
13
14
V CC
+ -
REFERENCE ACT
15
FEATURES
s s s s s s s s s s s
Dwg. PP-046A
MAXIMUM
RATINGS
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
Always order by complete part number: Part Number Package A8936CJT A8936CLW
64-Lead Thin Quad Flatpack 28-Lead SOIC
A
TM
MicroSystems, Inc.
8936
VOICE COIL MOTOR DRIVER
FUNCTIONAL
= 'LW' WIDE-BODY SOIC = 'JT' THIN QUAD FLATPACK SIGNAL SUPPLY
14 53
BLOCK
LOAD SUPPLY VDD
DIAGRAM
ACT FB 19 1 ERROR - AMP
I SENSE +
ACT 15 55 REFERENCE 16 58 H GAIN 17 60
+
2V POWER CONTROL LOGIC
+ -
POWER AMP
PWR OFF 18 62
I SENSE -
CURRENT-SENSE AMP
-
V REF
+
WINDOW COMP.
46 10
TSD FAULT 12 50 MP RESET 13 51 PROTECTION CIRCUITRY
33 5 28 3 27 2 23 28
RETRACT CONTROL
25 1 47 11 34 6 19 26
Q Q
S R
30 4
RETRACT
UVSET
VBEMF
V FLT
RET SET
RET REF
R OUT P
VEL FLT
GROUND
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
2.0
+ --
V CC PROTECT. CIRCUIT
1.5
1.0
V
DD
V REF
WINDOW
0.5
COMP.
S
R
0
Q
25
50 75 100 125 AMBIENT TEMPERATURE IN C
150
Dwg. GP-034
Dwg. PP-052-1
A
TM
MicroSystems, Inc.
115 Northeast Cutoff, Box 15036 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright (c) 1992, 1993, Allegro MicroSystems, Inc.
-
45 9 2 20 13 23 4 21 15 24 16 25 21 27
V CC
V REF
+
35 7
22
8
OUT IN N SGND P OUT P OUT N SGND N V SENS FB V SENS
VEL IN EN VEL FLT
V REF
36 8
Dwg. FP-030A
A8936CJT
/W R, C AI 66 EE = FR JA R
V REF
+
--
RETRACT CONTROL PROTECT. CIRCUIT
8936
VOICE COIL MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at TA = +25C, VCC = V DD = 5.0 V, VREF = VIN= 2.0 V, Load = 150 H/3.5 (unless otherwise noted).
Characteristic Error Amplifier Input Offset Voltage Current Gain Current Gain Linearity Reference Voltage Range Current-Sense Amplifier Voltage Gain Input Offset Voltage Output Drivers Output Saturation Voltage (Source + Sink) Retract Output Saturation Voltage Output Current Full Power Bandwidth Window Comparator Lower Trip Point Upper Trip Point Uncommitted Op Amp Voltage Gain Unity Gain Bandwidth Max. Load Capacitance Slew Rate Output Voltage Max. Output Current Input Offset Voltage AVS BW CLOAD SR VO IO V IO VIO = 100 mV -- -- 40 -- 2.5 -- -- 91 1.0 -- 4.2 -- 250 -- -- -- -- -- 3.5 -- 10 dB MHz pF V/s V A mV VEL IN VEL IN 1.12 2.47 1.25 2.75 1.38 3.03 V V V DS(SAT) ILOAD = 100 mA ILOAD = 500 mA V DS(SAT) IO BW IOUT 150 mA Pulse Test, 600 mA Limited -3 dB -- -- -- -- 1.0 0.25 1.5 -- -- -- -- -- 1.0 500 -- V V V mA kHz A VD ViO Rs = Rgm ILOAD = 0 mA, A i = AiL -- -- 1.0 -- -- 25 -- mV V IO A iH A iL E L(adj) VREF ILOAD = 0 mA H GAIN 3.5 V H GAIN 0.7 V IOUT = 5 mA to 500 mA, Ai = A iL IOUT = 5 mA to 500 mA, Ai = A iH -- 7200 1800 -- -- 1.5 -- 8000 2000 -- -- -- 50 8800 2200 10 10 2.5 mV -- -- % % V Symbol Test Conditions Min. Limits Typ. Max. Units
Continued next page ... Negative current is defined as coming out of (sourcing) the specified device terminal. Typical Data is for design information only.
8936
VOICE COIL MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at TA = +25C, VCC = VDD = 5.0 V, VREF = VIN= 2.0 V, Load = 150 H/3.5 (unless otherwise noted).
Characteristic Miscellaneous Under-Voltage Lockout Voltage Fault Logic Output VCC V FAULT V CC = V DD V RETRACT 3.5 V V RETRACT 0.7 V IFAULT Power-On Reset V MPRESET V FLT = 2.25 V V RETRACT 3.5 V V RETRACT 0.7 V, IMPRESET = 1.5 mA Total Supply Current ICC + IDD Outputs Balanced, No Load Sleep Mode, PWR OFF = VCC Logic Input Voltage V IN(0) V IN(1) Thermal Shutdown Temperature Thermal Shutdown Hysteresis TJ T J 3.9 -- 4.5 20 4.5 -- -- -- -- 3.5 -- -- 4.2 -- -- -- -- -- -- -- -- -- 165 20 4.35 500 -- -- -- 800 10 2.0 0.7 -- -- -- V mV V A V mV mA mA V V C C Symbol Test Conditions Min. Limits Typ. Max. Units
Negative current is defined as coming out of (sourcing) the specified device terminal. Typical Data is for design information only.
A
TM
MicroSystems, Inc.
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8936
VOICE COIL MOTOR DRIVER
TERMINAL
"JT" Term."LW" Term. Term. Name 25 27 28 30 33 1 2 3 4 5 RET REF VFLT VBEMF GROUND UVSET R OUT P OUT EN VEL FLT INN VELIN RETRACT FAULT MPRESET Function
FUNCTIONS
The reference supply for setting the voltage across the load during retract. Reservoir (energy storage) capacitor used to operate fault circuitry. Back-EMF voltage from spindle motor used to retract heads during loss of power. Circuit reference. Under-voltage trip point reference input. Set internally to 4.3 V but may be over-ridden by external resistor divider. (Equation 4). Source driver used for retract; externally connected to OUTP. Output of uncommitted operational amplifier. Logic input for over-velocity fault latch. Inverting input to uncommitted operational amplifier. Analog voltage input corresponding to motor speed. An active-low logic input that initiates the retract sequence. A logic low at this MOS output indicates a thermal shutdown, under-voltage fault, or retract command. (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.
34 35 36 45 46 47 50 51
6 7 8 9 10 11 12 13
53 55
14 15
SIGNAL SUPPLY VCC ; 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).
58 60 62 1 2 4 8 13 15 16
16 17 18 19 20 21 22 23 24 25
REFERENCE VREF; reference input for all amplifiers; ac ground. H GAIN PWR OFF ACTFB SGNDP OUTN Logic input to switch the error amplifier transconductance gain: LOW = 2100, HIGH = 8400. An active-high logic input that puts the device in a "sleep mode". All fault circuitry remains active. Input connection for feedback network which sets the error amplifier gain and bandwidth. Power ground for the OUTP sink driver. Power output. Sinks current when VACT < VREF.
LOAD SUPPLY VDD ; high-current supply voltage for the voice-coil motor. OUTP SGNDN V SENS FB VEL FLT V SENS RET SET Power output. Sinks current when VACT > VREF. Power ground for the OUTN sink driver. Input connection for feedback network which sets the current-sense amplifier gain and bandwidth. Also called gm SET. An active-low logic output indicating an over-velocity fault. Voltage output representing load current (Equation 2). Also called MONITOR. An external resistor divider to set the retract voltage across the load. Used in conjunction with VRET-REF (Equation 3).
19 21 23
26 27 28
8936
VOICE COIL MOTOR DRIVER
DEVICE
Current Amplifier. The A8936CJT and A8936CLW voice coil motor drivers feature a wide transconductance bandwidth and no measurable crossover distortion. The transconductance gain is user selectable: gm = Ai Rgm
DESCRIPTION
If the velocity control scheme is implemented, the head can be retracted under the full control of INPUT in conjunction with OUTSW back-EMF voltage if no fault condition exists. If a fault condition were to occur however, the retract velocity would be controlled by applying a constant user-defined voltage across the load: V RET-SET = 2 R8 1000 + R7 + R8
(Equation 1) (Equation 3)
where Ai is either 2000 (H GAIN = Low) or 8000 (H GAIN = High) The error amplifier's bandwidth and load compensation zero are set utilizing external resistor and capacitor feedback components around the amplifier. The actuator main loop compensation can be set by applying a square wave and adjusting R Z and CZ for optimum response. Current and Voltage Sensing. The load current is sensed internally. Two auxiliary amplifiers are also included to allow various control functions to be implemented. The first of these amplifiers provides a voltage output that is proportional to the load current: V SENS = RS ILOAD AiL
where R7 + R8 >> 1000 . When the sequence is operated, the output voltage is forced to approximately VRET-SET to retract the heads, and then a fault command ("brake") is sent to the spindlemotor driver. The user determines the total time for the retract sequence, before the spindle brake is enabled, by the choice of an external resistor and capacitor at the FAULT output. Power for the retract function is provided by the rectified back EMF of the spindle motor by way of the VBEMF terminal. The A8936CJT/CLW will perform the retract function under low supply conditions (nominally down to 2 V). Operation down to almost 0 V requires an energy-storage capacitor at the VFLT terminal. Protective Features. The A8936CJT/CLW has a number of protective features incorporated into the design. Under-voltage lockout provides system protection in the event of reduced primary supply voltages. The undervoltage trip point is internally set at approximately 4.3 V. It can be user-defined with an external resistor voltage divider: UVTRIP = 2 (R5 + R 6) R6
(Equation 2)
The second auxiliary amplifier may be used in conjunction with the first to provide a closed-loop velocity control system for the actuator arm during a controlled retract for head parking. Under- & Over-Velocity Fault. For a constant load, motor current (ILOAD) and therefore VSENS are proportional to motor velocity. VSENS is amplified by the uncommitted amplifier and compared against the internal 2 V reference and used to indicate a velocity fault if the voltage is greater than a nominal 0.75 V from the 2 V reference. EN VEL FLT may be tied to the FAULT terminal to reset the velocity fault after a tripout. Retract and Brake. A retract-brake sequence is initiated on receiving a fault indication from the internal thermal shutdown (TSD), under-voltage lockout (UVLO), the under- or over-velocity fault, or an externally applied logic High at the RETRACT input.
(Equation 4)
where R5 + R6 << 200 k. Thermal shutdown circuitry is included to protect the device from excessive junction temperature. It is only intended to protect the chip from catastrophic failures due to excessive junction temperature.
A
TM
MicroSystems, Inc.
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8936
VOICE COIL MOTOR DRIVER
TEST CIRCUIT AND TYPICAL APPLICATION
+5 V RZ CZ V CC
I SENSE +
V DD
V REF
- -
V IN
Rgm
-
VREF = 2 V H GAIN
ERROR AMP
+
2V POWER CONTROL LOGIC
+ -
POWER AMP
PWR OFF
I SENSE -
CURRENT-SENSE AMP
R FAULT
200 k
TSD Q Q
V REF
PROTECTION CIRCUITRY
RETRACT CONTROL
S R
WINDOW COMP.
R VCC
RETRACT
R R6
7
R8
BACK EMF FROM SPINDLE MOTOR
VDD
DIODE FOR RETRACT FUNCTION OTHERWISE SHORT TO SUPPLY
Dwg. EP-043A
VEL FLT
5
+
C1 R1 VOICE COIL MOTOR RS V SENS
- +
V REF
8936
VOICE COIL MOTOR DRIVER
A8936CJT
Dimensions in Inches (Based on 1 mm = 0.03937")
48
33
0.0039 0.0024
49 32
0.005 0.017 0.472
BSC
EJECTOR MARK
0.394
BSC
INDEX MARK
0.0197
BSC
64
17
0.018 0.030
1 16
0.0035 0.0079 0.050 0.065
0.394
BSC
0.472
BSC
Dwg. MA-004 in
NOTES: 1. This device is similar to JEDEC registration MO-136BJ except for certain tolerances. Contact factory for detailed information. 2. Lead spacing tolerance is non-cumulative. 3. Exact body and lead configuration at vendor's option within limits shown. 4. The top package body size may be smaller than the bottom package body size by as much as 0.006". Body dimensions include mold mismatch but do not include mold protrusion.
A
TM
MicroSystems, Inc.
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8936
VOICE COIL MOTOR DRIVER
A8936CJT
Dimensions in Millimeters
48
33
0.10 0.06
49 32
0.14 0.27 12.0
BSC
EJECTOR MARK
10.0
BSC
INDEX MARK
0.50
BSC
64
17
0.30 0.75
1 16
0.09 0.20 1.29 1.65
10.0
BSC
12.0
BSC
Dwg. MA-004 mm
NOTES: 1. This device is similar to JEDEC registration MO-136BJ except for certain tolerances. Contact factory for detailed information. 2. Lead spacing tolerance is non-cumulative. 3. Exact body and lead configuration at vendor's option within limits shown. 4. The top package body size may be smaller than the bottom package body size by as much as 0.15 mm. Body dimensions include mold mismatch but do not include mold protrusion.
8936
VOICE COIL MOTOR DRIVER
A8936CLW
DIMENSIONS IN INCHES (Based on 1 mm = 0.03937")
28 15 0.0125 0.0091
0.2992 0.2914
0.491 0.394 0.050 0.016
0.020 0.013
1
2
3 0.7125 0.6969
0.050 BSC
0 TO 8
0.0926 0.1043 0.0040 MIN.
Dwg. MA-008-28 in
DIMENSIONS
28
IN
15
MILLIMETERS
0.32 0.23
7.60 7.40
10.65 10.00 1.27 0.40
0.51 0.33
1
2
3 18.10 17.70
1.27 BSC
0 TO 8
2.65 2.35 0.010 MIN.
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 design of its products. Components made under military approvals will be in accordance with the approval requirements. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
Dwg. MA-008-28 mm
NOTES: 1. Lead spacing tolerance is non-cumulative. 2. Exact body and lead configuration at vendor's option within limits shown.
A
TM
MicroSystems, Inc.
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

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