8936

8936 ALLEGRO

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— FOR REFERENCE ONL Y TM MicroSystems, Inc. TM A 8936 VOICE COIL MOTOR DRIVER 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 condi- tion occurs.

FEATURES

I Over-Velocity Fault Function I Lossless Current Sensing I Zero 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 Chip Enable/Sleep Mode Function I 1 V at 500 mA Output Saturation Voltage I Internal Thermal Shutdown Circuitry Data Sheet 26300.6 INTERIM DATA SHEET (Subject to change without notice) March 16, 1993 A8936CLW ABSOLUTE MAXIMUM RATINGS Analog Input Voltage Range, Logic Input Voltage Range, Package Power Dissipation, Operating Temperature Range, Storage Temperature Range, † 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. Q 14 15 RET SET LOAD SUPPLY ACT REFERENCE H GAIN PWR OFF RET REF GROUND EN VEL FLT OUT SIGNAL SUPPLY VEL IN INN R OUT P UV SET V BEMF V FLT CCV V SENS VEL FLT V SENS FB SGND N OUT P OUT N VDD SGND P ACT FB Dwg. PP-046A RETRACT FAULT MP RESET WINDOW COMP. PROTECT CIRCUIT PROTECT CIRCUIT V REF VREF R S Always order by complete part number: Part Number Package A8936CJT 64-Lead Thin Quad Flatpack A8936CLW 28-Lead SOIC

MicroSystems, Inc. TM A

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000 FUNCTIONAL BLOCK DIAGRAM V REF –ACT REFERENCE H GAIN PWR OFF FAULT EN VEL FLT ERROR AMP POWER AMP ACT FB V SENS FB POWER CONTROL LOGIC VBEMF UV SET OUT P OUT N V SENS CURRENT-SENSE AMP REF Dwg. FP-030A V FLT RET SET RET REF R OUT P MP RESET SENSE + I SENSE – I 2 V PROTECTION CIRCUITRY RETRACT CONTROL TSD SIGNAL SUPPLY LOAD SUPPLY SGND P SGND N GROUND VDDV CC 53 2 2 8 1 6 11 4 14 22 RETRACT VEL IN10 VEL FLT S R Q Q INN9 OUT7 WINDOW COMP. V = 'JT' THIN QUAD FLATPACK = 'LW' WIDE-BODY SOIC 33 28 27 23 25 47 34 19 30

853 V REF

Dwg. PP-052-1 WINDOW COMP. S R Q RETRACT CONTROL PROTECT. CIRCUIT PROTECT. CIRCUIT + — CCV V DD REFV REFV 50 75 100 125 150 0.5 ALLOWABLE PACKAGE POWER DISSIPATION IN WATTSAMBIENT TEMPERATURE IN °C 2.0 1.5 1.0 Dwg. GP-034 FREE AIR,R = 66 °C/W θJA Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1992, 1993, Allegro MicroSystems, Inc.

ELECTRICAL CHARACTERISTICS at TA = +25°C, VCC = VDD = 5.0 V, VREF = VIN= 2.0 V, Load = 150 µH/3.5 Ω (unless otherwise noted). (Source + Sink) Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units Error Amplifier Input Offset Voltage V IO ILOAD = 0 mA —— 50 mV Current Gain A iH H GAIN ≥ 3.5 V 7200 8000 8800 — A iL H GAIN ≤ 0.7 V 1800 2000 2200 — Current Gain Linearity E L(adj) IOUT = 5 mA to 500 mA, Ai = AiL —— ±10 % IOUT = 5 mA to 500 mA, Ai = AiH —— ±10 % Reference Voltage Range V REF 1.5 — 2.5 V Current-Sense Amplifier Voltage Gain A VD R s = Rgm — 1.0 —— Input Offset Voltage V iO ILOAD = 0 mA, Ai = AiL —— ±25 mV Output Drivers Output Saturation Voltage V DS(SAT) ILOAD = 100 mA — 0.25 — V ILOAD = 500 mA — 1.5 — V Retract Output Saturation Voltage V DS(SAT) IOUT ≤ 150 mA —— 1.0 V Output Current I O Pulse Test, ±600 mA Limited —— ±500 mA Full Power Bandwidth BW -3 dB 1.0 —— kHz Window Comparator Lower Trip Point VEL IN 1.12 1.25 1.38 V Upper Trip Point VEL IN 2.47 2.75 3.03 V Uncommitted Op Amp Voltage Gain A VS — 91 — dB Unity Gain Bandwidth BW — 1.0 — MHz Max. Load Capacitance C LOAD 40 —— pF Slew Rate SR — 4.2 — V/µs Output Voltage V O VIO = 100 mV 2.5 — 3.5 V Max. Output Current I O — ±250 — µA Input Offset Voltage V IO —— ±10 mV Continued next page … Negative current is defined as coming out of (sourcing) the specified device terminal. Typical Data is for design information only.

MicroSystems, Inc. TM A Worcester, Massachusetts 01615-0036 (508) 853-5000 Miscellaneous Under-Voltage Lockout Voltage V CC V CC = VDD 3.9 4.2 4.35 V Fault Logic Output V FAULT V RETRACT ≥ 3.5 V —— 500 mV V RETRACT ≤ 0.7 V 4.5 —— V IFAULT V FLT = 2.25 V 20 —— µA Power-On Reset V MPRESET V RETRACT ≥ 3.5 V 4.5 —— V V RETRACT ≤ 0.7 V, IMPRESET = 1.5 mA —— 800 mV Total Supply Current I CC + IDD Outputs Balanced, No Load —— 10 mA Sleep Mode, PWR OFF = VCC —— 2.0 mA Logic Input Voltage V IN(0) —— 0.7 V V IN(1) 3.5 —— V Thermal Shutdown Temperature T J — 165 — °C Thermal Shutdown Hysteresis ∆TJ — 20 — °C ELECTRICAL CHARACTERISTICS at TA = +25°C, VCC = VDD = 5.0 V, VREF = VIN= 2.0 V, Load = 150 µH/3.5 Ω (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.

"JT" Term."LW" Term. Term. Name Function 25 1 RET REF The reference supply for setting the voltage across the load during retract. 27 2 V FLT Reservoir (energy storage) capacitor used to operate fault circuitry. 28 3 V BEMF Back-EMF voltage from spindle motor used to retract heads during loss of power. 30 4 GROUND Circuit reference. 33 5 UV SET Under-voltage trip point reference input. Set internally to 4.3 V but may be over-ridden by external resistor divider. (Equation 4). 34 6 R OUT P Source driver used for retract; externally connected to OUTP. 35 7 OUT Output of uncommitted operational amplifier. 36 8 EN VEL FLT Logic input for over-velocity fault latch. 45 9 IN N Inverting input to uncommitted operational amplifier. 46 10 VEL IN Analog voltage input corresponding to motor speed. 47 11 RETRACT An active-low logic input that initiates the retract sequence. 50 12 FAULT A logic low at this MOS output indicates a thermal shutdown, under-voltage fault, or retract command. 51 13 MP 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. 53 14 SIGNAL SUPPLY VCC ; low-current supply voltage in the range of 4.5 V to 5.5 V. 55 15 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 16 REFERENCE V REF ; reference input for all amplifiers; ac ground. 60 17 H GAIN Logic input to switch the error amplifier transconductance gain: LOW = 2100, HIGH = 8400. 62 18 PWR OFF An active-high logic input that puts the device in a “sleep mode”. All fault circuitry remains active. 1 19 ACT FB Input connection for feedback network which sets the error amplifier gain and bandwidth. 2 20 SGND P Power ground for the OUTP sink driver. 4 21 OUT N Power output. Sinks current when VACT < VREF . 8 22 LOAD SUPPLY V DD ; high-current supply voltage for the voice-coil motor. 13 23 OUT P Power output. Sinks current when VACT > VREF . 15 24 SGND N Power ground for the OUTN sink driver. 16 25 V SENS FB Input connection for feedback network which sets the current-sense amplifier gain and bandwidth. Also called gm SET. 19 26 VEL FLT An active-low logic output indicating an over-velocity fault. 21 27 V SENS Voltage output representing load current (Equation 2). Also called MONITOR. 23 28 RET SET An external resistor divider to set the retract voltage across the load. Used in conjunction with VRET-REF (Equation 3). TERMINAL FUNCTIONS

MicroSystems, Inc. TM A Worcester, Massachusetts 01615-0036 (508) 853-5000 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: (Equation 1) where Ai is either 2000 (H GAIN = Low) or 8000 (H GAIN = High) The error amplifier’s bandwidth and load compensa- tion 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 imple- mented. The first of these amplifiers provides a voltage output that is proportional to the load current: (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 (I LOAD ) and therefore VSENS are proportional to motor velocity. VSENS is amplified by the uncommitted amplifier and compared against the internal 2 V refer- ence 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. If the velocity control scheme is implemented, the head can be retracted under the full control of INPUT in conjunction with OUT SW back-EMF voltage if no fault condition exists. If a fault condition were to occur how- ever, the retract velocity would be controlled by applying a constant user-defined voltage across the load: (Equation 3) where R7 + R8 >> 1000 Ω . 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 spindle- motor 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 V BEMF 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 V FLT 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 under- voltage trip point is internally set at approximately 4.3 V. It can be user-defined with an external resistor voltage divider: (Equation 4) where R5 + R6 << 200 kΩ . 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. DEVICE DESCRIPTION A i R gm gm = R S ILOAD AiL V SENS = V RET-SET = 2 R8 1000 + R7 + R8 2 (R5 + R6) R 6 UV TRIP =

TEST CIRCUIT AND TYPICAL APPLICATION ERROR AMP POWER AMP POWER CONTROL LOGIC SENSE + I SENSE – I 2 V PROTECTION CIRCUITRY RETRACT CONTROL TSD V DDV CC S R Q Q +5 V R Z H GAIN PWR OFF R gm C Z R 6 R R VIN VDD DIODE FOR RETRACT FUNCTION OTHERWISE SHORT TO SUPPLYRETRACT VCC R BACK EMF FROM SPINDLE MOTOR VEL FLT WINDOW COMP. CURRENT-SENSE AMP VOICE COIL MOTOR R S V SENS Dwg. EP-043A V = 2 VREF V REF V REF R ≥ 200 kΩFAULT REFV

MicroSystems, Inc. TM A Worcester, Massachusetts 01615-0036 (508) 853-5000 A8936CJT Dimensions in Inches (Based on 1 mm = 0.03937”) 3348 Dwg. MA-004 in 0.0197 BSC 0.005 0.017 0.0035 0.0079 0.050 0.065 INDEX MARK 0.018 0.030 0.0039 ±0.0024 0.394 BSC 0.472 BSC 0.472 BSC 0.394 BSC 49 32 EJECTOR MARK 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.

Dwg. MA-004 mm 0.50 BSC 0.14 0.27 0.09 0.20 1.29 1.65 INDEX MARK 0.30 0.75 0.10 ±0.06 EJECTOR MARK 10.0 BSC 12.0 BSC 12.0 BSC 10.0 BSC 49 32 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.

MicroSystems, Inc. TM A Worcester, Massachusetts 01615-0036 (508) 853-5000 A8936CLW DIMENSIONS IN INCHES (Based on 1 mm = 0.03937") 0.2992 0.2914 0° TO 8° 1 2 3 0.7125 0.6969 0.020 0.013 0.0040 MIN. Dwg. MA-008-28 in 0.050 BSC 28 15 0.491 0.394 0.0125 0.0091 0.050 0.016 0.0926 0.1043 NOTES: 1. Lead spacing tolerance is non-cumulative. 2. Exact body and lead configuration at vendor’s option within limits shown. DIMENSIONS IN MILLIMETERS 0° TO 8° 2 3 7.60 7.40 18.10 17.70 10.65 10.00 0.51 0.33 0.010 MIN. 0.32 0.23 1.27 0.40 Dwg. MA-008-28 mm 1.27 BSC 2.65 2.35 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.