A8936CJT

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 ..................................... 0 °C to +70°C Junction Temperature, TJ .............. +150°C† Storage Temperature Range, TS ................................ -55°C to +150°C † 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 © 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 Rθ V REF + — RETRACT CONTROL PROTECT. CIRCUIT 8936 VOICE COIL MOTOR DRIVER ELECTRICAL CHARACTERISTICS at TA = +25°C, VCC = V DD = 5.0 V, VREF = VIN= 2.0 V, Load = 150 µH/3.5 Ω (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/ µs V µA 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 = +25°C, VCC = VDD = 5.0 V, VREF = VIN= 2.0 V, Load = 150 µH/3.5 Ω (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 µA 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 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 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