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8980 SUPERSERVOTM SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
8980
TM
The A8980CJT provides complete drive, management, and control of the voice-coil and spindle motor power actuation subsystems used in hard disk drives. Extensive programmable control features and system diagnostics are provided via a serial interface under the direction of an external microcontroller. The large-scale integration and use of advanced DABiCTM (digital/analog-BiCMOS) merged technologies results in minimum power dissipation, minimum operating voltage requirements, and minimum external components. The spindle drive function incorporates a three-phase MOS power driver and a back-EMF sensing motor commutation scheme. Internal logic and analog circuitry provide complete start-up and C-assisted run modes without the need for snubbers or other external components. Additional headroom is achieved by a proprietary circuit, which eliminates the need for an external current-sense resistor. Intrinsic ground clamp and flyback diodes are also provided.
Data Sheet 26310
SUPERSERVO SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
C TAP
MULTIPLEXER
BACK-EMF and COMMUTATION LOGIC
8
SPIN-DEMAND
12
SERVO-DEMAND
ABSOLUTE MAXIMUM RATINGS
at TA = +25C
Load Supply Voltage, VCC(PWR) .......... 7.0 V Spindle Output Current, IOUT(S) ......... 1.6 A Voice-Coil Output Current, IOUT(S) .... 0.9 A Output Current, IOUT(S) ...................... 1.6 A Logic Supply Voltage VCC(D) ............... 6.0 V Operating Temperature Range, TA ..................................... 0C to +70C
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.
T C UY DL ON RO PE DC EN UE IN ER TF NE OR C IS OR DF --
SER DATA IN
SERIAL INTERFACE
SERVO CONTROL
ENERGY MANAGER
ADJUST
VOLTAGE REF.
V REF(X2)
V REF
Dwg. PP-048
Dwg. PP-048
The voice-coil function contains a 12-bit DAC, tunable low-pass and notch filters, and a full-bridge power driver. The MOS outputs provide increased available voltage and lower power dissipation over bipolar devices. Voice-coil current is sensed by internal circuitry that eliminates the need for an external current-sense resistor. Additional internal circuitry can be configured to provide an over-velocity fault limit by utilizing the internally monitored current of the voice-coil motor.
The spindle and voice-coil control functions are supplemented by an ENERGY MANAGERTM subsystem, which efficiently channels available power to protect the heads and the data disk during system failure or normal system shutdown. Synchronous rectification of spindle back-EMF voltage provides nearly lossless conversion of spindle rotational inertia into power to operate the voice coil motor for parking the heads. A dc-to-dc converter provides continuous operation at minimum supply voltages. In addition, the ENERGY MANAGER subsystem provides several sleep modes and latched fault states for undervoltage or thermal faults. The A8980CJT is supplied in a 64-lead thin quad flatpack for surface-mount applications.
FEATURES
Voice Coil Motor Driver: s Low rDS(on) MOS Outputs s Lossless Current Sensing s Zero Deadband s User-Adjustable Transconductance Gain s Retract Circuitry Functional to 0 V
8980 SUPERSERVOTM SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
FUNCTIONAL BLOCK DIAGRAM
ENERGY MANAGER
CONTROLLED RETRACT DC-DC CONVERSION SLEEP MODES UV FAULT THERMAL SHUTDOWN POWER-ON RESET (TO C) V REF 2V REF UV TRIP ADJUST
C SERIAL INTERFACE
OVER-VELOCITY FAULT
SERIAL DATA IN CLOCK DATA ENABLE
gm SERVO CONTROL
NOTCH FREQUENCY, DEPTH, & DAMPING TUNABLE LOW-PASS FILTER
12-BIT SERVODEMAND DAC
R
gm
2 MHz CLOCK
RETRACT
R gm
8-BIT SPIN-DEMAND DAC
IN / OUT MUX
CONFIGURATION CONTROL
ANALOG MUX 1 ANALOG MUX 2 DIGITAL MUX OUT
g
m
SLEW RATE CONTROL
BACK-EMF AND COMMUTATION LOGIC
EXTERNAL COMMUTATION TACH
Dwg. FP-028B
Spindle Motor Controller/Driver: s Low rDS(on) MOS Outputs s Back-EMF Circuitry Eliminates Hall-Effect Sensors s Programmable Slew Rate Eliminates Snubbers s Lossless Current Sensing s Improved Speed Disturbance Performance s Dynamic Braking with Delay s Active Braking Servo Compensator/Notch: s Over-Velocity Fault Circuitry s 12-Bit Servo-Demand DAC s Programmable Complex Pole Low-pass-Filter s Programmable Notch Frequency, Depth, and Damping
Energy Manager: s 3.0 V to 5.5 V Operation s Independent Power-Down (Sleep) Modes for all Functional Blocks s Efficient Synchronous Rectification Supplies Power During Blackout s Thermal Fault Shutdown Circuitry s Trimmed Bandgap Voltage Reference s Smart DAC Reference Generator s Programmable Voltage Reference for Relative Ground s Over-Velocity Fault Circuitry s Supply Under-Voltage Monitor with Adjustable Trip Point s System Diagnostics Data Out s Power-On Reset Generator
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright (c) 1992, 1994, Allegro MicroSystems, Inc.
8980 SUPERSERVOTM SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
FUNCTIONAL DESCRIPTION ACTUATOR
Servo-Demand DAC. A 12-bit DAC is provided to bridge the DSP "soft" domain to the analog hardware domain. The term "demand" refers to the distinction between the newly requested voice-coil current and the prior current being supplied. The DAC, operating in straight binary format, spans the full dynamic range between a large signal velocity and a precision position mode. The DAC output is updated synchronously with the notch functions to avoid the creation of aliasing products. Low-Pass Filter. This double, nonintrinsic complex-pole low-pass filter is provided to attenuate undesirable, out-ofband information. The input of this discrete time filter is sampled synchronously with the 12-bit DAC and notch function in order to avoid aliasing products. Notch Filter. This notch filter has a programmable center frequency and programmable notch depth to provide truly independent control of notch damping. Enough range and granularity are provided to allow versatile and accurate out-of-band attenuation of undesirable energy sources. Actuator Transconductance Amplifier. The final transconductance function of the voice-coil actuation signal path is achieved by monitoring the load current and generating an error voltage to drive a local gm amplifier control loop. The error voltage is scaled by an external precision resistor (Rgm(act)). This resistor does not carry load current and is intended only for accurate determination of the transconductance. The function is:
gm(act) = 5800 A/V Rgm(act) and I OUT = VSERVO * gm(ACT).
Actuator Power Outputs. The voice-coil output driver is a full-bridge power driver operating in a class-B mode. The power output devices are enhancement-mode MOS transistors. Special internal circuitry results in nearly zero cross-over distortion when switching from one source/sink pair to another.
VM L FLYBACK V DC+ V M V BOOST(H)
V BOOST(L) V CC(A) V BG TRIP ADJ VCC(D)
VCC(PWR)
V CC(A) UNDER-VOLTAGE FAULT
DC-TO-DC CONVERTER
POWER ON RESET
V BOOST(H) V BOOST(L) POR OUT
V BOOST(H) V BOOST(L) V DC
V BOOST(L)
ADJUST (FROM SERIAL INTERFACE) FILTERED V VEL V REF 2 V REF 2
V BG VCC(A)
RETRACT VOLTAGE REFERENCE
VOICE-COIL DRIVER V RETRACT SPINDLE MOTOR DRIVERS
V BOOST(L) BANDGAP VOLTAGE REFERENCE V BG
V BOOST(L)
V CC(A)
V REF + V REF -
OVER VELOCITY FAULT
RETRACT MODE
REFERENCE ADJUST
x2 VCC(A) /2
V REF(x2)
VCC(D) TJ V BG ADJUST (FROM SERIAL INTERFACE) THERMAL FAULT SHUTDOWN / SLEEP
V REF
8980 SUPERSERVOTM SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
SPINDLE
The spindle function is a three-phase back-EMF sensing motor controller and driver. During start-up, internal circuitry provides complete spindle control and drive. At speed however, an external microcontroller is used to provide speed (phase/frequency) detection as well as compensation. heads, actuator retract mode controlled by constant voltage, and several sleep modes. In addition, a power-on reset function and two programmable voltage references (VREF and V REF(x2)) are provided that are suitable for output to the user. An onboard dc-to-dc converter generates two regulated "high" (greater than the supply) voltages referred to as VBOOST(H) and VBOOST(L). These voltages supply critical functions with maximum immunity from supply variations.
ENERGY MANAGER
The management of available energy is provided by automatic operating modes envoked by the fault monitor or sleep-mode manager. The fault monitor consists of an over-velocity fault circuit, a VCC(A) undervoltage fault circuit, and a thermal fault circuit. The operating modes include VCC(PWR) isolation, active rectification of spindle back-EMF voltage to provide nearly lossless conversion of spindle rotational inertia into power to operate the voice-coil motor for parking the
SERIAL INTERFACE
The serial interface is used to alter the control state of the device from an external microcontroller or other digital CMOS source. In addition to the various operational and diagnostic control states (modes), all critical constants, variables, and parameters can be adjusted through this interface. The serial interface is a synchronous serial three-wire port with serial data input, clock, and load (active low) functions. When LOAD is high, the serial interface is disabled and the chip is not affected by changes in SER DATA IN or CLK SER. To write data to the serial interface, CLK SER should be low prior to LOAD going low. Once LOAD goes low, information at SER DATA IN is read into the shift register on the positive-going transitions of CLK SER.
TERMINAL FUNCTIONS
ANALOG SUPPLY DIGITAL SUPPLY LOAD SUPPLY
VCC(A) ; supplies all analog functions except for gate drive of power output transistors. For most applications, VCC(A) , VCC(D), and VCC(PWR) are connected together. VCC(D); supplies all digital functions. For most applications, V CC(A), VCC(D), and VCC(PWR) are connected together. VCC(PWR); supplies all voice-coil and spindle power output transistors. This terminal is internally connected to the source of the blocking FET used to isolate VM from V CC(PWR) on system failure or shutdown. For most applications, VCC(A), VCC(D), and VCC(PWR) are connected together. Substrate. This terminal must be connected to ground. Supplies power to the voice-coil and spindle power output transistors. Connect this terminal to the external flyback inductor for the dc-to-dc converter; internally connected to the drain of the blocking FET. External inductor for the dc-to-dc converter. Internally generated "high" voltage for driving the gates of all source-side power output transistors. This source is regulated and requires a compensation capacitor from this terminal to ground.
SUB VM
LFLYBCK VBOOST(H)
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8980 SUPERSERVOTM SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
VBOOST(L)
Internally generated intermediate voltage for driving the gates of all sink-side power output transistors, the bandgap reference, and fault monitors. This source is regulated and requires a compensation capacitor from this terminal to ground. Control voltage provided to drive the gate of an optional external enhancement-mode power FET, augmenting the internal blocking FET between VCC(PWR) and VM. Programmable reference voltage output. This reference tracks VREF(x2) and may be used as a relative signal ground. Programmable reference voltage output. Derived from a trimmed internal bandgap reference. May be used as the reference for system DAC and ADC. Power-on reset for the application system. Active low guaranteed by design to be active on power up. Also occurs as a result of VCC(A) degrading below the BLACKOUT under-voltage threshold. VUV (TRIP) ; trip threshold adjust input (an external resistor divider between VCC(A) and ground) for the under-voltage BLACKOUT fault monitor. A capacitor at this terminal can provide for time domain filtering. fCLK(2MHz); reference for all internal analog signal-processing functions. Affects frequency domain placement of all poles, zeros, and bandwidths. Non-inverting microcontroller serial-data input used for transferring data to all internal parameter and mode-control registers. fCLK(SER); reference for the serial data interface. Data is transferred on the positive-going edge of this clock. Active low. Begins and ends data transfer. Direct clock gating data from temporary internal latch to control register. This continuous time input is redundant to the XFR bit, which is embedded in the serial data format. It is internally synchronized to the fCLK(2MHz) positive-going edge. Analog input or output. Also used to drive internal nodes. Analog input or output. Also used to drive internal nodes for calibration and measurement on internal analog functions. Non-inverting digital multiplexer output. Used to probe internal nodes allowing precise timedomain measurements. Also used to extract internal status and diagnostic information. VOUT(P); voice-coil power output. Full-bridge differential complement to VOUT(N). VOUT(N) ; voice-coil power output. Full-bridge differential complement to VOUT(P). The voltage at this terminal is proportional to voice-coil actuator current.
VPF(GATE)
VREF
VREF(x2) POROUT
TRIP ADJ
CLK SER DATA IN CLK SER LOAD EXT XFR
AMUX1 AMUX2 DMUXOUT OUTP OUTN VSENS(act)
8980 SUPERSERVOTM SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
Rgm(act) RETRACT EXT ACT
A resistor between this terminal and VSENS(act) is used to adjust the forward transconductance gain of the voice-coil transconductance amplifier. Active high retract input from the system. Continuous-time direct input to cause immediate retract mode. VSERVO ; summing junction at the input of the voice-coil transconductance amplifier. This direct continuous-time input to the actuator gm amplifier provides diagnostic as well as feed-forward access. Operational amplifier inverting input. The non-inverting input is internally connected to VREF. Operational amplifier output. This undedicated operational amplifier functions in continuous time. Inverting input of operational amplifier portion of over-velocity fault circuit. Non-inverting input of operational amplifier portion of over-velocity fault circuit. VVEL; output of the over-velocity operational amplifier. Also internally connected to the inputs of two comparators that provide the positive and negative velocity fault thresholds. VOUT(A); spindle motor power output terminal. VOUT(B); spindle motor power output terminal. VOUT(C) ; spindle motor power output terminal. Connection to spindle motor center tap; provides the differential reference for detection of backEMF zero crossings. If this terminal is not connected, the device will internally simulate the centertap of the motor. The voltage at this terminal is proportional to the spindle motor current. A resistor connected from this terminal to VSENS(spin) provides for adjusting the forward transconductance gain of the spindle transconductance amplifier. A digital logic output that goes low to high on a back-EMF zero crossing; provides tach-like information to the spin controller. fsync; hard external commutation sequence start (positive-edge triggered). May be used to place spindle commutation edges in the inter-sector gap, or for phase-locking multiple spindle drivers. Vspin; direct continuous time input to the spindle transconductance amplifier/driver. Zero decurrent occurs at 2.00 V; full-scale positive demand current occurs at 4.00 V. Input for uncommitted analog switch. Output of uncommitted analog switch. Logic input for uncommitted analog switch; a high level connects SWIN to SWOUT.
OP1(IN) OP1(OUT) VELINN VELINP VEL OUTA OUTB OUTC C TAP
VSENS(spin) Rgm(spin) fcom EXT COM EXT SPIN
mand
SWIN SWOUT SWON
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8980 SUPERSERVOTM SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
ADDRESS MAP AND DATA BIT ASSIGNMENTS
Address Word 00H 01H Data Bit 0-3 4-7 0-5 6 7 0-3 4-7 0-7 8 04H 0-3 4-6 7 0-3 4-6 06H 0-3 4-7 07H 08H 09H 0AH 0-7 0 - 11 0-7 0-3 4 5 6-7 0BH 0-3 4-7 Function Blanking Time Commutation Delay Time Coast Time Commutation Multiplexer Not used at this time Startup Time Watchdog Time Spindle-Demand DAC Current Magnitude Reverse Commutation Mode Spindle Slew Rate Control Spindle Multiplexer Not used at this time Spindle Transconductance Amp. Bandwidth Spindle Transconductance Amp. Local Zero Internal 6.25 kHz Oscillator Frequency Trim Not used at this time Not used at this time Servo-Demand DAC Current Magnitude Not used at this time Low-Pass Filter Damping (Zeta) Control Not used at this time Low-Pass Filter Reset Control Not used at this time Notch Depth (3) Control Not used at this time 14H 13H 10H Address Word 0CH Data Bit 0-3 4 5-7 0-4 5-7 0EH 0-4 5-7 0FH 0-3 4-6 7 0-2 3-5 6-7 11H 12H 0-7 0-3 4-6 7 0-2 3-5 6-7 0-2 3 4 5-7 15H 0-2 Function Notch Width (Zeta DZ3) Control Notch Reset Control Not used at this time Low-Pass Filter Freq. Synth. (Dn2 ) Control Not used at this time Notch Center Frequency (Dn3 ) Control Not used at this time Actuator Bandwidth (BWACT) Control Actuator Zero (Damping) Control Not used at this time Retract Velocity Demand Voltage Actuator Analog Multiplexer Input Select Not used at this time Sleep Mode Manager Fault Control Monitor Programmable References Voltage Select Long Spindle Braking Delay Analog Multiplexer-2 Selection Digital Multiplexer Output Selection Not used at this time Analog Multiplexer-1 Selection Chopper Stabilization of LP & Notch Filters Disable actuator retract during fault Not used at this time Actuator Power Voltage Amplifier Deadband Trim
0DH
02H 03H
05H
8980 SUPERSERVOTM SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER
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. 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.
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

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