Data Sheet 26301.4 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING LOAD SUPPLY 1 C D2 2 C WD 3 CST 4 OUTA COMMUTATION DELAY 24 C D1 23 DATA IN 22 CLOCK 21 CHIP SELECT 5 20 RESET GROUND 6 19 GROUND GROUND 7 18 GROUND OUT B 8 MUX 17 DATA OUT OUT C 99 FLL 16 OSCILLATOR CENTERTAP 10 15 LOGIC SUPPLY BRAKE 11 14 SECTOR DATA C RES 12 13 FILTER SERIAL PORT V BB VDD BOOST CHARGE PUMP The A8906CLB is a bidirectional three-phase brushless dc motor controller/driver. The three half-bridge outputs are low on-resistance nchannel DMOS devices capable of driving up to 1 A. The A8906CLB provides complete, reliable, self-contained back-EMF sensing motor startup and running algorithms. A programmable digital frequencylocked loop speed control circuit together with the linear current control circuitry provides precise motor speed regulation. A serial port allows the user to program various features and modes of operation, such as the speed control parameters, rotational direction, startup current limit, sleep mode, diagnostic modes, and others. The A8906CLB is fabricated in Allegro’s BCD (Bipolar CMOS DMOS) process, an advanced mixed-signal technology that combines bipolar, analog and digital CMOS, and DMOS power devices. The A8906CLB is provided in a 24-lead wide-body SOIC batwing package. It provides for the smallest possible construction in surface-mount applications. PRELIMINARY INFORMATION Dwg. PP-040B ABSOLUTE MAXIMUM RATINGS at TA = +25°C Load Supply Voltage, VBB . . . . . . . . . . 14 V Output Current, IOUT . . . . . . . . . . . . ±1.25 A Logic Supply Voltage, VDD . . . . . . . . . 6.0 V Logic Input Voltage Range, VIN . . . . . . . . . . . -0.3 V to VDD + 0.3 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. FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ (Subject to change without notice) March 1, 1999 DMOS Outputs Low rDS(on) Startup Commutation Circuitry Back-EMF Commutation Circuitry Direction Control Serial Port Interface Frequency-Locked Loop Speed Control Sector Data Tachometer Signal Input Programmable Start-Up Current Diagnostics Mode Sleep Mode Linear Current Control Internal Current Sensing Dynamic Braking Through Serial Port Power-Down Dynamic Braking System Diagnostics Data Out Data Out Ported in Real Time Internal Thermal Shutdown Circuitry Always order by complete part number, e.g., A8906CLB . 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER FUNCTIONAL BLOCK DIAGRAM LOGIC SUPPLY C D1 C D2 C ST BRAKE 15 24 2 4 11 C RES 12 VDD BRAKE BOOST CHARGE PUMP 1 LOAD SUPPLY 5 OUT A 8 OUT B 9 OUTC VBB OUT B OUT C CENTERTAP 10 C WD 3 FCOM COMMUTATION DELAY SEQUENCE LOGIC COMMUTATION LOGIC OUT A START-UP OSC. BLANK WATCHDOG TIMER SECTOR 14 DATA 23 SERIAL PORT CLOCK CHIP SELECT ALLOWABLE PACKAGE POWER DISSIPATION in WATTS MUX 20 22 21 CURRENT CONTROL CHARGE PUMP 17 DATA OUT DATA IN FREQUENCYLOCKED LOOP RESET OSC 16 RS 1.5 R θJA = 55°C/W 0.5 0 75 100 TEMPERATURE in °C 125 GROUND Dwg. FP-034 RθJT = 6°C/W 50 18-19 FILTER 2.0 25 GROUND 13 2.5 1.0 6-7 TSD 150 Dwg. GP-019B 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1999 Allegro MicroSystems, Inc. 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER ELECTRICAL CHARACTERISTICS at TA = +25°C, VDD = 5.0 V Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units Logic Supply Voltage VDD Operating 4.5 5.0 5.5 V Logic Supply Current IDD Operating — 7.5 10 mA Sleep Mode — 250 500 µA Operating 4.0 — 14 V TJ — 165 — °C ∆TJ — 20 — °C VBB = 14 V, VOUT = 14 V — 1.0 300 µA VBB = 14 V, VOUT = 0 V — -1.0 -300 µA IOUT = 600 mA — 1.0 1.4 Ω VBB = 14 V, IOUT = IOUT(MAX), L = 3 mH 14 — — V IF = 1.0 A — 1.25 1.5 V Load Supply Voltage Thermal Shutdown Thermal Shutdown Hysteresis VBB Output Drivers Output Leakage Current Total Output ON Resistance (Source + Sink + RS) Output Sustaining Voltage Clamp Diode Forward Voltage IDSX rDS(on) VDS(sus) VF Control Logic Logic Input Voltage Logic Input Current DATA Output Voltage CST Current VIN(0) SECTOR DATA, RESET, CLK, -0.3 — 1.5 V VIN(1) CHIP SELECT, OSC 3.5 — 5.3 V IIN(0) VIN = 0 V — — -0.5 µA IIN(1) VIN = 5.0 V — — 1.0 µA VOUT(0) IOUT = 500 µA — — 1.5 V VOUT(1) IOUT = -500 µA 3.5 — — V Charging -9.0 -10 -11 µA — 500 — µA VCSTH 2.25 2.5 2.75 V VCSTL 0.85 1.0 1.15 V Charging -9.0 -10 -11 µA Discharging 9.0 10 11 µA Leakage, VFILTER = 2.5 V — — 5.0 nA 1.57 1.85 2.13 V Charging -18 -20 -22 µA Discharging 32 40 48 µA ICD(DISCHRG)/ICD(CHRG) 1.8 2.0 2.2 — 2.25 2.5 2.75 V ICST Discharging CST Threshold Filter Current Filter Threshold CD Current IFILTER VFILTERTH ICD (CD1 or CD2) CD Current Matching CD Threshold — VCDTH Continued next page … 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER ELECTRICAL CHARACTERISTICS continued Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units -9.0 -10 -11 µA CWD Current ICWD CWD Threshold Voltage VTL 0.22 0.25 0.28 V VTH 2.25 2.5 2.75 V VDD = 5.0 V, TA = 25°C 12 — — MHz D3 = 0, D4 = 0 1.0 1.2 1.4 A D3 = 0, D4 = 1 0.9 1.0 1.1 A D3 = 1, D4 = 0 0.5 0.6 0.7 A D3 = 1, D4 = 1 — 250 — mA 1.5 1.75 2.0 V — 20 — µA Max. FLL Oscillator Frequency IOUT(MAX) Charging fOSC — BRAKE Threshold VBRK BRAKE Hysteresis Current IBRKL VBRK = 750 mV Transconductance Gain gm 0.42 0.50 0.58 A/V Centertap Resistors RCT 5.0 10 13 kΩ VBEMF - VCTAP at 5.0 20 37 mV FCOM Transition -5.0 -20 -37 mV Back-EMF Hysteresis — SERIAL PORT TIMING CONDITIONS CHIP SELECT E A B CLOCK C D C D DATA Dwg. WP-019 A. Minimum CHIP SELECT setup time before CLOCK rising edge .......... 100 ns B. Minimum CHIP SELECT hold time after CLOCK rising edge ............... 150 ns C. Minimum DATA setup time before CLOCK rising edge ........................ 150 ns D. Minimum DATA hold time after CLOCK rising edge ............................. 150 ns E. Minimum CLOCK low time before CHIP SELECT .................................. 50 ns F. Maximum CLOCK frequency .............................................................. 3.3 MHz 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER TERMINAL FUNCTIONS Term. Terminal Name Function 1 LOAD SUPPLY VBB; the 5 V or 12 V motor supply. 2 CD2 One of two capacitors used to generate the ideal commutation points from the back-EMF zero crossing points. 3 CWD Timing capacitor used by the watchdog circuit to disable the back-EMF comparators during commutation transients, and to detect incorrect motor position. 4 CST Startup oscillator timing capacitor. 5 OUTA Power amplifier A output to motor. 6-7 GROUND 8 OUTB Power amplifier B output to motor. 9 OUTC Power amplifier C output to motor. 10 CENTERTAP 11 BRAKE 12 CRES External reservoir capacitor used to hold charge to drive the source drivers’ gates. Also provides power for brake circuit. 13 FILTER Analog voltage input to control motor current. Also, compensation node for internal speed control loop. 14 SECTOR DATA External tachometer input. Can use sector or index pulses from disk to provide precise motor speed feedback to internal frequency-locked loop. 15 LOGIC SUPPLY VDD; the 5 V logic supply. 16 OSCILLATOR 17 DATA OUT 18-19 GROUND 20 RESET 21 CHIP SELECT 22 CLOCK Clock input for serial port. 23 DATA IN Sequential data input for the serial port. 24 CD1 Power and logic ground and thermal heat sink. Motor centertap connection for back-EMF detection circuitry. Active low turns ON all three sink drivers shorting the motor windings to ground. External capacitor and resistor at BRAKE provide brake delay. Clock input for the speed reference counter. Typical max. frequency is 10 MHz. Thermal shutdown indicator, FCOM, TACH, or SYNC signals available in real time, controlled by 2-bit multiplexer in serial port. Power and logic ground and thermal heat sink. When pulled low forces the chip into sleep mode; clears all serial port bits. Strobe input (active low) for data word. One of two capacitors used to generate the ideal commutation points from the back-EMF zero crossing points. 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER FUNCTIONAL DESCRIPTION Power Outputs. The power outputs of the A8906CLB are n-channel DMOS transistors with a total source plus sink rDS(on) of typically 1 Ω. Internal charge pump boost circuitry provides voltage above supply for driving the high-side DMOS gates. Intrinsic ground clamp and flyback diodes provide protection when switching inductive loads and may be used to rectify motor back-EMF in power-down conditions. An external Schottky power diode or pass FET is required in series with the load supply to allow motor back-EMF rectification in power down conditions. Back-EMF Sensing Motor Startup and Running Algorithm. The A8906CLB provides a complete self-contained back-EMF sensing startup and running commutation scheme. The three half-bridge outputs are controlled by a state machine. There are six possible combinations. In each state, one output is high (sourcing current), one low (sinking current), and one is OFF (high impedance or ‘Z’). Motor back EMF is sensed at the OFF output. The truth table for the output drivers sequencing is: D2 Low D2 High Direction Control OUTA OUTB OUTC High Z Low Low Z High Low Low Z High High Z Z High High Z Low Low At startup, the outputs are enabled in one of the sequencer states shown. The back EMF is examined at the OFF output by comparing the output voltage to the motor centertap voltage at CENTERTAP. The motor will then either step forward, step backward, or remain stationary (if in a nulltorque position). If the motor moves, the back-EMF detection circuit waits for the correct polarity back-EMF zero crossing (output crossing through centertap). True back-EMF zero crossings are used by the adaptive commutation delay circuit to advance the state sequencer (commutate) at the proper time to synchronously run the motor. Back-EMF zero crossings are indicated by FCOM, an internal signal that toggles at every zero crossing. FCOM is available at the DATA OUT terminal via the programmable data out multiplexer. V OUTA V OUTB SOURCE ON V BACK-EMF VOLTAGE OUTC V SINK ON CTAP FCOM TOGGLES AT BACK-EMF ZERO CROSSING FCOM Dwg. WP-016-1 Direction Control. Serial port bit D2 controls the direction of rotation (see sequencer state table). The motor should be at a complete stop before beginning a startup sequence that reverses the direction of rotation. Startup Oscillator. If the motor does not move at the initial startup state, then it is in a null-torque position. In this case, the outputs are commutated automatically by the startup oscillator after a period set by the external capacitor at CST where tCST = 4(VCSTH - VCSTL) x CST IST(charge) + IST(discharge) In the next state, the motor will move, back EMF will be detected, and the motor will accelerate synchronously. Once normal synchronous back-EMF commutation occurs, the startup oscillator is defeated by pulses of pulldown current at CST at each commutation, which prevents CST from reaching its upper threshold and thus completing a cycle and commutating. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER Adaptive Commutation Delay. The adaptive commutation delay circuit uses the back-EMF zero-crossing indicator signal (FCOM) to determine an optimal commutation time for efficient synchronous operation. This circuit commutates the outputs, delayed from the last zero crossing, using two external timing capacitors, CD1 and CD2, Blanking and Watchdog Timing Functions. The blanking and watchdog timing functions are derived from one timing capacitor, CWD. VTL x CWD where tBLANK = ICWD and tWD = VTH x CWD ICWD The CWD capacitor begins charging at each commutation, initiating the BLANK signal. BLANK is an internal signal that inhibits the backEMF comparators during the commutation transients, preventing errors due to inductive recovery and voltage settling transients. t FCOM FCOM The watchdog timing function allows time to detect correct motor position by checking the back-EMF polarity after each commutation. If the correct polarity is not observed between tBLANK and tWD, then the watchdog timer commutates the outputs to the next state to synchronize the motor. This function is useful in preventing excessive reverse rotation, and helps in resynchronizing (or starting) with a moving spindle. VCWD tCD1 VCD1 t CD2 V TL V CWD VCD2 t BLANK BLANK Dwg. WP-016-2 Dwg. WP-022 to measure the time between crossings. ICD(charge) where tCD = tFCOM x ICD(discharge) CD1 charges up with a fixed current from its 2.5 V reference while FCOM is high. When FCOM goes low at the next zero crossing, CD1 is discharged at approximately twice the charging current. When CD1 reaches the CD threshold, a commutation occurs. CD2 operates similarly except on the opposite phase of FCOM . Thus the commutations occur approximately halfway between zero crossings. The actual delay is slightly less than halfway to compensate for electrical delays in the motor, which improves efficiency. NORMAL COMMUTATION VTH V TL V CWD t BLANK BLANK t WD Dwg. WP-021 WATCHDOG-TRIGGERED COMMUTATION 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER Current Control. The A8906CLB provides linear current control via the FILTER terminal, an analog voltage input. Maximum current limit is also provided, and is controlled in four steps via the serial port. Output current is sensed via an internal sense resistor (RS). The voltage across the sense resistor is compared to one-tenth the voltage at the FILTER terminal less the filter threshold voltage, or to the maximum current limit reference, whichever is lower. This transconductance function is IOUT = (VFILTER -VFILTERTH) / 10RS, where RS is nominally 0.2 Ω and VFILTERTH is approximately 1.85 V. YANK POWER UP S ERROR FAST FROM FLL R SEQUENTIAL LOGIC Q C RES SPEED-CONTROL INITIALIZATION V DD V DD Ic – FILTER + – x1 Id VI max – C ÷10 MUX C F1 1.85 V F2 LINEAR CURRENT CONTROL + RS FROM SERIAL PORT REGISTER D3 AND D4 CHARGE PUMP ERROR FAST FROM FLL MAX CURRENT LIMIT Dwg. EP-046 Speed Control. The A8906CLB includes a frequency-locked loop speed control system. This system monitors motor speed via internal or external digital tachometer signals, generates a precision speed reference, determines the digital speed error, and corrects the motor current via an internal charge pump and external filtering components on the FILTER terminal. A once per revolution TACH signal can be generated by counting cycles of FCOM (the number of motor poles must be selected via the serial port). TACH is then a jitter-free signal that toggles once per motor revolution. The rising edge of TACH triggers REF, a precision speed reference derived by a programmable counter. The duration of REF is set by programming the counter to count the desired number of OSC cycles SECTOR FCOM COUNT (3 x MOTOR POLES) D20 & D21 MUX ÷2 TACH ONCE-AROUND PULSE D19 REF TACH SERIAL PORT REGISTER ERROR SLOW D5–D18 REF OSC 4-BIT FIXED COUNTER 14-BIT PROGRAMMABLE COUNTER The speed error is detected as the difference in falling edges of TACH and REF. The speed error signals control the error-correcting charge pump on the FILTER terminal, which drive the external loop compensation components to correct the motor current. OUT + ERROR SLOW FROM FLL RF1 VBB BOOST CHARGE PUMP 60 x fOSC desired = total count desired motor speed (rpm) where the total count (number of oscillator cycles) is equal to the sum of the selected (programmed low) count numbers corresponding to bits D5 through D18. TACH REF Sector Mode. An external tachometer signal, such as sector or index pulses, may be used to create the TACH signal, rather than the internally derived once around. To use this mode, the signal is input to the SECTOR terminal, and the sector mode must be enabled via the serial port. When Switching from the once-around mode to sector mode, it is important to monitor the SYNC signal on DATA OUT, and switch modes only when SYNC is low. This ensures making the transition without disturbing the speed control loop. The speed reference counter should be reprogrammed at the same time. Speed Loop Initialization (YANK). To improve the acquire time of the speed control loop, there is an automatic feature controlled by an internal YANK signal. The motor is started at the maximized programmed current by bypassing the FILTER terminal. The FILTER terminal is clamped to an internal reference (the filter threshold voltage), initializing it near the closed loop operating point. YANK is enabled at startup and stays high until the desired speed is reached. Once the first error-fast occurs, indicating the motor crossed through the desired speed, YANK goes low. This releases the clamp on the FILTER terminal and current control is returned to FILTER. This feature optimizes speed acquire and minimizes settling. The Current Control Block Diagram illustrates the YANK signal and its effects. ERROR FAST Dwg. EP-045 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER Serial Port. The serial port functions to write various operational and diagnostic modes to the A8906CLB. The serial port DATA IN is enabled/disabled by the CHIP SELECT terminal. When CHIP SELECT is high the serial port is disabled and the chip is not affected by changes in data at the DATA IN or CLOCK terminals. Bit Number D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15 D16 D17 D18 To write data to the serial port, the CLOCK terminal should be low prior to the CHIP SELECT terminal going low. Once CHIP SELECT goes low, information on the DATA IN terminal is read into the shift register on the positive-going transition of the CLOCK. There are 24 bits in the serial input port. Data written into the serial port is latched and becomes active upon the low-to-high transition of the CHIP SELECT terminal at the end of the write cycle. D0 will be the last bit written to the serial port. SERIAL PORT BIT DEFINITIONS D0- Sleep/Run Mode; LOW = Sleep, HIGH = Run This bit allows the device to be powered down when not in use. D1- Step Mode; LOW = Normal Operation, HIGH = Step Only When in the step-only mode the back-EMF commutation circuitry is disabled and the power outputs are commutated by the startup oscillator. This mode is intended for device and system testing. D20 and D21-These bits program the number of motor poles for the once-around FCOM counter: D3 and D4 - These two bits set the output current limit: D4 Current Limit 0 0 1 1 0 1 0 1 1.2 A 1A 600 mA 250 mA D5 thru D18-This 14-bit word (active low) programs the desired motor speed. 16 32 64 128 256 512 1 024 2 048 4 096 8 192 16 384 32 768 65 536 131 072 D19-Speed-control mode switch; LOW = internal once-around speed signal, HIGH = external sector data. D2- Direction; LOW = Forward, HIGH = Reverse. D3 Count Number D20 D21 Motor Poles 0 0 1 1 0 1 0 1 8 4 16 12 D22 and D23-Controls the multiplexer for DATA OUT: REF time to set D22 D23 DATA OUT 0 0 1 1 0 1 0 1 TACH (once around or sector) Thermal Shutdown SYNC FCOM Reset. The RESET terminal when pulled low clears all serial port bits, including the D0 latch, which puts the A8906CLB in the sleep mode. 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER BRAKE FAULT V FAULT inherent capacitive input, the three sink drivers will remain active until the device is reset. BRAKE ACTIVATED – VD CB R VBRK B t BRK tBRK = RBCB VBRK 1 – ln V FAULT - VD Dwg. OP-004 Centertap. The A8906CLB internally simulates the centertap voltage of the motor. To obtain reliable start-up performance from motor to motor, the motor centertap should be connected to this terminal. Braking. A dynamic braking feature of the A8906CLB shorts the three motor windings to ground. This is accomplished by turning the three source drivers OFF and the three sink drivers ON. Activation of the brake can be implemented through the BRAKE input. The supply voltage for the brake circuitry is the CRES voltage, allowing the brake function to remain active after power failure. Power-down braking with delay can be implemented by using an external RC and other components to control the brake terminal, as shown. Brake delay can be set using the equation below. Once the brake is activated, due to the External Component Selection. Applications information regarding the selection of external component values is available from the factory for external component selection, frequency-locked loop speed control, and commutation delay capacitor selection. TYPICAL APPLICATION V BB BYPASS 1 C D2 CWD C ST VBB COMMUTATION DELAY CB RB 22 CLOCK 21 CHIP SELECT 5 20 RESET 6 19 7 18 3 4 BYPASS 8 MUX 17 DATA OUT 99 FLL 16 OSC (REF) 11 12 CRES 0.22 µF CD1 DATA IN VDD 10 FAULT 24 23 2 SERIAL PORT VRET BOOST CHARGE PUMP 15 +5 V R F1 14 CF1 SECTOR DATA 13 CF2 Dwg. EP-036C 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER Dimensions in Inches (for reference only) 24 13 0.0125 0.0091 0.491 0.394 0.2992 0.2914 0.050 0.016 0.020 0.013 1 2 3 0.050 0.6141 0.5985 0° TO 8° BSC NOTE 1 NOTE 3 0.0926 0.1043 0.0040 MIN. Dwg. MA-008-25 in Dimensions in Millimeters (controlling dimensions) 24 13 0.32 0.23 10.65 10.00 7.60 7.40 1.27 0.40 0.51 0.33 1 2 3 15.60 15.20 1.27 BSC 0° TO 8° NOTE 1 NOTE 3 2.65 2.35 0.10 MIN. Dwg. MA-008-25A mm NOTES: 1. Webbed lead frame. Leads 6, 7, 18, and 19 are internally one piece. 2. Lead spacing tolerance is non-cumulative. 3. Exact body and lead configuration at vendor’s option within limits shown. 8906 BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/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