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8281 AND 8282
A8282SLB
NC OLF VBULK NC NC GND GND SENSE LNB LX VIN TCAP 1 2 3 24 23 22 EXTM VINT PUMPX VPUMP CPUMP GND GND ENT EN VSEL0 VSEL1 LLC
LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
Intended for analog and digital satellite receivers, these low-noise block converter regulators (LNBRs) are monolithic linear and switching voltage regulators specifically designed to provide the power and interface signals to the LNB down converter via the coaxial cable. If the device is in standby mode (EN terminal low), the regulator output is disabled, allowing the antenna down converters to be supplied or controlled by other satellite receivers sharing the same coaxial cable. In this mode, the device will limit the output reverse current. The A8281SLB output is set to 13 or 18-V by the VSEL terminal. It is supplied in a 16-lead SOIC power-tab package. The power tabs are at ground potential and need no electrical isolation. The A8282SLB output is set to 12, 13, 18, or 20-V by the VSEL terminals. Additionally, it is possible to increase the selected voltage by 1-V to compensate for the voltage drop in the coaxial cable (LLC terminal high). It is supplied in a 24-lead SOIC power-tab package. The power tabs are at ground potential and need no electrical isolation. The A8282SLB is an improved version of the A8283SLB, without a bypass switch.
Data Sheet 27448.2c
CHARGE PUMP
BUCK REG.
4 5 6 7 8 9 9 10 11 12
21 20 19 18 17 16 15 14 13
VOLTAGE CONTROL
Dwg. PP-072-2
FEATURES s LNB selection and standby function s Built-in tone oscillator factory trimmed to 22-kHz, facilitates DiSEqCTM (a trademark of EUTELSAT) encoding s Tracking switch-mode power converter for lowest dissipation s Externally adjustable short-circuit protection s LNB short-circuit protection and diagnostics s Auxiliary modulation input s Internal over-temperature protection s Reverse-current protection s Cable length compensation (A8282SLB only)
ABSOLUTE MAXIMUM RATINGS at TA = +25C
Supply Voltage, VIN ........................... 47-V Output Current, ILNB .... Internally Limited Output Voltage Range, VLNB .. -1-V to +22-V Logic Input Voltage Range, VI ................................... -0.3-V to +7-V Flag Output Voltage, VOLF ................... 7-V Operating Temperature Range, TA ................................. -20C to +85C Junction Temperature, TJ ................ +150C Storage Temperature Range, TS .............................. -55C to +150C
These devices incorporate features that have patents pending.
Always order by complete part number, e.g., A8282SLB .
8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
FUNCTIONAL BLOCK DIAGRAM and typical application
100 H 0.1 F
CPUMP PUMPX
0.1 F
VPUMP
VIN
100 F
LX
100 F
VINT (A8282 ONLY)
4.7 F
VOLTAGE REG.
CHARGE PUMP -
BOOST VOLTAGE
BUCK CONV.
- + OVERCURRENT
EN
5V 176 kHz
7V VREF
- +
135 mV
+ 352 kHz
VBULK
SENSE
+
VIN 47 V MAX
RS 200 m +
DiSEqC TERMINATION + + - LNB 5 k
100 nF
/2 ENT
25 k
-
900 mV
15 180 H
0.22 F
/8 & WAVESHAPING
22 kHz TONE
EXTM TSD OLF OVERCURRENT 5 k 1 k 0.1 F
LLC (A8282 ONLY)
VSEL0 (A8282 ONLY)
VSEL1
TCAP 10 nF
Dwg. FP-051-2
A8281SLB
A8281SLB Output Voltage Select Table
VSEL1 L H VLNB 13 V 18 V
EXTM OLF VBULK GND SENSE LNB LX VIN
1
CHARGE PUMP
16 15 14 13 12 11 10 9
PUMPX VPUMP CPUMP GND ENT EN VSEL1 TCAP
2 3 4 5 6 7 8 BUCK REG.
A8282SLB Output Voltage Select Table
VSEL0 L L L L H H H H VSEL1 L L H H L L H H LLC L H L H L H L H VLNB 13 V 14 V 18 V 19 V 12 V 13 V 20 V 21 V
VOLTAGE CONTROL
Dwg. PP-072-3
2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright (c) 2003 Allegro MicroSystems, Inc.
8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
ELECTRICAL CHARACTERISTICS: unless otherwise noted at TJ < 125C, CLNB = 0.1 F, 4.5-V + VLNB < VIN < 47-V
Limits Characteristic Supply Voltage Range Output Voltage Error (reference Output Voltage Select table) Output Reverse Current Buck Switch On Resist. Buck Switch Current Limit Switching Frequency Linear Reg. Volt. Drop Logic Input Voltage Logic Input Current Supply Current Tone Characteristics Tone Frequency Tone Amplitude Tone Duty Cycle Tone Rise or Fall Time External Modulation Tone Amplitude External Modulation Input Voltage Range External Modulation Input Impedance ftone Vtone(PP)(ENT) dctone tr, tf ENT = H ENT = H, 12 mA ILNB 750 mA ENT = H, 12 mA ILNB 750 mA ENT = H, 12 mA ILNB 750mA 20 400 40 5 400 22 650 -- 10 550 24 900 60 15 800 kHz mV % s mV Symbol VIN EVLNB Operating 6 mA ILNB 750 mA, ENT = L 12 mA ILNB 750 mA, ENT = H, average VLNB IRLNB rDS(on) IBSM fO VBUCK VIL VIH IIH IIN VIH = 5 V Outputs disabled (EN = L) EN = H, ILNB = 0 16 x ftone VSENSE - VLNB, ENT = L, ILNB = 750 mA EN = L, VLNB = 22 V, VIN = 22 V or floating TJ = 25C, ILNB = 750 mA TJ = 125C, ILNB = 750 mA Test Conditions Min. 4.5 +VLNB -- -- -- -- -- 1 320 700 -- 2 -- -- -- Typ. -- 0 0 1 0.57 0.84 -- 352 900 -- -- <1.0 0.25 6 Max. 47 4.5 4.5 5 0.67 0.94 2.5 384 1100 0.8 -- 10 1 10 Units V % % mA A kHz mV V V A mA mA
Vtone(PP)(EXTM) f = 22 kHz square wave, ILOAD = 12 mA to 450 mA, VIN = 100mV to 125 mV; VPP ac coupled VEXTM(PP) ZEXTM AC coupled f = 22 kHz
100 4
-- --
125 10
mV k
continued next page
NOTES: 1. Typical data is for design information only. 2. Negative current is defined as coming out of (sourcing) the specified device terminal.
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8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
ELECTRICAL CHARACTERISTICS: unless otherwise noted at TJ 125C, CLNB = 0.1-F, 4.5-V + VLNB VIN 47-V.
Limits Characteristic Protection Circuitry Current-Limiting Threshold Overload Flag Output Low Overload Flag Leakage Current Thermal Shutdown Temp. Thermal Shutdown Hysteresis VILNB(th) VOLF IOLF TJ TJ VBULK - VSENSE IOLF = 8-mA VOLF = 5.5-V 115 -- -- -- -- 135 0.28 <1.0 165 20 155 0.5 10 -- -- mV V A C C Symbol Test Conditions Min. Typ. Max. Units
NOTES: 1. Typical data is for design information only. 2. Negative current is defined as coming out of (sourcing) the specified device terminal.
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115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
FUNCTIONAL DESCRIPTION Buck regulator. A current-mode buck converter provides the linear regulator a supply voltage that tracks the selected LNB output voltage. The buck converter operates at 16 times the internal tone frequency, nominally 352-kHz. The tracking regulator provides minimum power dissipation across the range of output voltages by adjusting the SENSE terminal voltage, nominally 900-mV above the LNB output voltage. The tracking regulator also provides adequate headroom for tone injection. Linear regulator. The output linear regulator will sink or source current. This allows tone modulation into a capacitive load of 0.1-F over the output current range of 12-mA to 750-mA. Slew rate control. The programmed output voltage rise and fall times can be set by an external capacitor (with an internal 25-k resistor) located on the TCAP terminal. The range of acceptable capacitor values is 4.7-nF to 47-nF. This feature only affects the turn-on and programmed voltage rise and fall times. Modulation is unaffected by the capacitor. If LNB output voltage rise and fall time limiting is not required, the TCAP terminal should use a 100-nF ceramic as a default value to minimize output noise. If a small value capacitor is used, the rise time will be limited by the time required to charge the VBULK capacitor. Short-circuit limit regulator. The LNB output is current limited. The short-circuit protection threshold is set by the value of an external resistor, RS, in conjunction with an internal 135-mV reference voltage (VILNB(th)). RS = 0.135/ILNBM where ILNBM is the desired current-limit value. The sense resistor should be chosen based on the maximum dc plus ac (tone) load current required, internal VILNB(th) tolerance, and sense resistor accuracy. For 750-mA applications, a precision 140-m resistor is recommended. For 500-mA applications, the resistor value can be raised to 200-m. In operation, the short-circuit protection produces current limiting at the input due to the tracking converter. If the output is shorted, the linear regulator will limit the output current to ILNBM. Fault output. Short-circuit or thermal shutdown will cause the OLF terminal, an open-drain diagnostic output flag, to go LOW. Internal tone modulation. The ENT (tone enable) terminal activates the internal tone signal, modulating the dc output with a 650-mV peak-to-peak trapezoidal waveform. The internal oscillator is factory trimmed to provide a tone of 22-kHz. No further adjustment is required. Burst coding of the tone can be accomplished, due to the fast response of the ENT input and rapid tone response. This allows implementation of the DiSEqCTM protocols. External tone modulation. To improve design flexibility and to allow implementation of proposed LNB remote control standards, an analog modulation input terminal is available (EXTM). An appropriate dc-blocking capacitor must be used to couple the modulating signal source to the EXTM terminal. The peak-to-peak input amplitude should stay within 100-mV to 125-mV to ensure the DiSEqC amplitude specification over the output current range. If external modulation is not used, the EXTM terminal should be decoupled to ground with a 0.1-F ceramic capacitor.
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8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
APPLICATIONS INFORMATION
Component selection: Input capacitor, CIN. An electrolytic capacitor should be located as close to the device VIN terminal as possible. The input current is a square wave with fast rise and fall times so the capacitor must be able to handle the rms current without excessive temperature rise. The value of this capacitor is not as important as the ESR. The worst-case current is with maximum load current, minimum VIN, and maximum VLNB (highest switch duty cycle). Choose a capacitor with a ripple current rating greater than Icin = ILNB x 1.2 x VLNB(max)/VIN(min) Buck inductor, L1. A 100-H power inductor is appropriate for all operating conditions. The rated saturation current of the inductor must be greater than 1.3-A. To maximize efficiency, the dc resistance should be less than 350-m. Clamp diode, D1. A Schottky diode is required at the switching node LX. This diode should be rated at 1.5 times the maximum load current. Output capacitor, CBULK. A low-ESR (<200-m) electrolytic capacitor is recommended to minimize the ripple voltage. Less than 50-mV peak-to-peak is a reasonable goal. Vripple(PP) = ESR x Iripple(max) where Iripple(max) = VBULK(min) x (1 - [VBULK(min)/VIN(max)]) / (L1 x 352-kHz). Output capacitor, CLNB. Increasing the output capacitance, CLNB, will attenuate noise. However, this is limited by the requirement for low cable capacitance for 22-kHz tone transmission. Also, because the linear regulator sink current is limited, high values of output capacitance combined with low levels of output current can cause overshoot
of the 22-kHz tone. Operating points above the line in the following graph will not have excessive overshoot.
125
100
OUTPUT CURRENT IN mA
75 MINIMAL OVERSHOOT 50 EXCESSIVE OVERSHOOT 25
0 0 0.5 1.0 1.5
Dwg. GP-074
OUTPUT CAPACITANCE IN F
Layout notes:
1. The printed wiring board should use a heavy ground plane. A two-sided board with ground planes on both sides of the board is most desirable. Several copper vias under the device can be used to connect the ground planes and enhance thermal performance. 2. For optimum electrical and thermal performance, the device should be soldered directly onto the board. 3. Keep the sense resistor traces as short and as wide as possible to lower trace resistance. 4. Connect the bypass capacitors as close to the device as possible. The lower value ceramic capacitors should be closer to the device than the electrolytics. The supply voltage, VIN, should be decoupled with an electrolytic capacitor placed as close to the device as possible. 5. Place the TCAP capacitor as close to the device as possible.
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115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
APPLICATIONS INFORMATION (cont'd)
Grounding. Use a star ground approach at the device ground terminals. This allows the analog and power grounds to be kept separate on the PWB up to the device. Noise immunity. LNB systems can have a 50-mV peak specification for noise on the coaxial cable. This is easily achievable with proper layout and following a few guidelines: 1. Use a low-ESR capacitor for VBULK. A maximum of 200-m is recommended. 2. The LNB output is sensitive to the TCAP reference terminal. Keep the PWB traces short and location of CTCAP close to the device. This terminal is a high-impedance node and noise can be induced from proximity to an unshielded inductor. If the inductor can not be placed far enough away to avoid noise pickup, it is important to ensure that the induced voltage is out of phase with the switching node LX. Rotating the inductor can change the phase of the induced voltage. 3. Be sure to place a 1-F to 10-F capacitor on internal reference VINT (A8282 only). 4. Bypass EXTM with a 0.1-F ceramic capacitor to ground. 5. Increasing the output capacitance will attenuate noise. However, this must be traded off with the requiremnent for low cable capacitance for 22-kHztone transmission.
DirecTV(R). With the A8282, it is possible to raise the LNB output voltage 440-mV from the nominal 13-V setting to comply with DirecTV requirements. This is accomplished by connecting a 1-M resistor between the VINT and TCAP terminals, sourcing approximately 2.76-A into the TCAP node. The LNB output voltage is approximately six times the setting of the voltage-select DAC as shown in the figure.
VINT
1 M
VOLTAGE REG.
TCAP 25 k VOLTAGE SELECT - X6 + LNB
Dwg. EP-074
DiSEqCTM. The 22-kHz tone is specified to be compatible with EUTELSAT coaxial cable bus standards. The LNB output will be able to drive the DiSEqC termination network. The inductor must pass the dc current with minimal loss while the parallel resistor provides the recommended source impedance at 22-kHz. Unidirectional communication systems such as DiSEqC 1.0 do not need this termination and the LNB can be directly connected to the coaxial cable. 13-V to 18-V transition. The LNB output can be rapidly switched between a high and a low setting as a method of receiver-to-LNB communication. The TCAP capacitor will control the slew rate based on the RC charging. tr or tf = 25 x 103 x CTCAP ln(VLNB(H)/VLNB(L))
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8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
APPLICATIONS INFORMATION (cont'd)
Small values of TCAP are used when the desired transition time is less than a millisecond. In this case, the minimum rise time is limited by the charge time of the switching regulator output capacitor. This is dependent on the LNB load current, peak current limit in the buck switch, and the output amplitude change. tr = CBULK (VLNB(H) - VLNB(L))/I(AV) where I(AV) is the average current available to charge the output capacitor and can be estimated by I(AV) = 1.4 - ILNB. Note that this is only a limitation due to the ability to charge the output capacitor on a low-tohigh change of the LNB voltage. For high-to-low transitions, the output voltage will be slew limited by TCAP. The minimum value for CTCAP is 4.7-nF. Power dissipation. The power dissipated, and operating junction temperature of the device, can be estimated to ensure that the device is operating within the desired thermal budget. The total device power dissipation (PD) is comprised of three components: PD = PD(bias) + PD(lin) + PD(buck) where PD(bias) = VIN (IIN - 0.004), PD(lin) = VBUCK x ILNB, PD(buck) = ILNB2 x rDS(on) x VBULK/VIN where VBULK = VBUCK + (ILNB x RS) + VLNB. The device junction temperature can then be estimated as TJ = (PD x RJA) + TA or TJ = (PD x RJT) + TT
where TT is the power tab temperature (leads 4 or 13 for the A8281SLB or leads 6, 7, 18, or 19 for the A8282SLB) and RJT is 6C/W. Package thermal resistances, RJA, measured on JEDEC standard "high-K" four layer board: A8281SLB ..................................... 38C/W A8282SLB ..................................... 35C/W measured on two-sided PWB with 3 square inches (1935 mm2) copper ground area on each side: A8281SLB ..................................... 48C/W A8282SLB ..................................... 45C/W
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115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
APPLICATIONS INFORMATION (cont'd)
+5 V 5 k OLF C1 1 24 CINT R1 23 22
CHARGE PUMP
A8282SLB
2 3 4 5
RS
TCAP C2 C3
CBULK
+
21 20 19 18 17 16 ENT ENB VSEL0 VSEL1 LLC 0.22 F
VIN
6
L1
7 8
CBYP
ANALOG GROUND
9 9 10 11 BUCK REG.
VOLTAGE CONTROL
D1 +
15 14 13
CIN
12 CTCAP
POWER GROUND
Dwg. EP-072
VIN +30 V
CLNB
15
D2
180 H
L2
DiSEqC TERMINATION
Typical application
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8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
APPLICATIONS INFORMATION (cont'd)
Parts list for typical application
Description C1, C2, C3, CBYP, CLNB CIN CBULK CINT D1 D2 L1 100-F/50-V low-ESR electrolytic 100-F/35-V low-ESR electrolytic 4.7-F/16-V tantalum electrolytic 1-A/40-V Schottky diode 1.2-A/100-V fast-recovery diode 100-H (750-mA max. load) Sanken EK04 Sanken EU 2YX TDK TSL1112-101K1R4, or Coilcraft D03316P-104LW 100-H (500-mA max. load) L2 RS CTCAP R1 180-H (750-mA max. load) 140-m to 200-m/0.25-W 10-nF ceramic X7R/X5R 1-M, 5% (optional, see page 7) TDK TSL0808-101KR80 TDK TSL1112S-181K1R0-PF Meritek CR04RxxxF Nichicon UHD1H101MPT Nichicon UHC1V101 0.1-F/50-V ceramic X7R/X5R Representative Component
DiSEqC (Digital Satelite Equipment Control) is a trademark of EUTELSAT (European Telecommunications Satellite Corporation), Paris, France. DirecTV is a trademark of DirecTV, Inc., a unit of Hughes Electronics Corp., El Segundo, CA
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115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
Terminal List A8281SLB Terminal Terminal Name Number
NC OLF VBULK NC GND SENSE LNB LX VIN TCAP LLC VSEL1 VSEL0 EN ENT GND CPUMP VPUMP PUMPX VINT EXTM - 2 3 - 4 5 6 7 8 9 - 10 - 11 12 13 14 15 16 - 1
A8282SLB Terminal Number
1 2 3 4, 5 6, 7 8 9 10 11 12 13 14 15 16 17 18, 19 20 21 22 23 24
Terminal Description
No (internal) connection Overload flag output: low (fault) when ILNB > ILNBM or TJ > 165C, high when ILNB < ILNBM and TJ < 130C Tracking supply voltage to linear regulator No (internal) connection Ground and substrate Current limit setup resistor Output voltage to LNB Inductor drive point Supply input voltage (minimum, VLNB + 2.5-V) Capacitor for setting the rise and fall time of the outputs for line-length compensation Logic input: output voltage select Logic input: output voltage select Logic input: output voltage select Logic input: when high, enables device Logic input: when high, enables internal 22-kHz modulation Ground and substrate High side of charge-pump capacitor Gate-supply voltage for high-side drivers Charge-pump drive Bypass capacitor for internal voltage reference External modulation input
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8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
A8281SLB
Dimensions in Inches (for reference only)
16 9 0.0125 0.0091
0.2992 0.2914
0.419 0.394
0.050 0.016 0.020 0.013 1 2 3 0.4133 0.3977 0.050
BSC
0 TO 8
0.0926 0.1043 0.0040 MIN.
Dwg. MA-008-16A in
Dimensions in Millimeters (controlling dimensions)
16 9 0.32 0.23
7.60 7.40
10.65 10.00
1.27 0.40 0.51 0.33 1 2 3 10.50 10.10 1.27
BSC
0 TO 8
2.65 2.35 0.10 MIN.
Dwg. MA-008-16A mm
NOTES: 1. 2. 3. 4.
Exact body and lead configuration at vendor's option within limits shown. Lead spacing tolerance is non-cumulative. Leads 4 and 13 are internally one piece. Supplied in standard sticks/tubes of 47 devices or add "TR" to part number for tape and reel.
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115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
A8282SLB
Dimensions in Inches (for reference only)
24 13 0.0125 0.0091
0.2992 0.2914
0.419 0.394 0.050 0.016
0.020 0.013
1
2
3
0.6141 0.5985
0.050
BSC NOTE 1 NOTE 3
0 TO 8
0.0926 0.1043 0.0040 MIN.
Dwg. MA-008-25A in
Dimensions in Millimeters (controlling dimensions)
24 0.32 0.23
7.60 7.40
10.65 10.00 1.27 0.40
0.51 0.33
1
2
3
15.60 15.20
1.27
BSC NOTE 1 NOTE 3
0 TO 8
2.65 2.35 0.10 MIN.
Dwg. MA-008-25A mm
NOTES: 1. 2. 3. 4.
Exact body and lead configuration at vendor's option within limits shown. Lead spacing tolerance is non-cumulative. Webbed lead frame. Leads 6, 7, 18, and 19 are internally one piece. Supplied in standard sticks/tubes of 31 devices or add "TR" to part number for tape and reel.
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8281 AND 8282 LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS
The products described here are manufactured under one or more U.S. patents or U.S. patents pending. 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 performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use.
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115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

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