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Part: A8282SLBTR
Category:
Description: LNB Supply And Control-voltage Regulator
Company: Allegro Micro Systems, Inc.
Datasheet: Download A8282SLBTR datasheet File size : 227 kB
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LNB SUPPLY AND CONTROL VOLTAGE REGULATOR
11/18/2002 Intended for analog and digital satellite receivers, the low noise block converter regulator (LNBR) is a monolithic linear and switching voltage regulator, specifically designed to provide the power and the interface signals to the LNB downconverter via the coaxial cable. If the device is in stand-by mode (EN terminal LOW), the regulator output is disabled. This is to allow the antenna downconverters to be supplied/controlled by other satellite receivers sharing the same coaxial cable. In this mode the device will limit reverse current. The A8281 is supplied in a 16-lead plastic SOIC with copper batwing tab (suffix "LB"). The A8282 is supplied is a 24-lead plastic SOIC with copper batwing tab (suffix "LB"). Operating temperature range is standard classification (suffix "S"). The A8282 is available for improved power dissipation as well as allowing direct replacement of Allegro's first generation LNBR device, the A8283SLB, with the exception of the bypass switch.
ABSOLUTE MAXIMUM RATINGS at TA = +25°C
Load Supply Voltage, VIN ... 47 V Output Current, IOUT... Internally Limited* Output Voltage, VOUT...... -1V to 22 V Switching Node, LX ......-1V Logic Input .... -0.3 V to 7 V Package Power Dissipation (TA = +25°C), PD A8281SLB.. 56 °C/W** A8282SLB.. 50 °C/W** Operating Temperature Range, TA ........ -20°C to +85°C Junction Temperature, TJ ....... +150°C Storage Temperature Range, TS....... -55°C to +150°C
* Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the specified current rating or a junction temperature of 150°C. ** Measured on a PCB with 2 oz copper with ground area of 1 square inch.
FEATURES
LNB selection and stand-by function Built-in tone oscillator factory trimmed to 22 kHz facilitates DiSEqCTM encoding Tracking switch-mode power converter for lowest dissipation Externally adjustable short-circuit protection LNB short-circuit protection and diagnostics Auxiliary modulation input Internal over temperature protection Reverse current protection Cable Length Compensation (A8282 only)
This device incorporates features that have patents pending.
Always order by complete part number: Part Number A8282SLBTR A8282SLB A8281SLB Package 24 Lead SOIC Tape/Reel 24 Lead SOIC 16 Lead SOIC
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100uH .1uF CPUMP PUMPX .1uF VPUMP VIN +VIN 100uF 100uF 200 mohm LX VBULK SENSE EN (8282 Only) VINT 5V Regulator Charge Pump 4.7uF 352Khz Divide by 2 Buck Converter + 900mV 15 180uH Over Current + 135mV
ENT
OLF TSD OverCurrent Output Voltage Select EXTM .1uF
Fault
(8282 only) VSEL0
(8282 only) LLC
VSEL1
GND
TCAP 10nF
Output Voltage Select Table A8282SLB
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 14 18 19 12 13 20 21
Output Voltage Select Table A8281SLB
VSEL1 L H VLNB 13 18
+ 100nF Diseq Termination .22uF
Divide by 16
22 Khz Tone Generation
LNB
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ELECTRICAL CHARACTERISTICS at TJ = +125°C, CLNB = 100nF VIN=VINMIN to 47V (unless noted otherwise)
Limits Characteristics Symbol Test Conditions Min. Typ. Max. Units
VIN Supply Voltage Range VINMAX VINMIN Output Voltage VLNB Relative to Voltage Select Table ILOAD = 6mA to 750mA Output Voltage VLNB ENT=H, ILOAD=12mA to 750mA Average Voltage of LNB Logic Input Voltage Vil Vih Logic Input Current Supply current Iih IC C ICCEN Buck Switch On Resistance RDSBUCK Vih=5 V EN = L EN = H, ILOAD = 0 mA TJ = 25 °C, IOUT=750mA TJ =125 °C, IOUT=750mA Buck Switch Current Limit Switching frequency Linear regulator voltage drop Linear Regulator On Resistance IBLIM fo VBUCK RDSLNB fTONE * 16 VSENSE Vo, ENT = L, ILOAD=750mA ILOAD = 750mA, VIN = 18V, TJ = 25 °C Output Select = 18V Tone Characteristics Tone Frequency Tone Amplitude Tone Duty Cycle Tone rise or fall time External Modulation Gain fT O N E A T O NE DCTONE tr, tf gEXTM ENT=H ENT = H, ILOAD = 12mA to 750mA ILOAD = 12mA to 750mA ENT=H, ILOAD = 12mA to 750mA VOUT/VEXTM, f = 22 kHz square wave, ILOAD = 12mA to 750mA EXTM Input Range External Modulation Impedance VEXTM ZEXTM Ac coupled f = 22kHz 100 4 125 10 mVpp k 20 0.4 40 5 4 10 5.0 22 .65 24 0.9 60 15 6 kHz VPP % µs V/V 1 320 700 352 900 .375 2.0 < 1.0 .25 6 .57 .8 10 1 10 .67 .94 2.5 384 1100 0.8 V V µA mA mA A kHz mV -4.5 0 4.5 % 4.5+Vo -4.5 0 4.5 % 47 V
NOTES: 1 . 2.
Typical Data is for design information only. Negative current is defined as coming out of (sourcing) the specified device pin.
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ELECTRICAL CHARACTERISTICS at TJ = +125°C, CLNB = 100nF VIN=VINMIN to 47V (unless noted otherwise)
Limits Characteristics
Protection Circuitry Output Leakage Current Overload flag terminal logic low Output reverse current Current Limiting Threshold Thermal Shutdown Threshold Thermal Shutdown Hysteresis Ioz Vol IO R VOMTH TJ TJ Voh=5.5 V Iol=8 mA EN=L, VLNB= 22 V VIN =22 V or VIN floating 115 < 1.0 0.28 1.0 135 165 20 10 .5 5 155 µa V mA mV °C °C
Symbol
Test Conditions
Min.
Typ.
Max.
Units
NOTES: 1 . 2.
Typical Data is for design information only. Negative current is defined as coming out of (sourcing) the specified device pin.
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Functional Description Buck Regulator. A current-mode buck converter provides the linear regulator a supply voltage that tracks the requested LNB output voltage. The buck converter operates at 16 times the internal tone frequency, nominally 352kHz.
The tracking regulator provides minimum power dissipation across the range of output voltages by adjusting the SENSE pin voltage 900 mV nominally above the LNB output selected. The tracking Regulator also provides adequate headroom for tone injection.
Internal Tone Modulation. The ENT (Tone Enable) terminal activates the internal tone signal modulating the dc output with a 650mV peak to peak, trapezoidal waveform. The internal oscillator is factory trimmed to provide a tone of 22 kHz +/- 2 kHz. No further adjustment is required. Burst coding of the 22 kHz 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. If external modulation is not used, the EXTM terminal should be bypassed to ground via a .1uF ceramic capacitor. The input amplitude should stay within 100 to 125mVpp to guarantee the DiSEqCTM amplitude specification over the output current range.
Linear Regulator. The output linear regulator will sink
and source current. This allows tone modulation into a capacitive load of 100nF for the output current range of 12mA to 750mA.
Slew Rate Control. The programmed output voltage rise and fall times can be set by an internal 25 k resistor and an external capacitor located on the TCAP terminal. The range of acceptable capacitor values is 4.7nF to 47nF. This feature only affects the turn on and programmed voltage rise and fall times. Modulation is unaffected by the choice of TCAP. If LNB output voltage rise and fall time is not a concern, the TCAP terminal should use a 100nF ceramic as a default value to minimize output noise. If a small value capacitor value 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, RSENSE in conjunction with an internal 135mV+/- 20mV reference voltage, VOMTH.
IOM = VOMTH/RSENSE The sense resistor should be chosen based on maximum DC plus AC (tone), load current required, internal VOMTH tolerance, and sense resistor accuracy. For 750mA applications, a precision 140mohm resistor is recommended. For 500mA applications the resistor value can be raised to 200mohms. 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 IOM.
Fault Output. Short-circuit or thermal shutdown will
cause the OLF terminal, an open-drain diagnostic output flag, to go LOW.
Others parts begin by a8
A8-1 A8-2
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