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PDF 8282 Data sheet ( Hoja de datos )
| Número de pieza | 8282 | |
| Descripción | (8281) LNB SUPPLY AND CONTROL-VOLTAGE REGULATORS | |
| Fabricantes | Allegro | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de 8282 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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8281 AND
8282
A8282SLB
NC 1
OLF 2
VBULK 3
NC 4
NC 5
GND 6
GND 7
SENSE 8
LNB 99
LX 10 BUCK
VIN 11
REG.
TCAP 12
24 EXTM
23 VINT
22 PUMPX
21 VPUMP
20 CPUMP
19 GND
18 GND
17 ENT
16 EN
15 VSEL0
14 VSEL1
13 LLC
Dwg. PP-072-2
ABSOLUTE MAXIMUM RATINGS
at TA = +25°C
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 ................................. -20°C to +85°C
Junction Temperature, TJ ................ +150°C
Storage Temperature Range,
TS .............................. -55°C to +150°C
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.
FEATURES
s LNB selection and standby function
s Built-in tone oscillator factory trimmed to 22-kHz, facilitates
DiSEqC™ (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)
These devices incorporate features that have patents pending.
Always order by complete part number, e.g., A8282SLB .
1 page  
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 fre-
quency, 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-µF over the output
current range of 12-mA to 750-mA.
Slew rate control. The programmed output volt-
age rise and fall times can be set by an external
capacitor (with an internal 25-kΩ resistor) located on
the TCAP terminal. The range of acceptable capaci-
tor 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 maxi-
mum dc plus ac (tone) load current required, internal
VILNB(th) tolerance, and sense resistor accuracy. For
750-mA applications, a precision 140-mΩ resistor is
recommended. For 500-mA applications, the resistor
value can be raised to 200-mΩ.
In operation, the short-circuit protection produces
current limiting at the input due to the tracking con-
verter. 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 accom-
plished, due to the fast response of the ENT input and
rapid tone response. This allows implementation of
the DiSEqC™ 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 exter-
nal modulation is not used, the EXTM terminal
should be decoupled to ground with a 0.1-µF ceramic
capacitor.
www.allegromicro.com
5
5 Page 
8281 AND 8282
LNB SUPPLY AND
CONTROL-VOLTAGE REGULATORS
Terminal List
A8281SLB A8282SLB
Terminal Terminal Terminal
Name Number Number Terminal Description
NC –
1 No (internal) connection
OLF
VBULK
2
3
2 Overload flag output: low (fault) when ILNB > ILNBM or
TJ > 165°C, high when ILNB < ILNBM and TJ < 130°C
3 Tracking supply voltage to linear regulator
NC
GND
SENSE
LNB
LX
–
4
5
6
7
4, 5 No (internal) connection
6, 7 Ground and substrate
8 Current limit setup resistor
9 Output voltage to LNB
10 Inductor drive point
VIN
TCAP
LLC
VSEL1
8
9
–
10
11 Supply input voltage (minimum, VLNB + 2.5-V)
12 Capacitor for setting the rise and fall time of the outputs for
line-length compensation
13 Logic input: output voltage select
14 Logic input: output voltage select
VSEL0
EN
–
11
15 Logic input: output voltage select
16 Logic input: when high, enables device
ENT
12
17 Logic input: when high, enables internal 22-kHz modulation
GND
CPUMP
13
14
18, 19
20
Ground and substrate
High side of charge-pump capacitor
VPUMP
PUMPX
VINT
EXTM
15
16
–
1
21 Gate-supply voltage for high-side drivers
22 Charge-pump drive
23 Bypass capacitor for internal voltage reference
24 External modulation input
www.allegromicro.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet 8282.PDF ] | |
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