8283
PRELIMINARY INFORMATION
(Subject to change without notice)
October 9, 2001
LNB SUPPLY AND
CONTROL-VOLTAGE REGULATOR
Intended for analog and digital satellite receivers, the low-noise block
converter regulator (LNBR) is a monolithic linear and switching voltage
regulator designed to provide power and interface signals to the LNB down
converter via the coaxial cable. If the device is in stand-by mode (EN terminal
LOW), the regulator output is disabled, allowing the antenna downconverters to
be supplied or controlled by other satellite receivers sharing the same coaxial
cable. Similar two-output LNB supply and control voltage regulators are the
A8284SB/SLB.
For slave operation in single-dish dual-receiver systems, the bypass
function is implemented by an electronic switch between the master input
terminal (MI) and the LNB terminal, leaving all LNB power and control
functions to the master receiver. This electronic switch is closed if the device
is powered, EN is HIGH, and OSEL is LOW.
The regulator outputs are 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 compen-
sate for the voltage drop in the coaxial cable (LLC terminal HIGH). The
LNBR combines a tracking switching regulator and low-noise linear regulator.
Logic inputs (V
SEL0
, V
SEL1
, and LLC) select the desired output voltage. A
tracking current-mode buck converter provides the linear regulator with an
input voltage that is set to the output voltage plus typically 0.8 V. This main-
tains constant voltage drop across the linear regulator while permitting ad-
equate voltage range for tone injection.
The device is supplied in a 24-pin plastic DIP with batwing tabs
(A8283SB), or a 24-lead SOIC power-tab package (A8283SLB). In both cases,
the power tab is at ground potential and needs no electrical isolation.
Data Sheet
27448.1
A8283SLB
OSEL
OLF
VBULK
MIOUT
MI
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
4
5
6
7
8
9
9
10
11
12
BUCK
REG.
CHARGE
PUMP
VOLTAGE
CONTROL
21
20
19
18
17
16
15
14
13
Dwg. PP-072A
Note that the A8283SB (dual in-line package)
and A8283SLB (small-outline IC package) are
electrically identical and share a common
terminal number assignment.
FEATURES
s
s
s
s
s
s
s
s
s
s
Short-Circuit Protected Bypass Function for Slave Operation
LNB Selection and Stand-By Function
Built-In Tone Oscillator Factory Trimmed to 22 kHz, Facilitates
DiSEqC™ (a trademark of EUTELSAT) Encoding
Full Modulation With No Load
Tracking Switch-Mode Power Converter for Lowest Dissipation
Externally Adjustable Short-Circuit Protection
LNB Short-Circuit Protection and Diagnostics
Auxiliary Modulation Input
Cable Length Compensation
Internal Over-Temperature Protection
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
IN
..........................
47 V
Output Current, I
O
............................
1.0 A
Logic Input Voltage Range,
V
I
...................................
-0.5 V to +7 V
Bypass Switch Current,
I
SW
........................
Internally Limited
Flag Output Voltage, V
OLF
..................
7 V
Operating Temperature Range,
T
A
...............................
-20
°
C to +85
°
C
Storage Temperature Range,
T
S
.............................
-40
°
C to +150
°
C
This device incorporates features that have patents pending.
Always order by complete part number, e.g.,
A8283SLB
.
8283
LNB SUPPLY AND
CONTROL-VOLTAGE REGULATOR
FUNCTIONAL BLOCK DIAGRAM
R
S
SENSE
V
BULK
PUMPX
C
PUMP
V
PUMP
47 V
MAX
V
IN
LX
+
MI
V
INT
VOLTAGE
REG.
BOOST
VOLTAGE
MI
OUT
0
1
–
5V
176 kHz
+
352 kHz
25 kΩ
–
+
7V
VREF
BUCK
CONV.
–
+
OVER-
CURRENT
–
+
800 mV
+
150 mV
CHARGE
PUMP
EN
÷2
ENT
÷8
&
WAVESHAPING
22 kHz TONE
TSD
OLF
OVER-
CURRENT
5 kΩ
1 kΩ
R
EXTM
OSEL
V
SEL0
V
SEL1
LLC
TCAP
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
V
LNB(typ)
13 V
14 V
18 V
19 V
12 V
13 V
20 V
21 V
2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 2001 Allegro MicroSystems, Inc.
–
LNB
5 kΩ
EXTM
Dwg. FP-051-1
8283
LNB SUPPLY AND
CONTROL-VOLTAGE REGULATOR
ELECTRICAL CHARACTERISTICS at T
A
= 25
°
C, ENT = L, EN = H, OSEL = H, LLC = L, V
IN
= 24 V,
V
O
= 13 V or 18 V, I
O
= 50 mA, R
EXTM
= open (unless otherwise noted).
Limits
Characteristic
Supply Voltage
Output Voltage
Symbol
V
IN
V
O
Test Conditions
I
O
= 600 mA, VSEL0 = L, VSEL1 = L, LLC = L
I
O
= 600 mA, VSEL0 = L, VSEL1 = L, LLC = L
I
O
= 600 mA, VSEL0 = L, VSEL1 = L, LLC = H
I
O
= 600 mA, VSEL0 = L, VSEL1 = H, LLC = L
I
O
= 600 mA, VSEL0 = L, VSEL1 = H, LLC = H
I
O
= 600 mA, VSEL0 = H, VSEL1 = L, LLC = L
I
O
= 600 mA, VSEL0 = H, VSEL1 = L, LLC = H
I
O
= 600 mA, VSEL0 = H, VSEL1 = H, LLC = L
I
O
= 600 mA, VSEL0 = H, VSEL1 = H, LLC = H
Load Regulation
Current-Limiting Threshold
Tone Frequency
Tone Amplitude
External Modulation
Output
Tone Duty Cycle
Tone Rise or Fall Time
External Modulation Gain
External Modulation
Input Voltage
External Modulation
Impedance
∆V
O
V
OM(th)
f
tone
V
tone(PP)
V
mod(out)
dc
tone
t
r
, t
f
G
mod
V
mod(PP)
Z
mod
ENT = H
ENT = H
ENT = L, I
O
= 600 mA, R
EXTM
= 200 kΩ,
V
mod(PP)
= 130 mV, f = 22 kHz
ENT = H
ENT = H
∆V
O
/∆V
mod
, f = 22 kHz
AC coupling
4.4
I
O
= 50 to 600 mA
125
20
550
400
Min.
4.5 + V
O
12.5
13.4
17.3
18.2
11.5
12.5
19.2
20.2
13
14
18
19
12
13
20
21
80
135
22
680
Typ.
Max.
47
13.8
14.9
18.7
19.8
12.8
13.8
20.8
21.8
220
160
24
800
800
Units
V
V
V
V
V
V
V
V
V
mV
mV
kHz
mV
mV
50
10
4.9
5.6
160
%
µs
V/V
mV
f = 22 kHz
5.0
kΩ
continued next page ...
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3
8283
LNB SUPPLY AND
CONTROL-VOLTAGE REGULATOR
ELECTRICAL CHARACTERISTICS at T
A
= 25
°
C, ENT = L, EN = H, OSEL = H, LLC = L, V
IN
= 24 V,
V
O
= 13 V or 18 V, I
O
= 50 mA, R
EXTM
= open (unless otherwise noted).
Limits
Characteristic
Overload Flag Logic Low
Overload Flag Leakage Current
Logic Input Voltage
Symbol
V
OL
I
OZ
V
IL
V
IH
Logic Input Current
I
IL
I
IH
Supply Current
I
IN
V
IL
= 0 V
V
IH
= 5 V
Outputs disabled (EN = L)
ENT = H, I
O
= 600 mA, V
O
= 13 V
Thermal Shutdown Temp.
Linear Regulator Voltage Drop
Switching Frequency
Bypass Switch Current Limit
Bypass Switch Voltage Drop
(MI to LNB)
T
J
∆V
BUCK
f
O
I
swM
V
sw
V
BULK
— V
O
16 x f
tone
OSEL = L
OSEL = L, I
sw
= 300 mA
320
400
2.0
<-1.0
<1.0
0.5
382
165
0.8
352
900
0.15
384
-10
10
Test Conditions
I
OL
= 8 mA
V
OH
= 5.5 V
Min.
Typ.
0.28
<1.0
Max.
0.8
10
0.8
Units
V
µA
V
V
µA
µA
mA
mA
°C
V
kHz
mA
V
FUNCTIONAL DESCRIPTION
The ENT (Tone Enable) terminal activates the internal
tone signal, modulating the dc output with a
±0.3
V,
22 kHz symmetrical waveform. The internal oscillator is
factory-trimmed to provide a tone of 22 kHz
±2
kHz. No
further adjustment is required. The internal oscillator
operates the buck converter at 16 times the tone fre-
quency.
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 DiSEqC™
protocols.
To improve design flexibility and to allow implemen-
tation 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 termi-
nal. If external modulation is not used, the EXTM termi-
nal can be left open.
Applications that are required to deliver more than
400 mA and use the external modulation terminal should
be rebiased to increase the voltage drop across the linear
regulator. This will allow full modulation under all
conditions.
4
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
8283
LNB SUPPLY AND
CONTROL-VOLTAGE REGULATOR
FUNCTIONAL DESCRIPTION (cont’d)
This can be accomplished by connecting a 200 kΩ
resistor from the external modulation terminal (24) to
ground. This will reduce the LNB output voltage by
typically 300 mV without effecting the V
BULK
voltage.
The output voltage can be restored to the programmed
value by connecting a 1 MΩ resistor from the V
INT
terminal (23) to the T
CAP
terminal (12). This raises both
V
BULK
and V
O
by typically 300 mV.
The output linear regulator will sink and source
current. This feature allows full modulation capability
into capacitive loads as high as 0.25
µF.
The programmed output voltage rise and fall times
can be set by an internal 25 kΩ resistor and an external
capacitor located on the TCAP terminal. Although any
value of capacitor is permitted, practical values are
typically 0.001
µF
to 0.02
µF.
This feature only affects
the turn on and programmed voltage rise and fall times.
Modulation is unaffected by the choice of TCAP. This
terminal can be left open if voltage rise and fall time
control is not required.
Two terminals are dedicated to the over-current
protection/monitoring: SENSE and OLF. The LNB output
is current limited. The short-circuit protection threshold is
set by the value of an external resistor, R
S
, between
terminals 3 and 8. R
S
= V
OM(th)
/I
OM
where V
OM(th)
is the
current-limiting threshold voltage and I
OM
is the desired
current limit value. The minimum recommended value
for R
S
is 0.15
Ω.
In operation, the short-circuit protection produces
current fold-back at the input due to the tracking con-
verter. If the output is shorted, the linear regulator will
limit the output current to I
OM
. The tracking converter
will maintain a constant voltage drop of 0.8 V across the
linear regulator. This condition results in typically
550 mW dissipation (I
OM
x 0.8 V). Short-circuit or
thermal-shutdown activation will cause the OLF terminal,
an open-drain diagnostic output flag, to go LOW.
Thermal resistance:
DIP
—
R
θJA
= 40
°
C/W, R
θJT
= 6
°
C/W, or
SOIC —
R
θJA
= 55
°
C/W, R
θJT
= 6
°
C/W.
The device junction temperature should be kept below
150°C. Thermal shut-down circuitry turns off the device
if junction temperature exceeds +165°C typically.
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 responsi-
bility 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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