8284 Datasheet, PDF (1/8 Pages) Allegro MicroSystems – TWO-OUTPUT LNB SUPPLY AND CONTROL-VOLTAGE REGULATOR

8284
ADVANCE INFORMATION
(Subject to change without notice)
December 22, 2000
TWO-OUTPUT LNB SUPPLY AND
CONTROL-VOLTAGE REGULATOR
Intended for analog and digital satellite receivers, the low noise block
A8284SLB
converter regulator (LNBR) is a monolithic linear and switching voltage
regulator designed to provide power and interface signals to the LNB
OSEL 1
24 EXTM
downconverter via the coaxial cable. Because most satellite receivers have two
antenna ports, the output voltage of the regulator is available at one of two
OLF 2
23 VINT
logic-selectable output terminals (LNBA, LNBB). If the device is in stand-by
mode (EN terminal LOW), both regulator outputs are disabled, allowing the
VBULK 3
22 PUMPX
antenna downconverters to be supplied and controlled by other satellite
CONTACT ^{FACTORY LNBB 4}
NC 5
GND 6
GND 7
SENSE 8
LNBA 99
LX 10 BUCK
VIN 11
TCAP 12
REG.
21 VPUMP
20 CPUMP
19 GND
18 GND
17 ENT
16 EN
15 VSEL0
14 VSEL1
13 LLC
Dwg. PP-072-1A
Note that the A8284SB (dual in-line package)
and A8284SLB (small-outline IC package) are
electrically identical and share a common
terminal number assignment.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V_IN .......................... 47 V
Output Current, I_O .... Internally Limited
Logic Input Voltage Range,
receivers sharing the same coaxial cable. Similar single-output devices, with a
bypass function for slave operation in single-dish dual-receiver systems, are the
A8283SB/SLB.
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
regulators. Logic inputs (VSEL0, VSEL1, and LLC) select the desired output
voltage. A tracking current-mode buck converter provides the linear regulator
input voltage that is set to the output voltage plus typically 0.8 V. This
maintains constant voltage drop across the linear regulators while permitting
adequate voltage range for tone injection.
The device is supplied in a 24-pin plastic DIP with batwing tabs
(A8284SB), or a 24-lead SOIC power-tab package (A8284SLB). In both cases,
the power tab is at ground potential and needs no electrical isolation.
FEATURES
I Complete Interface for Two LNBs Remote Supply and Control
I LNB Selection and Stand-By Function
I Built-In Tone Oscillator Factory Trimmed to 22 kHz, Facilitates
DiSEqC™ (a trademark of EUTELSAT) Encoding
I Full Modulation With No Load
I Tracking Switch-Mode Power Converter for Lowest Dissipation
I Externally Adjustable Short-Circuit Protection
I LNB Short-Circuit Protection and Diagnostics
I Auxiliary Modulation Input
I Cable Length Compensation
I Internal Over-Temperature Protection
V_I ................................... -0.5 V to +7 V
Flag Output Voltage, V_OLF .................. 7 V
This device incorporates features that have patents pending.
Operating Temperature Range,
T_A ............................... -20°C to +85°C
Storage Temperature Range,
T_S ............................. -40°C to +150°C
Always order by complete part number, e.g., A8284SLB .