A8292
Dual LNB Supply and Control Voltage Regulator
Features and Benefits
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2-wire serial I
2
C™ -compatible interface: control (write) and
status (read)
LNB voltages (16 programmable levels) compatible with
all common standards
Tracking switch-mode power converter for lowest dissipation
Integrated converter switches and current sensing
Provides up to 500 mA per channel and 750 mA total
Static current limit circuit allows full current at startup and
13
→
18 V output transition; reliably starts wide load range
Push-pull output stage minimizes 13
→
18 V and 18
→
13 V
output transition times for highly capacitive loads
Adjustable rise/fall time via external timing capacitor
Built-in tone oscillator, factory-trimmed to 22 kHz
facilitates DiSEqC™ tone encoding, even at no-load
Four methods of 22 kHz tone generation, via I
2
C™ data
bits and/or external pin
22 kHz tone detector facilitates DiSEqC™ 2.0 decoding
Auxiliary modulation input
LNB overcurrent with timer
Diagnostics for output voltage level, input supply UVLO,
and DiSEqC™ tone output
Cable disconnect diagnostic
Description
Intended for analog and digital satellite receivers, this dual
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 two LNB down
converters via coaxial cables. The A8292 requires few external
components, with the boost switches and compensation circuitry
integrated inside of the device. A high switching frequency is
chosen to minimize the size of the passive filtering components,
further assisting in cost reduction. The high level of component
integration ensures extremely low noise and ripple figures.
The A8292 has been designed for high efficiency, utilizing
the Allegro® advanced BCD process. The integrated boost
switches have been optimized to minimize both switching and
static losses. To further enhance efficiency, the voltage drop
across the tracking regulators has been minimized.
The A8292 has integrated tone detection capability, to support
full two-way DiSEqC™ communications. Several schemes
are available for generating tone signals, all the way down
to no-load, and using either the internal clock or an external
time source.
Package:
28 pin 5 mm × 5mm MLP/QFN
(suffix ET)
Continued on the next page…
Functional Block Diagram
V
S
A
C2
100
μF
Channel 1
L1
33
μH
D1
L3
1 H
V
DD
R4
R5
C5
100
μF
C6
1
μF
C4
100 nF
VCP1
D3
C
TDO1 EXTM1
A8292
LX1
GNDLX1
BOOST1
Charge
Pump
VIN
C1
100 nF
VREG
C3
220 nF
DAC
R2
R1
SDA
SCL
I
2
C–
Compatible
Interface
Fault Monitor
OCP1
OCP2
PNG1
PNG2
TSD
VUV
Fsw
TCAP1
Clock
Divider 22 kHz
Oscillator
TDO1
Tone
Detect
TDI1
C7
10 nF
R3
Boost
Converter
Regulator
Fsw
LNB
Voltage
Control
C12
D
TMode1
EXTM1
VPump
R6
15
LNB1
C8
D2 220 nF
R8
30
C11
0.68
μF
B
Wave
Shape
TCAP1
TGate1
Linear
Stage
V
OUT1
L2
220
μH
C9
220 nF
D
C13
10 nF
D4
C
A
B
C
D
Channel 1 of 2 channels shown.
R8-C11 network is needed only when high
inductive load is applied, such as ProBrand LNB.
D3 and D4 are used for surge protection.
Either C12 or C9 should be used, but not both.
IRQ
R7
100
C10
10 nF
PAD
GND
8292-DS, Rev. 3
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
