A8286
Dual LNB Supply and Control Voltage Regulator
Features and Benefits
Description
▪ 2-wire serial I2C™ -compatible interface: control (write)
and status (read)
Intended for analog and digital satellite receivers, this dual
low-noise block converter regulator (LNBR) is a monolithic
linearandswitchingvoltageregulator, specificallydesignedto
provide the power and the interface signals to two LNB down
convertersviacoaxialcables.TheA8286requiresfewexternal
components,withtheboostswitchesandcompensationcircuitry
integrated inside of the device. A high switching frequency is
chosentominimizethesizeofthepassivefilteringcomponents,
furtherassistingincostreduction.Thehighlevelofcomponent
integration ensures extremely low noise and ripple figures.
▪ 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 650 mA per channel and 1.0 A total
continuous load current
▪ Provides up to 700 mA per channel and 1.1 A total for 2000 ms
▪ Output current limit of 900 mA typical, with 48 ms timer
▪ Static current limit circuit allows full current at startup and
13→18V output transition; reliably starts wide load range
▪ Push-pull output stage minimizes 13→18V and 18→13V
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 I2C™ data
bits and/or external pin
The A8286 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.
TheA8286 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.
▪ 22 kHz tone detector facilitates DiSEqC™ 2.0 decoding
▪ Auxiliary modulation input
▪ LNB overcurrent with timer
▪ Provides VOUT within 19 to 21 VDC at 700 mA for
SWM (single wire multiswitch) operation
▪ Diagnostics for output voltage level, input supply UVLO,
and DiSEqC™ tone output
▪ Cable disconnect diagnostic
Continued on the next page…
Package:
28 pin 5 mm × 5mm
QFN/MLP (suffix ET)
Functional Block Diagram
V
S
A
C2
100 MF
Channel 1
L1
33 MH
L3
1 MH
D1
V
DD
C6
C5
C4
100 nF
1 MF
100 MF
R4
TDO1 EXTM1
R5
LX1
GNDLX1
BOOST1 VCP1
A
B
D3
C
A8286
Channel 1 of 2 channels shown.
R8-C11 network is needed only when high
inductive load is applied, such as ProBrand LNB.
Charge
Pump
C12
D
VIN
Boost
Converter
C
D
D3 and D4 are used for surge protection.
C1
100 nF
Either C12 or C9 should be used, but not both.
VREG
TMode1
EXTM1
R6
15 7
Regulator
VPump
C3
Fsw
220nF
LNB
Voltage
Control
V
OUT1
LNB1
Wave
Shape
Linear
Stage
DAC
L2
220 MH
C8
220 nF
R3
TCAP1
D2
R2
C9
D4
C
TGate1
C13
10 nF
R1
220 nF
R8
30
7
D
SDA
SCL
Fsw
Fault Monitor
TCAP1
C11
0.68
OCP1
OCP2
PNG1
PNG2
TSD
M
F
Clock
Divider
2
Cꢀ
Compatible
Interface
I
22 kHz
C7
10 nF
B
Oscillator
TDO1
VUV
TDI1
Tone
Detect
IRQ
R7
100 7
C10
10 nF
PAD
GND
8286-DS, Rev. 3