A8286 Datasheet, PDF (1/20 Pages) Allegro MicroSystems – Dual LNB Supply and Control Voltage Regulator

A8286
Dual LNB Supply and Control Voltage Regulator
Features and Benefits
▪ 2-wire serial I²C™ -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
▪ Output current limit of 900 mA typical, with 48 ms timer
▪ 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 I²C™ data
bits and/or external pin
▪ 22 kHz tone detector facilitates DiSEqC™ 2.0 decoding
▪ Diagnostics for output voltage level, input supply UVLO,
and DiSEqC™ tone output
▪ Cable disconnect diagnostic
▪ Auxiliary modulation input
▪ LNB overcurrent with timer
Package: 28-pin QFN (suffix ET)
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 A8286 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 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.
The A8286 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.
Continued on the next page…
5 mm × 5 mm
(Not to scale)
Functional Block Diagram
VS
VDD
A _{Channel 1 of 2 channels shown.}
B R8-C11 network is needed only when high
inductive load is applied, such as ProBrand LNB.
C D3 and D4 are used for surge protection.
D Either C12 or C9 should be used, but not both.
C2
100 MF
A
Channel 1 _L1
33 MH
L3
D1
1 MH
A8286
C5
100 MF
C6
1 MF
R4
R5
C4
100 nF
TDO1 EXTM1
LX1 GNDLX1
BOOST1 VCP1
VIN
C1
100 nF
VREG
C3
220 nF
Regulator
R3
R2
R1
SDA
SCL
I² C
Compatible
Interface
IRQ
Boost
Converter
Charge
Pump
C12 D
Fsw
DAC
LNB
Voltage
Control
TMode1
EXTM1
Wave
Shape
TCAP1
TGate1
Fault Monitor
OCP1
OCP2
PNG1
PNG2
TSD
VUV
Fsw
Clock
Divider 22 kHz
Oscillator
PAD
GND
VPump
Linear
Stage
TDO1
Tone
Detect
R6
157
LNB1
C8
D2 220 nF
L2
220 MH
R8
30 7
C9
220 nF
D
TCAP1
C7
22 nF
C11
0.68 MF
B
TDI1
R7
100 7
C10
10 nF
D3
C
VOUT1
D4
C13
10 nF
C
8286-DS, Rev. 17