Document
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.
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5 mm × 5 mm (Not to scale)
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.
Functional Block Diagram
C2 100 µF
A
Channel 1 L1 33 µH
L3
D1
1 µH
A8286
C5 100 µF
C6 1 µF
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
TMode1 EXTM1 Fsw
DAC
LNB Voltage Control
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 15 Ω
LNB1 C8
D2 220 nF
L2 220 µH
R8 30 Ω
C9 220 nF
D
TCAP1 C7 22 nF
C11 0.68 µF
B
TDI1 R7 100 Ω
C10 10 nF
D3 C
VOUT1
C13
D4
10 nF
C
8286-DS, Rev. 22 MCO-0000208
January 27, 2020
A8286
Dual LNB Supply and Control Voltage Regulator
Description (continued) A comprehensive set of fault registers are provided which, comply with all the common standards, including: overcurrent, thermal shutdown, undervoltage, cable disconnect, power not good, and tone detect.
The device uses a 2-wire bidirectional serial interface, compatible with the I2C™ standard, that operates up to 400 kHz.
The A8286 is supplied in a lead (Pb) free 28-lead MLP/QFN with 100% matte tin leadframe.
Absolute Maximum Ratings
Characteristic
Symbol
Conditions
Rating
Units
Load Supply Voltage, VIN pin
VIN
Output Current1
IOUT
30
V
Internally Limited
A
Output Voltage, BOOST pin Output Voltage, LNB pin Output Voltage, LX pin Output Voltage, VCP pin Logic Input Voltage, EXTM pin
Surge2 VCP
–0.3 to 33
V
–1 to 33
V
–0.3 to 30
V
–0.3 to 41
V
–0.3 to 5
V
Logic Input Voltage, other pins
–0.3 to 7
V
Logic Output Voltage
–0.3 to 7
V
Operating Ambient Temperature
TA
–20 to 85
°C
Junction Temperature
TJ(max)
150
°C
Storage Temperature
Tstg
–55 to 150
°C
1Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the specified current ratings, or a junction temperature, TJ, of 150°C. 2Use Allegro recommended Application circuit.
Package Thermal Characteristics*
Package
RθJA (°C/W)
PCB
ET
32
4-layer
* Additional information is available on the Allegro website.
Ordering Information Use the following complete part numbers when ordering:
Part Number
Packinga
A8286SETTR-Tb
7-in. reel.