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A829 Datasheet, PDF (1/18 Pages) Allegro MicroSystems – Single LNB Supply and Control Voltage Regulator | |||
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A8294
Single LNB Supply and Control Voltage Regulator
Features and Benefits
âª2-wire serial I2C⢠-compatible interface: control (write) and
status (read)
âªLNB voltages (6 programmable levels) compatible with all
common standards
⪠Tracking switch-mode power converter for lowest dissipation
âªIntegrated converter switches and current sensing
âªProvides up to 700 mA continuous load current
âªOutput current limit of 800 mA minimum, with 48 ms timer
âªStatic current limit circuit allows full current at startup and
13â18 V output transition; reliably starts wide load range
âªPush-pull output stage minimizes 13â18V and 18â13V
output transition times for highly capacitive loads
âªAdjustable rise/fall time via external timing capacitor
âªBuilt-in tone oscillator, factory-trimmed to 22 kHz facilitates
DiSEqC⢠tone encoding, even at no-load
âªTwo methods of 22 kHz tone generation, including outgoing
tone verification (TDET)
âªAuxiliary modulation input
âªLNB overcurrent with timer
âªDiagnostics for output voltage level, input supply UVLO,
and DiSEqCTM tone output
Package: 20-contact 4 Ã 4 mm MLP/QFN (suffix ES)
Description
Intended for analog and digital satellite receivers, this single
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 an LNB down
converter via coaxial cable. The A8294 requires few external
components, with the boost switch 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 levels of component
integration ensure extremely low noise and ripple figures.
The A8294 has been designed for high efficiency, utilizing
the Allegro⢠advanced BCD process. The integrated boost
switch has been optimized to minimize both switching and
static losses. To further enhance efficiency, the voltage drop
across the tracking regulator has been minimized.
For 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.
A comprehensive set of fault registers are provided, which
comply with all the common standards, including: overcurrent,
thermal shutdown, undervoltage, and power not good.
Continued on the next pageâ¦
Functional Block Diagram
L1
33 μH D1
VS
C1
100 nF
C2
100 μF
VIN
C5
C6
100 μF 1 μF
C4
100 nF
LX GNDLX BOOST VCP
VREG
C3
220 nF
Charge
D3
Pump
A
Regulator
Boost
Converter
VDD
R1 R2 R3 R4
DAC
fsw
LNB
Voltage
Control
EXTM
Wave
Shape
Linear
Stage
EXTM
SDA
SCL
ADD
IRQ
I2 Câ¢-
Compatible
Interface
TCAP
Fault Monitor
TGate
fsw
OCP
PNG
TSD
VUV
Clock
Divider 22 kHz
Oscillator
TDO
Tone
Detect
PAD
GND
For recommended external components, refer to table 7
8294-DS, Rev. 5
LNB
D2
C8
100 nF
C10
220 nF
VOUT
D4
C9
10 nF
A
TCAP
C7
22 nF
TDI R8 C10
100 7 10 nF
A D3 and D4 are used for surge protection.
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