A8294 Datasheet, PDF (1/18 Pages) Allegro MicroSystems – Single LNB Supply and Control Voltage Regulator

A8294
Single LNB Supply and Control Voltage Regulator
Features and Benefits
▪2-wire serial I²C™ -compatible interface: control (write) and
status (read)
▪LNB voltages (6 programmable levels) compatible with all
common standards
▪ Tracking switch-mode power converter for lowest dissipation
▪Integrated converter switches and current sensing
▪Provides up to 700 mA continuous load current
▪Output current limit of 800 mA minimum, 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→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
▪Two methods of 22 kHz tone generation, including outgoing
tone verification (TDET)
▪Auxiliary modulation input
▪LNB overcurrent with timer
▪Diagnostics for output voltage level, input supply UVLO,
and DiSEqC^TM tone output
Package: ^{20-contact 4 × 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 page…
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 C™-
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.