Voltage Regulator. A8291 Datasheet

A8291 Regulator. Datasheet pdf. Equivalent

Part A8291
Description Single LNB Supply and Control Voltage Regulator
Feature www.DataSheet4U.com A8291 Single LNB Supply and Control Voltage Regulator Features and Benefits ▪ 2.
Manufacture Allegro MicroSystems
Datasheet
Download A8291 Datasheet



A8291
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A8291
Single 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
Provides up to 500 mA load current
Static current limit circuit allows full current at startup and
1318V output transition; reliably starts wide load range
Push-pull output stage minimizes 1318V and 1813V
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
Filter bypass MOSFET minimizes losses during tone transmit
22 kHz tone detector facilitates DiSEqC™ 2.0 decoding
Auxiliary modulation input
LNB overcurrent with timer
Diagnostics for output voltage level, input supply UVLO,
and DiSEqC™ tone output
Cable disconnect diagnostic
Package:
28 pin 5 mm × 5mm MLP/QFN
(suffix ET)
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 A8291 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 A8291 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.
The A8291 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
Continued on the next page…
VS
VREG
C3
220 nF
VDD
R1 R2 R3 R4 R5 R6
EXTM
BFC
TDO
SDA
SCL
ADD
IRQ
8291-DS, Rev.3
C1
100 nF
Regulator
DAC
I2 C™-
Compatible
Interface
Functional Block Diagram
L1
33 μH
D1
L3
1 MH
C2
100 μF
VIN
C5
100 μF
LX GNDLX
C6
1 μF
C4
100 nF
BOOST VCP
Charge BFC
Pump
R10 B
17
Boost
Converter
VPump
fsw
LNB
Voltage
Control
EXTM
TMode
Wave
Shape
Linear
Stage
TCAP
Fault Monitor
TGate
fsw
OCP
PNG
TSD
VUV
Clock
Divider 22 kHz
Oscillator
D2
B
BFO
BFI
C12 C
R7
15 7
LNB
C8
D3 220 nF
TCAP
C7
10 nF
L2
220 μH
R9
30 7
C11
0.68 μF
A
PAD GND
TDO
Tone
Detect
TDI R8
100 7
C10
10 nF
D5
B
VOUT
C13
10 nF
C9
220 nF
C
D4
B
A
R9-C11 network is needed only when a highly
inductive load is applied, such as ProBand LNB.
B D2, D4, D5, and R10 are used for surge protection.
C Either C12 or C9 should be used, but not both.



A8291
A8291
Single LNB Supply and Control Voltage Regulator
Description (continued)
time source. A DiSEqC™ filter bypass switch is also integrated, to
minimize the output impedance during tone generation.
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 A8291 is supplied in a lead (Pb) free 28-lead MLP/QFN.
Selection Guide
Part Number
Packinga
A8291SETTR-Tb
7 in. reel, 1500 pieces/reel
12 mm carrier tape
aContact Allegro for additional packing options.
bLeadframe plating 100% matte tin.
Description
ET package, MLP/QFN surface mount
0.90 mm nominal height
Absolute Maximum Ratings
Characteristic
Symbol
Conditions
Rating
Units
Load Supply Voltage, VIN pin
Output Current*
Output Voltage; BFI, BFO, LNB, LX, and
BOOST pins
VIN
IOUT
16
Internally
Limited
–1 to 33
V
A
V
Output Voltage, VCP pin
–1 to 41
V
Logic Input Voltage, EXTM and BFC pins
–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
*Output 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.
Package Thermal Characteristics*
Package
RθJA
(°C/W)
PCB
ET 32
4-layer
* Additional information is available on the Allegro website.
Allegro MicroSystems, Inc.
2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com





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