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A8287SLB

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18
Description
Intended for analog and digital satellite receivers, the LNB
(low noise block) converter regulator is a monolithic linear and
switching voltage regulator, specifically designed to provide
power and interface signals to an LNB downconverter, via
coaxial cable.
The device uses a 2-wire bidirectional serial interface,
compatible with the I
2
C (Inter-C bus) standard, that operates
up to 400 kHz.
The A8285 is supplied in a 16-lead plastic power SOIC with
internally fused leads for thermal dissipation. The A8287 is
supplied in a 24-lead plastic power SOIC with internally fused
leads. Both devices are also available in lead (Pb) free versions,
with 100% matte tine leadframe plating.
A8285-DS, Rev. F
Features and Benefits
• LNB selection and standby function
• Provides up to 500 mA load current
• Two-wire serial I
2
C interface
• Built-in tone oscillator, factory-trimmed to 22 kHz;
facilitates DiSEqC™ 2.0 encoding
• Auxiliary modulation input
• 22 kHz tone detector facilitates DiSEqC™ decoding
(A8287 only)
• Tracking switch-mode power converter for lowest
dissipation
• LNB overcurrent protection and diagnostics
• Internal overtemperature protection
• LNB voltages (16 possible levels) compatible with all
common standards
LNB Supply and Control Voltage Regulator
Packages
Functional Block Diagram
A8285 and A8287
16-pin SOIC
(A8285)
24-pin SOIC
(A8287)
22 kHz Tone
Detector
Internal
Regulator
Boost Converter
Charge
Pump
Clock
Divider
22 kHz
Ton e
Generator
Output
Voltage
Select
Fault Monitor
Overcurrent
TSD
Undervoltage
VREG
BOOST
Feedback
33 µH
33 µF
EXTM
V
IN
SDA
SCL
ADD
IRQ
100 mV
VIN
LX
100 nF
VCP
BOOST
OSC In
DISABLE
100 nF
LNB
220 Ω
6.8 nF
33 µH
220 nF
1.5 µF
TCAP
TOUT
TDI
10 nF
V
DD
TDO
V
DD
OSC
Overcurrent
VPUMP
220 nF
Overcurrent
15 Ω
100 µF
100 nF
C10 C1
L1 D1
C5 C2 C4
C3
R3 R4 R5
R6
C9
R2
C8
D2
C6
C7
L2
R1
Tracking
Regulator
GM
LNB Supply and Control Voltage Regulator
A8285 and
A8287
2
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Absolute Maximum Ratings
Characteristic Symbol Notes Rating Unit
Load Supply Voltage V
IN
16 V
Output Current I
OUT
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 rating or a junction tempera-
ture of +150°C
Internally Limited –
Output Voltage –
LNB, BOOST –0.3 to 28 V
TOUT –0.3 to 22 V
Logic Input –
EXTM –0.3 to 5 V
Other –0.3 to 7 V
Logic Output – –0.3 to 7 V
Package Power DIssipation –
See power dis sipation information in the Application
Information section
––
Operating Temperature
Ambient T
A
–20 to 85 ºC
Junction T
J
–20 to 150 ºC
Storage T
S
–55 to 150 ºC
Part Number Pb-free Package Description
A8285SLB – 16-pin SOIC Tone detect not provided
A8285SLB-T Yes 16-pin SOIC Tone detect not provided
A8287SLB – 24-pin SOIC All features
A8287SLB-T Yes 24-pin SOIC All features
Selection Guide
LNB Supply and Control Voltage Regulator
A8285 and
A8287
3
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
ID Characteristics Suggested Manufacturer
C1 33 F, 25 V, esr < 200 m, I
ripple
> 350 mA Nichicon, part number UHC1E330MET
C2, C5,C10 100 nF, 50 V, X5R or X7R
C4 100 F, 35 V, esr < 75 m, I
ripple
> 800 mA Nichicon, part number UHC1V101MPT
C3,C6 220 nF, 50 V, X5R or X7R
C7 1.5 F, 50 V, X5R or X7R
C8 6.8 nF, 50 V; Y5V, X5R, or X7R
C9 10 nF (maximum), 50 V; Y5V, X5R, or X7R
R1
15 , 1%, c W
R2
220 , 1%, 2 W
R3-R6 Value determined by V
DD
, bus capacitance. etc.
L1 33 H, I
DC
> 1.3 A TDK, part number TSL0808-330K1R4
L2 33 H, I
DC
> 0.5 A TDK, part number TSL0808-330K1R4
D1 1 A, 35 V or 40 V, Schottky diode Various, part number 1N5819; Sanken, part number AW04
D2 1 A, 100 V, 1N4002
Tone detector and leads TDI and TDO are not provided in 16-pin package (A8285).
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18

A8287SLB

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Description:
IC REG CONV RECVRS 1OUT 24SOIC
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