A8285 and A8287
LNB Supply and Control Voltage Regulator
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
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.
Packages
16-pin SOIC
(A8285)
24-pin SOIC
(A8287)
Functional Block Diagram
V
IN
C10
100 nF
C1
33 µF
L1
33 µH
D1
C5
100 nF
C2
100 nF
C4
100 µF
VIN
VREG
C3
220 nF
Internal
Regulator
OSC In
Boost Converter
LX
VCP
BOOST
BOOST
Feedback
Charge
Pump
VPUMP
Overcurrent
OSC
EXTM
100 mV
DISABLE
R1
15
Ω
L2
33 µH
1.5 µF
C7
220 nF
C6
R3 R4 R5
V
DD
SDA
SCL
ADD
Clock
Divider
22 kHz
Tone
Generator
LNB
Tracking
Regulator
D2
TCAP
Output
Voltage
Select
GM
TOUT
TDI
6.8 nF
C8
220
Ω
R2
10 nF
C9
R6
TDO
V
DD
IRQ
Fault Monitor
Overcurrent
TSD
Undervoltage
Overcurrent
22 kHz Tone
Detector
A8285-DS, Rev. F
A8285 and
A8287
LNB Supply and Control Voltage Regulator
Selection Guide
Part Number
A8285SLB
A8285SLB-T
A8287SLB
A8287SLB-T
Pb-free
–
Yes
–
Yes
Package
16-pin SOIC
16-pin SOIC
24-pin SOIC
24-pin SOIC
Description
Tone detect not provided
Tone detect not provided
All features
All features
Absolute Maximum Ratings
Characteristic
Load Supply Voltage
Symbol
V
IN
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
LNB, BOOST
TOUT
EXTM
Other
See power dissipation information in the Application
Information section
Notes
Rating
16
Unit
V
Output Current
I
OUT
Internally Limited
–
Output Voltage
Logic Input
Logic Output
Package Power DIssipation
Operating Temperature
Ambient
Junction
Storage
–
–
–
–
–0.3 to 28
–0.3 to 22
–0.3 to 5
–0.3 to 7
–0.3 to 7
–
V
V
V
V
V
–
T
A
T
J
T
S
–20 to 85
–20 to 150
–55 to 150
ºC
ºC
ºC
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A8285 and
A8287
LNB Supply and Control Voltage Regulator
Tone detector and leads TDI and TDO are not provided in 16-pin package (A8285).
ID
C1
C2, C5,C10
C4
C3,C6
C7
C8
C9
R1
R2
R3-R6
L1
L2
D1
D2
Characteristics
33
μF,
25 V, esr < 200 mΩ, I
ripple
> 350 mA
100 nF, 50 V, X5R or X7R
100
μF,
35 V, esr < 75 mΩ, I
ripple
> 800 mA
220 nF, 50 V, X5R or X7R
1.5
μF,
50 V, X5R or X7R
6.8 nF, 50 V; Y5V, X5R, or X7R
10 nF (maximum), 50 V; Y5V, X5R, or X7R
15
,
1%,
c
W
220
,
1%,
2
W
Value determined by V
DD
, bus capacitance. etc.
33
μH,
I
DC
> 1.3 A
33
μH,
I
DC
> 0.5 A
1 A, 35 V or 40 V, Schottky diode
1 A, 100 V, 1N4002
Suggested Manufacturer
Nichicon, part number UHC1E330MET
Nichicon, part number UHC1V101MPT
TDK, part number TSL0808-330K1R4
TDK, part number TSL0808-330K1R4
Various, part number 1N5819; Sanken, part number AW04
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A8285 and
A8287
LNB Supply and Control Voltage Regulator
ELECTRICAL CHARACTERISTICS
at T
A
= +25°C, V
IN
= 10 to 16 V (unless otherwise noted)
Characteristics
Set-point Accuracy, load and line
regulation
Supply Current
Boost Switch-On Resistance
Switching Frequency
Switch Current Limit
Linear Regulator Voltage Drop
Slew Rate Current on TCAP
Output Voltage Slew Period
Output Reverse Current
Ripple and Noise on LNB Output
Protection Circuitry
Overcurrent Limit
Overcurrent Disable Time
V
IN
Undervoltage Threshold
V
IN
Turn-On Threshold
Power-Not-Good Flag Set
Power-Not-Good Flag Reset
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
I
LIM
t
DIS
UV
OFF
UV
ON
PNG
set
High limit
Low limit
–
Guaranteed turn-off
Guaranteed turn-on
–
550
400
1.2
8.65
8.75
77
82
–
–
700
500
–
9.15
9.25
85
90
165
20
850
600
1.7
9.65
9.75
93
98
–
–
mA
mA
ms
V
V
%V
LNB
%V
LNB
°C
°C
Symbol
V
O1
I
CC
I
CCEN
Test Conditions
Relative to target voltage selected, with:
I
LOAD
= 0 to 500 mA
ENB = Low, LNB output disabled
ENB = High, LNB output enabled, I
LOAD
= 0mA
Min.
-4.5
–
–
–
320
2.0
400
–12.5
7.5
–
–
–
Typ.
0
–
–
400
352
3
600
–10
10
500
1
–
Max.
4.5
7
15
500
384
4.0
800
–7.5
12.5
–
5
50
Units
%
mA
mA
m
kHz
A
mV
μA
μA
μs
mA
mV
pp
R
DSBOOST
T
J
= 25
°C,
I
LOAD
= 500mA
fo
–
V
REG
I
CAP
t
slew
I
OR
V
RN
–
V
IN
= 12 V
V
BOOST
– V
LNB
, no tone signal, I
LOAD
= 500 mA
Charging
Discharging
V
LNB
= 13 to 18 V, TCAP = 6.8 nF, I
LOAD
= 500
mA
ENB = Low, V
LNB
= 28 V with C4 fully charged
See notes 1 and 2
PNG
reset
–
T
J
T
J
See note 1
See note 1
Continued on next page
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A8285 and
A8287
LNB Supply and Control Voltage Regulator
ELECTRICAL CHARACTERISTICS
(continued) at T
A
= +25°C, V
IN
= 10 to 16 V (unless otherwise noted)
Characteristics
Tone Characteristics
Symbol
f
TONE
I
TONE
t
DEL
V
IH
V
IL
I
IL
V
TDI
f
TDI
Z
TDI
V
OL
I
OL
V
IL
V
IH
V
HYS
I
IN
V
OL
I
OL
f
CLK
t
OF
t
BUF
t
HD:STA
t
SU:STA
t
LOW
t
HIGH
t
SU:DAT
t
HD:DAT
t
SU:STO
–
–
Test Conditions
Min.
20
30
–
2
–
–1
260
17.6
–
–
–
Typ.
22
40
–
–
–
–
–
–
8.6
–
–
Max.
24
50
1
–
0.8
1
1000
26.4
–
0.4
10
Units
kHz
mA
μs
V
V
μA
mV
kHz
k
V
A
Tone Frequency
Tone Pull-Down Current
Tone Turn-On and Turn-Off Delays
External Tone Logic Input
Input Leakage
Tone Detector Input Amplitude
Tone Detector Frequency Capture
Tone Detector Input Impedance
Tone Detector Output Voltage
Tone Detector Output Leakage
I
2
C
Interface
Logic Input (SDA,SCL) Low Level
Logic Input (SDA,SCL) High Level
Input Hysteresis
Logic Input Current
Output Voltage (SDA, IRQ)
Output Leakage (SDA, IRQ)
SCL Clock Frequency
Output Fall Time
Bus Free Time Between Stop and Start
Hold Time for Start Condition
Setup Time for Start Condition
SCL Low Time
SCL High Time
Data Setup Time
Data Hold Time
Setup Time for Stop Condition
Using EXTM pin
–
–
–
f
IN
= 22 kHz
600 mV
pp
sinewave
See note 1
Tone present, I
LOAD
= 3 mA
Tone absent, V
O
= 7 V
–
–
–
V
IN
= 0 V to 7 V
I
LOAD
= 3 mA
V
O
= 0 V to 7 V
–
V
IH
to V
IL
See I
2
C Interface Timing Diagram
See I
2
C Interface Timing Diagram
See I
2
C Interface Timing Diagram
See I
2
C Interface Timing Diagram
See I
2
C Interface Timing Diagram
See note1; I
2
C Interface Timing Diagram
See I
2
C Interface Timing Diagram
See I
2
C Interface Timing Diagram
–
2
–
–10
–
–
0
–
1.3
0.6
0.6
1.3
0.6
100
0
0.6
–
–
150
<±1.0
–
–
–
–
–
–
–
–
–
–
–
–
0.8
–
–
10
0.4
10
400
250
–
–
–
–
–
–
900
–
V
V
mV
μA
V
μA
kHz
ns
μs
μs
μs
μs
μs
ns
ns
μs
Continued on next page
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
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