A8282SLBTR [ETC]
LNB Supply and Control Voltage Regulator ; LNB电源与控制稳压器\n
| 型号： | A8282SLBTR |
| 厂家： | 
ETC |
| 描述： | LNB Supply and Control Voltage Regulator
|
| 文件： | 总10页 (文件大小：297K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
8281/8282
LNB SUPPLY AND CONTROL
VOLTAGE REGULATOR
11/18/2002
Intended for analog and digital satellite receivers, the 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 the LNB downconverter via the coaxial cable.
ABSOLUTE MAXIMUM RATINGS
at T = +25°C
A
If the device is in stand-by mode (EN terminal LOW), the regulator
output is disabled. This is to allow the antenna downconverters to be
supplied/controlled by other satellite receivers sharing the same coaxial
cable. In this mode the device will limit reverse current.
Load Supply Voltage, VIN ...........................47 V
Output Current, IOUT............ Internally Limited*
Output Voltage, VOUT........................ -1V to 22 V
Switching Node, LX .......................................-1V
Logic Input ..................................... -0.3 V to 7 V
The A8281 is supplied in a 16-lead plastic SOIC with copper batwing
tab (suffix “LB”). The A8282 is supplied is a 24-lead plastic SOIC with
copper batwing tab (suffix “LB”). Operating temperature range is standard
classification (suffix "S").
Package Power Dissipation (T = +25°C), PD
A
A8281SLB.......................... 56 °C/W**
A8282SLB.......................... 50 °C/W**
The A8282 is available for improved power dissipation as well as
allowing direct replacement of Allegro’s first generation LNBR device, the
A8283SLB, with the exception of the bypass switch.
Operating Temperature Range,
TA ................................ -20°C to +85°C
Junction Temperature, TJ ......................... +150°C
Storage Temperature Range,
FEATURES
TS............................... -55°C to +150°C
LNB selection and stand-by function
Built-in tone oscillator factory trimmed to 22 kHz facilitates DiSEqC™
encoding
* 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 temperature of 150°C.
** Measured on a PCB with 2 oz copper with ground area
of 1 square inch.
Tracking switch-mode power converter for lowest dissipation
Externally adjustable short-circuit protection
LNB short-circuit protection and diagnostics
Auxiliary modulation input
Internal over temperature protection
Reverse current protection
Cable Length Compensation (A8282 only)
This device incorporates features that have patents pending.
Always order by complete part number:
Part Number
A8282SLBTR
A8282SLB
Package
24 Lead SOIC Tape/Reel
24 Lead SOIC
A8281SLB
16 Lead SOIC
8281/8282
100uH
200 mohm
VBULK
+VIN
100uF
.1uF
100uF
.1uF
VIN
LX
SENSE
VPUMP
-
Over-
Current
EN
5V Regulator
352Khz
+
Charge Pump
135mV
(8282 Only)
VINT
-
Buck Converter
Divide
+
4.7uF
by 2
900mV
15
-
180uH
LNB
+
Divide
by 16
22 Khz Tone
Generation
ENT
OLF
.22uF
Diseq
100nF
Termination
EXTM
Output Voltage
Select
TSD
OverCurrent
Fault
.1uF
GND
TCAP
10nF
Output Voltage Select Table – A8282SLB
Output Voltage Select Table – A8281SLB
VSEL0
VSEL1
LLC
L
VLNB
13
VSEL1
VLNB
13
L
L
L
L
L
H
L
14
H
18
L
H
H
L
18
L
H
L
19
H
H
H
H
12
L
H
L
13
H
H
20
H
21
8281/8282
ELECTRICAL CHARACTERISTICS at TJ = +125°C, CLNB = 100nF VIN=VINMIN to 47V (unless noted otherwise)
Limits
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Units
VIN Supply Voltage Range
Output Voltage
VINMAX
VINMIN
VLNB
47
4.5
4.5
0.8
V
4.5+Vo
-4.5
Relative to Voltage Select Table
ILOAD = 6mA to 750mA
0
0
%
%
Output Voltage
VLNB
ENT=H, ILOAD=12mA to 750mA
Average Voltage of LNB
-4.5
2.0
Logic Input Voltage
Vil
Vih
V
V
Logic Input Current
Supply current
Iih
Vih=5 V
< 1.0
.25
6
10
1
µA
mA
mA
Ω
ICC
EN = L
ICCEN
RDSBUCK
EN = H, ILOAD = 0 mA
TJ = 25 °C, IOUT=750mA
TJ =125 °C, IOUT=750mA
10
Buck Switch On Resistance
.57
.8
.67
.94
2.5
384
1100
Ω
Buck Switch Current Limit
Switching frequency
IBLIM
fo
1
A
fTONE * 16
320
700
352
900
.375
kHz
mV
Ω
Linear regulator voltage drop
Linear Regulator On Resistance
∆VBUCK
RDSLNB
VSENSE –Vo, ENT = L, ILOAD=750mA
ILOAD = 750mA, VIN = 18V, TJ = 25 °C
Output Select = 18V
Tone Characteristics
Tone Frequency
fTONE
ATONE
DCTONE
tr, tf
ENT=H
20
0.4
40
5
22
24
0.9
60
15
6
kHz
VPP
%
Tone Amplitude
ENT = H, ILOAD = 12mA to 750mA
ILOAD = 12mA to 750mA
ENT=H, ILOAD = 12mA to 750mA
.65
Tone Duty Cycle
Tone rise or fall time
External Modulation Gain
10
µs
gEXTM
∆VOUT/∆VEXTM, f = 22 kHz square wave, ILOAD
=
4
5.0
V/V
12mA to 750mA
EXTM Input Range
∆VEXTM
Ac coupled
100
4
125
10
mVpp
External Modulation Impedance
ZEXTM
f = 22kHz
kΩ
NOTES: 1. Typical Data is for design information only.
2. Negative current is defined as coming out of (sourcing) the specified device pin.
8281/8282
ELECTRICAL CHARACTERISTICS at TJ = +125°C, CLNB = 100nF VIN=VINMIN to 47V (unless noted otherwise)
Limits
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Protection Circuitry
Output Leakage Current
Overload flag terminal logic low
Output reverse current
Ioz
Vol
Voh=5.5 V
< 1.0
0.28
1.0
10
.5
µa
V
Iol=8 mA
IOR
EN=L, VLNB= 22 V VIN =22 V or VIN floating
5
mA
mV
°C
°C
Current Limiting Threshold
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
VOMTH
TJ
115
135
165
20
155
∆TJ
NOTES: 1. Typical Data is for design information only.
2. Negative current is defined as coming out of (sourcing) the specified device pin.
8281/8282
Functional Description
Buck Regulator. A current-mode buck converter
provides the linear regulator a supply voltage that tracks the
requested LNB output voltage. The buck converter operates
at 16 times the internal tone frequency, nominally 352kHz.
Internal Tone Modulation. The ENT (Tone Enable)
terminal activates the internal tone signal modulating the dc
output with a 650mV peak to peak, trapezoidal waveform.
The internal oscillator is factory trimmed to provide a tone
of 22 kHz +/- 2 kHz. No further adjustment is required.
Burst coding of the 22 kHz tone can be accomplished, due to
the fast response of the ENT input and rapid tone response.
This allows implementation of the DiSEqC™ protocols.
The tracking regulator provides minimum power dissipation
across the range of output voltages by adjusting the SENSE
pin voltage 900 mV nominally above the LNB output
selected. The tracking Regulator also provides adequate
headroom for tone injection.
External Tone Modulation. To improve design
flexibility and to allow implementation of proposed LNB
remote control standards, an analog modulation input
terminal is available (EXTM). An appropriate dc blocking
capacitor must be used to couple the modulating signal
source to the EXTM terminal. If external modulation is not
used, the EXTM terminal should be bypassed to ground via
a .1uF ceramic capacitor. The input amplitude should stay
within 100 to 125mVpp to guarantee the DiSEqC™
amplitude specification over the output current range.
Linear Regulator. The output linear regulator will sink
and source current. This allows tone modulation into a
capacitive load of 100nF for the output current range of
12mA to 750mA.
Slew Rate Control. The programmed output voltage
rise and fall times can be set by an internal 25 kΩ resistor
and an external capacitor located on the TCAP terminal. The
range of acceptable capacitor values is 4.7nF to 47nF. This
feature only affects the turn on and programmed voltage rise
and fall times. Modulation is unaffected by the choice of
TCAP. If LNB output voltage rise and fall time is not a
concern, the TCAP terminal should use a 100nF ceramic as
a default value to minimize output noise. If a small value
capacitor value is used, the rise time will be limited by the
time required to charge the VBULK capacitor.
Short Circuit Limit Regulator. The LNB output is
current limited. The short-circuit protection threshold is set
by the value of an external resistor, RSENSE in conjunction
with an internal 135mV+/- 20mV reference voltage, VOMTH
.
IOM = VOMTH/RSENSE
The sense resistor should be chosen based on maximum DC
plus AC (tone), load current required, internal VOMTH
tolerance, and sense resistor accuracy. For 750mA
applications, a precision 140mohm resistor is recommended.
For 500mA applications the resistor value can be raised to
200mohms.
In operation, the short-circuit protection produces current
limiting at the input due to the tracking converter. If the
output is shorted, the linear regulator will limit the output
current to IOM
.
Fault Output. Short-circuit or thermal shutdown will
cause the OLF terminal, an open-drain diagnostic output
flag, to go LOW.
8281/8282
Typical Application Diagram
C1
N/C
OLF
EXTM
CINT
VINT
C2
R1
C3
VBULK
N/C
PUMPX
VPUMP
CPUMP
GND
TCAP
Vin
CBULK
L1
Rs
N/C
GND
GND
SENSE
LNB
GND
ENT
CBYP
ENB
Control
Inputs
LX
VSEL0
VSEL1
LLC
VIN
D1
CIN
TCAP
CTCAP
D2
.22uF
CLNB
15 Ohm
180uH
+30V
F-Connecter
Optional
Diseq
Termination
Description
.1uF/50V ceramic X7R/X5R
Representative Component
C1-3, CBYP, CLNB
CIN
100uF Low ESR electrolytic 50V
100uF Low ESR electrolytic/35V
4.7uF/16V tantulum/electrolytic
1.5A Schottky/40V or 50V
1A Silicon Diode/25V
Nichicon UHD1H101MPT
Nichicon UHC1V101
CBULK
CINT
D1
D2
L1
Sanken EK04
Sanken EU01
TDK TSL1112-101K1R4
Falco D08018, Coilcraft DR0808,
TDK TSL0808-101KR80
TDK TSL1112S-181K1R0-PF
Meritek CR04R140F
100uH (750mA max Iload)
100uH (500mA max Iload)
180uH (750mA Iload)
140-200mOhm sense resistor .25W
10nF ceramic X7R/X5R
1M 5%
L2
RS
CTCAP
R1
8281/8282
6. A two-sided board with ground planes on both sides of
Component Selection.
the PCB will help optimize the power dissipation.
Typically several copper Vias under the device are used
to connect the ground planes and enhance thermal
performance.
Input Capacitor (CIN). An electrolytic should be located as
close to the device as possible. The input current is a square
wave with fast rise and fall times so the capacitor must be
able to handle the rms current without excessive temperature
rise. The value of the capacitor is not as important as the
ESR. The power dissipated in the input electrolytic is
Noise Immunity. LNB systems can have a 50mV peak
specification for noise on the coaxial cable. This is easily
achievable with the A8282 with proper layout and following
a few guidelines.
Pd(CIN) = IRMS^2*ESR
The worse case Irms is with maximum ILOAD, minimum
VIN, and maximum VOUT (highest switch duty cycle).
Choose a capacitor with a ripple current rating greater than
1. Use a low ESR capacitor for VBULK, 400mohm
maximum is recommended.
2. The LNB output is sensitive to the TCAP reference pin.
Keep the PCB traces short and location of the bypass
capacitor close to the device. This pin is a high
impedance node and noise can be induced from the
proximity to an unshielded inductor. If the inductor can
not be placed far enough away to avoid this noise pickup,
it is important to ensure that the induced voltage is out of
phase with the switching node LX. Rotating the inductor
can change the phase of the induced voltage.
ILOAD* 1.2*VOUT(MAX)/VIN(MIN)
Buck Inductor (L1). A 100uH power inductor is appropriate
for all operating conditions. The rated saturation current of
the inductor must be > 1.3A. The dc resistance should be
less than 350mohms, the smaller the better to maximize
efficiency.
3. Be sure to place a 1uF to 10uF capacitor on internal
reference VINT.
Clamp Diode (D1). A schottky diode is required for the
switching node LX. The diode should be rated at 1.5 times
the maximum load current.
4. Bypass the EXTM pin with a .1uF ceramic to GND.
5. Increasing output capacitance will attenuate noise,
however this must be traded off with the requirement for
low cable capacitance for 22khz-tone transmission.
Output Capacitor (CBULK). A low ESR electrolytic is
recommended to minimize the Vpp ripple voltage. Less than
40mV Vpp is a reasonable goal.
Vpp =ESR*IRIPPLE
IRIPPLE= (VBULK*(1-VBULK/VIN))/(L1*352khz)
Layout Notes.
1. Use a star ground approach. Connect the common
ground to the ground plane at the device ground pins.
The SOIC-24 has 2 pins on each side connected to the
package power ground tab. This allows the analog and
power ground to be kept separate on the PCB up to the
device.
2. Keep the sense resistor PCB trace as short and wide as
possible to lower trace resistance.
3. Connect the bypass capacitors as close to the device as
possible. The lower valued ceramic capacitors should be
closer to the device than electrolytics.
4. If using an unshielded power inductor for the buck
switch, place as far away from the device as possible.
The resulting EMI can result in additional noise on the
LNB output.
5. Place the TCAP capacitor as close to the device as
possible.
8281/8282
13V to 18V Transition. The LNB output can be rapidly
Power Dissipation. The power dissipated and
operating junction temperature of the 8281 and 8282 can be
estimated to ensure the device operates within desired
thermal budget.
switched between a high and low setting as a method of
receiver to LNB communication. The TCAP capacitor will
control the slew rate based on the RC charging.
The total chip power is contributed by three components.
tRISE/FALL = 25K*CTCAP*ln(V1/V2)
Pd_bias = VIN * (ICCEN- 4mA)
Small values of TCAP are used when the transition time is
desired to be less than a millisecond. In this case, the
minimum rise time is limited by the charge time of the
switching regulators output capacitor. This is dependent on
the LNB load current, peak current limit in the buck switch,
and the output amplitude change.
Pd_buck = ILOAD^2 * RDSBUCK * VBULK /VIN
Pd_lin = ∆VBUCK * ILOAD
PTOT = Pd_bias + Pd_buck + Pd_lin
tRISE = C_bulk * (v2-v1)/(I_ave)
Where VBULK = ∆VBUCK + ILOAD* RSENSE + VLNB
ICCEN, ∆VBUCK, and RDSBUCK can be taken from the
specification table. RDSBUCK is a function of
junction termperature. The RDSON will rise
approximately 2.7mohm/°C.
Where I_ave is the average current available to charge the
output capacitor and can be estimated by:
I_ave = 1.4A - I_load
The junction temperature can be estimated by:
Note that this is only a limitation due to the ability to charge
the output capacitor on a low to high change of the LNB
voltage. For high to low transitions, the output voltage will
be slew limited by TCAP.
TJ = PTOT * RØJA + TA
OR
TJ = PTOT * RØJT + TTAB
Where RØJT
=
=
=
5.6°C /W
The minimum value for TCAP should be 4.7nF.
TA
Ambient Temperature °C
50°C /W for A8282SLB
56°C /W for A8281SLB
RØJA
RØJA numbers for a typical two sided, 2 oz. copper, PC
board layout with copper ground plane of 1 square inch.
Additional copper ground plane area, multi- level boards, etc
can reduce the effective RØJA
.
DiSEqCTM. The 22khz tone is specified to be compatible
to coaxial cable bus standards available from
www.eutelsat.com. The A8282 LNB output will be able to
drive the DiSEqC termination network. This terminator
typically consists of a 180uH inductor, used to pass the dc
current with minimal loss, and a 15 ohm parallel resistor to
provide the recommended source impedance at 22khz.
Unidirectional communication systems such as DiSEqC 1.0
do not need this termination and the LNB output can be
directly connected to the coaxial cable.
8281/8282
Output Voltage Adjust. It is possible to fine tune the LNB
output voltage to comply with the DirectTV specification by
connecting a 1M resistor from pin VINT to TCAP.
The LNB is output gained up by 6 from the TCAP voltage
as shown. The 1M resistor pulls the LNB voltage up 440mV
from the 13V nominal setting of the voltage select DAC by
sourcing approximately 2.76µA into the TCAP node.
Internal 5V
VINT
Reference
1M
TCAP
_
LNB
X 6
LNB Voltage
Select
+
25K
Capacitive Loading. The linear regulator sink current
is limited which can cause overshoot of the 22Khz tone.
This effect only appears with low levels of output current
combined with high values of output capacitance. This
relationship is chart below. Points above the line will not
have excessive overshoot.
IOUT(ma) vs Cload (uf)
120
100
1.5
80
1
60
0.47
40
20
0
0.3
0.22
0.1
0.1
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
8281/8282
Pin Name
Pin Description
8281SLB
8282SLB
SO-24
24
SO-16
EXTM
OLF
External modulation input
1
2
Overload flag output
2
VBULK
GND
Tracking supply voltage to linear regulators
Ground tab
3
3
4
6,7
8
SENSE
LNB
Current limit setup resistor
5
Output voltage to LNB
6
9
LX
Inductor drive point
7
10
VIN
Supply input voltage
8
11
TCAP
LLC
Capacitor for setting the rise and fall time of the outputs
Logic input: increases output voltage by 1 V for line length
Logic input: output voltage select
Logic input: output voltage select
Logic input: enables switcher and outputs
Logic input: enable internal modulation
Ground tabs
9
12
-
13
VSEL1
VSEL0
EN
10
-
14
15
11
12
13
14
15
16
-
16
ENT
17
GND
18,19
20
CPUMP
VPUMP
PUMPX
VINT
N/C
High side of charge-pump cap
Gate supply voltage for high side drivers
Charge-pump drive
21
22
Internal regulated supply
23
No Connect
1,4,5
相关型号：
A8282SLBTR-T
Switching Regulator, Current-mode, 2.5A, 384kHz Switching Freq-Max, PDSO24, LEAD FREE, SOIC-24
ALLEGRO
A8283CLB
Switching Regulator, Current-mode, 1A, 384kHz Switching Freq-Max, PDSO22, POWER, SOIC-24
SANKEN
A8283SB
Switching Regulator, Current-mode, 1A, 384kHz Switching Freq-Max, PDIP22, POWER, BATWING, PLASTIC, DIP-24
SANKEN
A8283SLBTR
Switching Regulator, Current-mode, 1A, 384kHz Switching Freq-Max, PDSO24, POWER, SOIC-24
ALLEGRO
©2020 ICPDF网 联系我们和版权申明