SL1461S [ETC]
WIDEBAND PLL FM DEMODULATOR; 宽带锁相环调频解调器
| 型号： | SL1461S |
| 厂家： | 
ETC |
| 描述： | WIDEBAND PLL FM DEMODULATOR |
| 文件： | 总13页 (文件大小：196K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SEPTEMBER 1993
PRELIMINARY INFORMATION
D.S. 3754 1.6
SL1461
WIDEBAND PLL FM DEMODULATOR
The SL1461 is a wideband PLL FM demodulator, intended
primarily for application in satellite tuners.
The device contains all elements necessary, with the
exception of external oscillator sustaining network and loop
feedback components, to form a complete PLL system
operating at frequencies up to 800MHz.
An AFC with window adjust is provided, whose output
signal can be used to correct for any frequency drift at the head
AFC PUMP
AFC WINDOW ADJUST
VEE
1
2
3
4
5
6
7
8
16
15
14
13
12
AFC OUTPUT
VCC
VIDEO FEEDBACK +
VIDEO –
OSCILLATOR +
OSCILLATOR –
AGC BIAS
end local oscillator
.
VIDEO +
11
10
VIDEO FEEDBACK –
VIDEO OUTPUT
RF INPUT
AGC OUTPUT
RF INPUT
FEATURES
J Single chip PLL system for wideband FM
demodulation
9
J
J
J
J
J
Simple low component count application
Allows for application of threshold extension
Fully balanced low radiation design
High operating input sensitivity
MP16
Fig. 1 Pin connections top view
AGC detect and bias adjust
J 75W video output drive with low distortion
APPLICATIONS
J Satellite receiver systems
Data communications systems
levels
J
Dynamic self biasing analog AFC
Full ESD protection *
J
J
ORDERING INFORMATION
*
Normal ESD handling procedures should be observed
SL1461S/KG/MPAS
6
14
VIDEO
FEEDBACK +
AGC BIAS
8
12
13
VIDEO +
VIDEO –
RF INPUTS
9
7
11
10
1
AGC OUTPUT
VIDEO
FEEDBACK –
VIDEO
OUTPUT
AFC PUMP
4
5
16
LOCAL
OSCILLATOR
AFC OUTPUT
2
AFC WINDOW
ADJUST
Fig. 2 SL1461 block diagram
SL1461
ELECTRICAL CHARACTERISTICS
Tamb=–20°C to )80°C, VCC=)4.5V to )5.5V. These characteristics are guaranteed by either production test or design.
They apply within the specified ambient temperature and supply voltage unless otherwise stated.
Value
Characteristics
Supply current
Units
Conditions
Min
Typ
Max
40
36
mA
MHz
dBm
dBm
MHz/V
%
Operating frequency
Input sensitivity
300
800
–40
Preamp limiting
Input overload
0
VCO sensitivity (dF/dV)
VCO linearity
25
32
39
Refer to application in Fig. 3a
.25
Refer to application in Fig. 3a; with
13.5MHz p–p deviation
Phase detector gain
0.5
0.25
V/rad
V/rad
Differential loop filter
Single ended loop filter
Loop amplifier input
impedance
450
570
25
700
W
Single ended
Single ended
Loop amplifier output
impedance
W
Loop amplifier open loop gain
38
dB
Single ended
Single ended
Loop amplifier gain bandwidth
product
240
MHz
Loop amplifier output swing
1.2
95
Vp–p
Single ended
V
ideo drive output impedance
ideo drive;
55
75
W
V
Luminance nonlinearity
– differential gain
1.9
0.5
1.0
5
2.5
3
%
%
1KW load, See note 3 & 4
75W load, See note 3 & 4
75W load, See note 3 & 4
See notes 1+3 & 4
– differential phase
– intermodulation
Degree
dB
dB
%
–40
– Signal/noise
66
72
0.3
0.4
1KW load, See note 2 & 4
1KW load, See note 3 & 4
1KW load, See note 3 & 4
Maximum load voltage drop 2V
–Tilt
3
– baseline distortion
AGC output current
AGC bias current
2
%
10
0
400
250
400
mA
mA
mA
mA
mA
V
AFC window current
AFC charge pump current
AFC leakage current
AFC output saturation voltage
0
400 A gives 1.5V deadband window
m
50
10
With charge pump disabled
AFC output enabled
0.4
Note 1. Product of input modulation f at 4.43MHz, 13.5MHz p–p deviation and f2 at 6MHz p–p deviation, (PAL chroma and
1
sound subcarriers).
Note 2. Ratio of output video signal with input modulation at 1MHz, 13.5MHz p–p deviation, to output rms noise in 6MHz
bandwidth with no input modulation.
Note 3 Input test signal pre–emphasised video 13.5MHz p–p deviation. Output voltage 600mV pk–pk.
Note 4 See page 3
2
SL1461
TEST CONFIGURATION
BASE BAND VIDEO 1V p–p
VIDEO GENERATOR
ROHDE & SCHWARZ SGPF
TV SAT TEST TX
ROHDE & SCHWARZ SFZ
RF CARRIER FREQ 479.5MHz
FM MODULATION 13.5MHz P–P
PRE–EMPHASISED VIDEO
SL1461 TEST APPLICATION BOARD
See Fig. 3a for details
MONTFORD
TEST OVEN
PRE EMPHASISED BASE BAND VIDEO
VIDEO AMPLIFIER/
DE EMPHASISED NETWORK
DE EMPHASISED BASE BAND VIDEO 1V p–p
VIDEO ANALYSER
ROHDE & SCHWARZ UAF
The video drive characteristics measurements were made using the above test configuration. The maximum figures recorded in
the Electrical Characteristics Table coincide with high temperatures and extremes of supply voltage. No adjustment to the recorded
figures has been made to compensate for the effects of temperature on the external components of the application test board, in
particular the varactor diodes. If operation of the device at high ambient temperatures is envisaged then attention to temperature
compensation of the external circuitry will result in performance figures closer to the stated typical figures.
Note 4.
ABSOLUTE MAXIMUM RATINGS
All voltages are referred to V at 0V
.
EE
Characteristic
Supply voltage
Min
Max
7
Units
Conditions
–0.3
V
V p–p
V
RF input voltage
2.5
RF input DC offset
Oscillator +&–DC offset
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
–55
VCC+0.3
VCC+0.3
VCC+0.3
VCC+0.3
VCC+0.3
VCC+0.3
VCC+0.3
VCC+0.3
VCC+0.3
VCC+0.3
125
V
V
V
V
ideo +&–DC offset
V
ideo feedback +&–DC offset
ideo output DC offset
V
V
AFC pump DC offset
AFC disable DC offset
AFC deadband DC offset
AGC bias DC offset
V
V
V
V
AGC output DC offset
Storage temperature
Junction temperature
V
°C
°C
°C/W
150
MP16 package thermal resistance,
chip to ambient
111
3
SL1461
ABSOLUTE MAXIMUM RATINGS cont.
All voltages are referred to V at 0V
.
EE
MP16 package thermal resistance
chip to case
41
°C/W
Power consumption at 5.5V
ESD protection – pins 1 to 15
ESD protection – pin 16
250
mW
kV
2
Mil–std –883 method 3015 class1
Mil–std –883 method 3015 class1
1.7
kV
V CC
100nF
AGC BIAS
2K
AFC WINDOW ADJUST
50K
27K
47mF
47nF
4K7
100nF
1
2
3
4
5
6
7
8
16
15
120pF
BB833
BB833
14
13
12
22pF
22pF
1K2
1K2
11
10
5K1
120pF
VIDEO OUTPUT
4n7
9
47mF
4K7
1nF
1nF
RF INPUT
Fig.3. Standard application circuit with oscillator referenced to ground
V CC
100nF
AGC BIAS
AFC WINDOW ADJUST
2K
50K
27K
47mF
47nF
4K7
100nF
1
2
3
4
5
6
7
8
16
15
14
13
12
220R
82pF
BB833
BB833
1K2
1K2
620R
82pF
11
10
5K1
VIDEO OUTPUT
4n7
9
47mF
1nF
4K7
1nF
RF INPUT
Fig.3a Application circuit used for video drive characterisation measurements
4
SL1461
FUNCTIONAL DESCRIPTION
The SL1461 is a wideband PLL FM demodulator, optimised
for application in satellite receiver systems and requiring a
minimum external component count. It contains all the
elements required for construction of a phase locked loop
circuit, with the exception of tuning components for the local
oscillator, and an AFC detector circuit for generation of error
signal to correct for any frequency drift in the outdoor unit local
oscillator. A block diagram is contained in Fig. 2 and the typical
application in Fig. 3.
are shown in Fig. 9.
The output of the preamplifier is fed to the mixer section
which is of balanced design for low radiation. In this stage the
RF signal is mixed with the local oscillator frequency, which is
generated by an on–board oscillator. The oscillator block uses
an external varactor tuned sustaining network and is
optimised for high linearity over the normal deviation range. A
typical frequency versus voltage characteristic for the
oscillator is contained in Fig. 7. The loop output is designed to
compensate for first order temperature variation effects; the
typical stability is shown in Fig. 8
The internal pin connections are contained in Fig.6/6a.
The output of the mixer is then fed to the loop amplifier
around which feedback is applied to determine loop transfer
characteristic . Feedback can be applied either in differential
or single ended mode; if the appropriate phase detector gains
are assumed in calculating loop filters, both modes should
give the same loop response.
In normal applications the second satellite IF frequency of
typically 402 or 479.5MHz is fed to the RF preamplifier, which
has a working sensitivity of typically –40 dBm, depending on
application and layout. The preamplifier contains an RF level
detect circuit, which generates an AGC signal that can be used
for controlling the gain of the IF amplifier stages, so
maintaining a fixed level to the RF input of the SL1461, for
optimum threshold performance. The bias point of the AGC
circuit can be adjusted to cater for variation in AGC line voltage
requirement and device input power. The typical AGC curves
The loop amplifier drives a 75W output impedance buffer
amplifier, which can either be connected to a 75
W
load or used
to drive a high input impedance stage giving greater linearity
and approximately 6dB higher demodulated signal output
level.
DESIGN OF PLL LOOP PARAMETERS
C1
R2
GAIN = K VOLT/RAD
D
RF INPUT
R1
BASEBAND OUTPUT
GAIN = K RAD SEC/VOL
T
0
VCO
Fig.
4
The SL1461 is normally used as a type 1 second order loop
and can be represented by the above diagram. For such a
system the following parameters apply;
where:
K0 is the VCO gain in radian seconds per volt
KD is the phase detector gain in volts per radian
wn is the natural loop bandwidth
z
is the loop damping factor
R1 is loop amplifier input impedance
t1 + C1.R1
t2 + C1.R2
and
Note:
K
K
is dependant on sensitivity of VCO used.
= 0.25V/rad single ended, 0.5V/rad differential
O
D
From these factors the loop 3dB bandwidth can be determined
from the following expression;
K0KD
t1 +
w2n
2
2
2
2z
wn
w3dB + w2n(2z2 ) 1) " wn2 (2z ) 1) ) 1
Ǹ
t2 +
1
Ǹ
2
Which approximates to w3dB + 2wnĂĂwhenĂĂz +
5
SL1461
AFC FACILITY
The SL1461 contains an analog frequency error detect
circuit, which generates DC voltage proportional to the
integral of frequency error. If the incident RF is high then the
AFC voltage increases, if low then the voltage decreases. The
AFC voltage can then be converted by an ADC to be read by
the micro controller for frequency fine tuning; if used in an I2C
system it is recommended the device is used with either the
SP5055 or SP5056 frequency synthesiser which contains an
internal ADC readable via the I2C bus.
compared with two reference voltages, corresponding to the
extremes of the deadband, or window. These voltages are
variable and set by the window adjust input.
The comparators produce two digital outputs
corresponding to voltages above or below the voltage window
,
or frequency above or below deadband. These digital control
signals are used to control a complimentary current source
pump. The current signals are then fed to the input of an
amplifier which is arranged as an integrator, so integrating the
pulses into a DC voltage.
If the frequency is correctly aligned both the current source
and sink are disabled, therefore the DC output voltage
remains constant. There will be a small drift due to component
leakage; the maximum drift can be calculated from;
The voltage corresponding to frequency alignment is
arbitrary and user defined; if used with the SP5055 it is
suggested the aligned voltage is 0.375 V , corresponding to
CC
the centre code of the ADC on port 6.
The AFC detect circuit contains a deadband centred
around the aligned frequency. The deadband can be adjusted
from zero window to approximately 25MHz width assuming an
oscillator dF/dV of 15MHz/V. If the incident RF is within this
window the AFC voltage does not integrate, except by
component leakage.
VCC
dV
dt
I
2500.C
+
whereĂĂĂI +
Ă,ĂĂ C + CEXT
REXT
With reference to Fig.5; in normal operation the
demodulated video is fed to a dual comparator where it is
WINDOW
ADJUST
VHI
VALIGN
VLO
FREQ
VCC
VCC
+
–
REXT
CEXT
BASEBAND
VIDEO
VAFC
+
–
VEE
Fig. 5 AFC system block diagram
6
SL1461
VCC
AGC BIAS
VREF; 2.7V
VREF; 2V
AGC OUTPUT
AGC output
AGC bias adjust
VREF; 3V
AFC WINDOW
2x1500
RF INPUTS
VREF; 1.6V
RF inputs
AFC window adjust
VCC
AFC PUMP
VIDEO +
10K
VIDEO –
AFC OUTPUT
330
330
2mA
2mA
AFC output stage
Video amp outputs
Fig.6 SL1461 I/O port internal circuitry
7
SL1461
VREF; 2.5V
2 x 5k
OSCILLATOR +
OSCILLATOR –
Local oscillator
FROM PHASE DETECTOR
2x570
VCC
68
VIDEO
OUTPUT
105
VIDEO
FEEDBACK +
VIDEO
FEEDBACK –
4mA
Video amp feedback inputs
Video output drive
Fig. 6a SL1461 I/O port internal circuitry
FREQ MHz
482
FREQ MHz
520
500
480
460
440
420
400
360
481
480
479
1
1.5
2
2.5
DC VOLTAGE
Fig. 7 Typical VCO frequency vs DC control voltage
3
3.5
4
4.5
5
478
–20
80
20
TEMP/°C
Fig. 8 SL1461 VCO centre frequency uncompensated
temperature stability
.
8
SL1461
2.0
1.5
1.0
0.5
AGC
OUTPUT
VOLTAGE
AGC BIAS RESISTOR 5.1K
AGC BIAS CURRENT 297mA
AGC LOAD RESISTOR 3.9K
AGC BIAS RESISTOR 10.5K
AGC BIAS CURRENT 150mA
AGC LOAD RESISTOR 4.7K
AGC BIAS RESISTOR 32K
AGC BIAS CURRENT 52mA
AGC LOAD RESISTOR 10K
–70
–60
–50
–40
–30
–20
–10
0
VCC = 5.0 VOLTS
RF INPUT LEVEL (dBm) UNMODULATED
Fig.9 SL1461 AGC output voltage for differing values of AGC bias resistor
APPLICATION NOTES
Capture range
Under conditions when there is no RF input signal present,
the SL1461 may react to spurious radiation from the free
running oscillator coupling into the RF inputs. Because of the
constant phase error between the VCO input to the phase
detector and the spuriously coupled signal via the RF input,
the phase comparator will drive the control voltage to either the
bottom or the top of the range.
In such a case, the capture range will be asymmetrical
about the VCO free running frequency, since any control
voltage will only be able to tune the VCO in one direction if the
tuning voltage is already at the max or min.
S–curve. When the oscillator is sitting in the centre of the
S–curve, the two video outputs will be at the same DC voltage.
RF oscillator design
The standard application circuit for the SL1461 is shown in
Fig.3 The layout of the VCO tank should follow normal good
RF techniques – ie as compact as possible. This will minimise
parasitics, thus giving improved VCO linearity and stability.
The PCB layout used for testing purpose is shown in Fig. 11.
This effect can be avoided by driving the RF input
differentially or achieving good common mode rejection to the
VCO signal.
The lock range is independant of the above effects and will
be symmetric about the centre of the phase detector S–curve
provided the VCO is correctly aligned.
Setting up of oscillator
The VCO should be set up so that the desired input RF
frequency is at the centre of the lock range. This will coincide
with the centre of the S–curve and the point at which the AFC
toggles when set to zero deadband.
The easiest way to centralise the VCO is to input an RF
carrier which is being modulated by a low frequency
squarewave. The tuning coil(s) should be adjusted until the
EXAMPLE
AFC voltage toggles between 0.2V and V
the FM deviation of the squarewave used, the more accurate
the setting will be.
A pre–emphasised video input containing black to white
transitions can also be used for this setting, since the DC
content in a pre–emphased video is much less than that in non
pre–emphasised video. This is important as any dc content in
the input waveform will introduce an offset in the AFC transition
point.
. The smaller
CC–0.7V
Loop out of lock
Tuning voltage =4.3V (maximum)
frequency =520MHz (maximum
It is only possible to capture signals below this frequency since
the VCO is already at its maximum frequency
Testing of capture range should be done with the device
operating under normal conditions. An input signal of between
–35dBm to –10dBm is suitable for such a measurement.
.
The setting can be confirmed by measuring the DC voltage
on the two video outputs, the voltages should be the same
when the oscillator is centred around the incoming frequency
.
This DC measurement must be carried out with an
unmodulated carrier of the required frequency. Modulation
must not be present, since by definition, the dc voltages would
be changing, thus making accurate measurement difficult.
Lock range
Lock range should be symmetric about the centre of the
9
SL1461
NOTES
Circuit schematic is
shown in Fig. 3.
TP1=VIDEO –
TP2=VIDEO +
TP3=AGC O/P
TP4=AFC O/P
All surface mount
components mounted
on underside of board
Fig. 11 Layout of demo board with oscillator referenced to GND
10
SL1461
11
SL1461
PACKAGE DETAILS
Dimensions are shown thus: mm (in). For further package information please contact your local Customer Service Centre.
9.80/10.01
(0.386/0.394)
16 LEAD MINIATURE PLASTIC MP16
0.69 (0.027) MAX
AT 4 PLACES
PIN 1
1.27 (0.050) NOM
PIN SPACING
PIN 1 IDENTIFICATION
0.25/0.51
(0.010/0.020) X45°
0.19/0.25
(0.007/0.010)
8°MAX
0.41/1.27
(0.016/0.050)
0.35/0.49
(0.014/0.019)
0.10/0.25
(0.004/0.010)
5.80/6.20
(0.228/0.244)
HEADQUARTERS OPERATIONS
CUSTOMER SERVICE CENTRES
GEC PLESSEY SEMICONDUCTORS
Cheney Manor, Swindon,
F
FRANCE & BENELUX Les Ulis Cedex Tel: (1) 64 46 23 45 Tx: 602858F
Fax: (1) 64 46 06 07
Wiltshire SN2 2QW, United Kingdom.
F
F
F
F
GERMANY Munich Tel: (089) 3609 06 0 Tx: 523980 Fax: (089) 3609 06 55
T
el: (0793) 518000
ITALY Milan Tel: (02) 66040867 Fax: (02) 66040993
Fax: (0793) 51841
1
JAPAN Tokyo Tel: (03) 3296–0281 Fax: (03) 3296–0228
NORTH AMERICA Integrated Circuits and Microwave Products,
Scotts Valley, USA Tel: (408) 438 2900 Fax: (408) 438 7023
Hybrid Products, Farmingdale, USA Tel: (516) 293 8686
Fax: (516) 293 0061
GEC PLESSEY SEMICONDUCTORS
.O. box 660017 1500 Green Hills Road,
P
F
F
F
SOUTH EAST ASIA Singapore Tel: (65) 3827708 Fax: (65) 3828872
SWEDEN Stockholm Tel: 46 8 7029770 Fax: 46 8 6404736
UNITED KINGDOM & SCANDINAVIA
Scotts Valley, California 95067–0017,
United States of America. Tel: (408) 438 2900
Fax: (408) 438 5576
Swindon Tel: (0793) 518510 Tx: 444410 Fax: (0793) 518582
These are supported by Agents and Distributors in major countries world–wide.
E
GEC Plessey Semiconductors 1993 Publication No. D.S. 3754 Issue No. 1.6 September 1993
This publication is issued to provide outline information only, which (unless agreed by the Company in writing) may not be used, applied or reproduced for any purpose nor form part of
any order or contract nor to be regarded as a representation relating to the products or services concerned. No warranty or guarantee express or implied is made regarding the
capability, performance or suitability of any product or service. The Company reserves the right to alter without notice the specification, design, price of any product or service.
Information concerning possible methods of use is provided as a guide only and does not constitute any guarantee that such methods of use will be satisfactory in a specific piece of
equipment. It is the user’s responsibility to fully determine the performance and suitability of any equipment using such information and to ensure that any publication of data used is up
to date and has not been superseded. These products are not suitable for use in any medical products whose failure to perform may result in significant injury or death to the user. All
products and materials are sold and services provided subject to the Company’s conditions of sale, which are available on request.
12
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suitability of any product or service. Information concerning possible methods of use is provided as a guide only and does not constitute any guarantee that such methods of
use will be satisfactory in a specific piece of equipment. It is the user’s responsibility to fully determine the performance and suitability of any equipment using such
information and to ensure that any publication or data used is up to date and has not been superseded. Manufacturing does not necessarily include testing of all functions or
parameters. These products are not suitable for use in any medical products whose failure to perform may result in significant injury or death to the user. All products and
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2
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