L2572 [UTC]

WIDEBAND PLL FM DEMODULATOR; 宽带锁相环调频解调器


型号：	L2572
厂家：	Unisonic Technologies
描述：	WIDEBAND PLL FM DEMODULATOR 宽带锁相环调频解调器
文件：	总14页 (文件大小：251K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

UNISONIC TECHNOLOGIES CO., LTD

L2572

LINEAR INTEGRATED CIRCUIT

WIDEBAND PLL FM

DEMODULATOR

DESCRIPTION

As a wideband PLL FM demodulator, the UTC L2572 is

intended for application in satellite tuners primarily.

The device includes all the necessary elements, with

external oscillator sustaining network and the exception of

loop feedback components, to form a PLL system operating

at frequencies up to 800MHz completely.

SOP-16

An AFC with window adjust (whose output signal can be

used to correct for any frequency drift at the head end local

oscillator) is provided.

*Pb-free plating product number: L2572L

FEATURES

* Constant voltage and constant current control

* Single chip PLL system for wideband FM demodulation

* Simple low component count application

* Allows for application of threshold extension

* Fully balanced low radiation design

* High operating input sensivity

* Improved VCO stability with variations in supply or

temperature

* AGC detect and bias adjust

* 75Ω video output drive with low distortion levels

* Dynamic self biasing analog AFC

* Full ESD Protection

ORDERING INFORMATION

Ordering Number

Package

Packing

Normal

Lead Free Plating

L2572-S16-R

L2572-S16-T

L2572L-S16-R

L2572L-S16-T

SOP-16

Tape Reel

Tube

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PIN CONFIGURATION

PIN DESCRIPTION

PIN NO.

PIN NAME

AFC PUMP

I/O

DESCRIPTION

Current pump, integrating the signal pulses into a DC voltage

Set the AFC deadband voltages corresponding the frequency

GND

AFC WINDOW ADJUST

V_EE

OSCILLATOR+

OSCILLATOR-

AGC BIAS

Oscillator positive signal

Oscillator negative signal

Set the AGC bias

AGC OUTPUT

RF INPUT

Output AGC DC voltage

Input signal

RF INPUT

Input signal

VIDEO OUTPUT

VIDEO FEEDBACK-

VIDEO+

Output video signal

Feedback the video negative signal

Video positive signal

VIDEO-

Video negative signal

VIDEO FEEDBACK+

V_CC

Feedback the video positive signal

Input V_CC

AFC OUTPUT

Output AFC DC voltage

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LINEAR INTEGRATED CIRCUIT

BLOCK DIAGRAM

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TEST CONFIGURATION

BASE BAND VIDEO 1V p–p

VIDEO GENERATOR

TV SAT TEST TX

ROHDE &

SCHWARZ SGPF

SCHWARZ SFZ

RF CARRIER FREQ 479.5MHz

FM MODULATION 13.5MHz P–P

PRE–EMPHASISED VIDEO

TEST APPLICATION BOARD

See Fig. 1 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

Using the above test configuration the video drive characteristics measurements were made. In the Electrical

Characteristics Table the maximum figures recorded coincide with extremes of supply voltage and high temperatures.

There’s 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 the varactor diodes particularly. Attention to temperature

compensation of the external circuitry will result in performance figures closer to the stated typical figures if operation

of the device at high ambient temperatures is envisaged.

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ABSOLUTE MAXIMUM RATINGS (V_EE=0V)

PARAMETER

SYMBOL

V_CC

RATINGS

-0.3~7

UNIT

Supply Voltage

RF Input Voltage

RF Input DC Offset

Oscillator ± DC Offset

Video ± DC Offset

V_IN(RF)

2.5

V_P-P

V_{IN_RF(OFF)}

V_OSC(OFF)

-0.3~V_CC+0.3

250

V_VDO(OFF)

Video Feedback ± DC Offset

Video Output DC Offset

AFC Pump DC Offset

V_AFC(OFF)

AFC Disable DC Offset

AFC Deadband DC Offset

AGC Bias DC Offset

V_AGC(OFF)

P_D

AGC Output DC Offset

Power Dissipation (at 5.5V)

ESD Protection - Pin 1 to 15

ESD Protection - Pin 16

Junction Temperature

Storage Temperature

°C

ESD

1.7

T_J

150

T_STG

-55~125

Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged.

Absolute maximum ratings are stress ratings only and functional device operation is not implied.

THERMAL DATA

Parameter

SYMBOL

Θ_JA

RATINGS

111

Unit

°C/W

Junction to Ambient

Junction to Case

Θ_JC

ELECTRICAL CHARACTERISTICS

(Ta = -20°C~+80°C, V_CC= +4.5V ~ +5.5V. Either design or production test guarantee the electrical characteristics.

Unless otherwise stated they apply within the specified ambient temperature and supply voltage.)

PARAMETER

Supply Current

SYMBOL

V_CC

CONDITIONS

MIN TYP MAX UNIT

Operating Frequency

Input Sensitivity

F_OPR

300

800

MHz

dBm

Preamp limiting

-40

Input Overload

VCO Sensitivity (dF/dV)

Refer to Fig. 1

39 MHz/V

Refer to Fig. 1 with13.5MHz p-p

deviation

VCO linearity

VCO Supply Stability

See note 5

2.0

MHz/V

KHz/°C

VCO Temperature Stability

See note 5

Differential loop filter

Single ended loop filter

0.5

0.25

Phase Detector Gain

V/rad

Loop Amplifier Input Impedance

Loop Amplifier Output Impedance

Loop Amplifier Open Loop Gain

Loop Amplifier Gain Bandwidth Product

Loop Amplifier Output Swing

R_IN

450 570 700

Ω

R_OUT(LOOP)

B_W

240

1.2

MHz

Vp-p

Ω

Video Drive Output Impedance

R_OUT(VIDEO)

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ELECTRICAL CHARACTERISTICS(Cont.)

PARAMETER

SYMBOL

CONDITIONS

MIN TYP MAX UNIT

VIDEO DRIVE

Luminance Nonlinearity

Differential Gain

1KΩ load, See note 3 and 4

75KΩ load, See note 3 and 4

See notes 1, 3 and 4

1KΩ load, See note 2 and 4

1KΩ load, See note 3 and 4

Maximum load voltage drop 2V

1.9

0.5

1.0

2.5

Degree

Differential Phase

Intermodulation

Signal/noise

Tilt

-40

0.3

0.4

Baseline Distortion

AGC Output Current

I_OUT

I_BIAS

400

250

400

µA

AGC Bias Current

µA

400µA gives 1.5V deadband

window

µA

AFC Window Current

AFC Charge Pump Current

AFC Leakage Current

µA

I_LEAK

With charge pump disabled

AFC Output Saturation Voltage

V_O(SAT)AFC output enabled

0.4

Note 1. Input modulation’s product f 1 at 4.43MHz, 13.5MHz p–p deviation and f 2 at 6MHz p–p deviation, (PAL

chroma and sound subcarriers).

2. To output rms noise in 6MHz bandwidth with no input modulation, ratio of output video signal with input

modulation at 1MHz, 13.5MHz p–p deviation.

3. Output voltage is 600mV pk–pk and input test signal pre–emphasised video 13.5MHz p–p deviation.

4. See page 4

5. Assuming ambient temperature of +20°C and operating frequency of 479.5MHz set with V_CC@ 5.0V. Only

applies to application shown in Fig. 1 also refer to Fig. 4.

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L2572

LINEAR INTEGRATED CIRCUIT

APPLICATION CIRCUIT

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FUNCTIONAL DESCRIPTION

The UTC L2572 as optimized for application in satellite receiver systems and requiring a minimum external

component count is a wideband PLL FM demodulator. It includes all the elements required to construct a phase

locked loop circuit, with the exception of an AFC detector circuit for generation of error signal to correct for any

frequency drift in the outdoor unit local oscillator, and tuning components for the local oscillator contains a block

diagram and Fig. 1 contains the typical application.

Fig. 2-1 contains the internal pin connections

In applications the second satellite IF frequency of typically 479.5 or 402MHz is fed to the RF preamplifier normally,

which depending on application and layout has a working sensitivity of typically -40 dBm. An RF level detect circuit,

which generates an AGC signal that can be used for controlling the gain of the IF amplifier stages is contained in the

preamplifier, so it can be maintaining a fixed level to the RF input of the UTC L2572, for optimum threshold

performance. The AGC circuit’s bias point can be adjusted to cater for device input power and variation in AGC line

voltage requirement. Fig. 5 shows the typical AGC curves are shown in. That the device is recommended that be

operated with an input signal between -30 and -35dBm. That can ensure optimum linearity and threshold

performance, and when over the typical sensitivity of -40dBm can give a good safety margin.

The preamplifier’s output is fed to the mixer section which is of balanced design for low radiation. In this stage the

RF signal is mixed with which is generated by an on–board oscillator, the local oscillator frequency. The oscillator

block is optimized for high linearity over the normal deviation range and uses an external varactor tuned sustaining

network. Fig. 3 contains a typical frequency versus voltage characteristic for the oscillator. Fig.4 shows the typical

stability that he loop output is designed to compensate for first order temperature variation effects.

The mixer’s output is then fed to the loop amplifier around which feedback is applied to effect loop transfer

characteristic. Feedback could be applied either in single ended or differential mode; both modes should give the

same loop response if the appropriate phase detector gains are assumed in calculating loop filters.

The loop amplifier drives a 75Ω output impedance buffer amplifier, which could be connected to a 75Ω load and

used to drive a high input impedance stage giving greater linearity and approximately 6dB higher demodulated signal

output level too.

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LINEAR INTEGRATED CIRCUIT

INTERNAL CIRCUITS

V_CC

AGC Bias

V_REF:2.7V

V_REF:2V

AGC Output

Fig. 2-1 AGC Output

Fig. 2-2 AGC Bias Adjust

AFC WINDOW

V_REF:36V

2X1500

RF Input

V_REF:1.6V

Fig. 2-4 AFC Window Adjust

Fig. 2-3 RF Input

V_CC

AFC Pump

Video +

Video -

10K

AFC OUTPUT

330

2mA

Fig. 2-5 AFC Output Stage

Fig. 2-6 Video Amp Output

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INTERNAL CIRCUITS(Cont.)

From Phase Detector

2x570

V_REF:1.2V

2X5K

VIDEO

FEEDBACK +

OSCILLATOR +

OSCILLATOR -

VIDEO

FEEDBACK -

Fig. 2-7 Local Oscillator

Fig. 2-8 Video amp feedback inputs

V_CC

Output

Video

105

4mA

Fig. 2-9 Video Output Drive

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2.0

1.5

1.0

AGC Bias Resistor 5.1K

AGC Bias Current 297 A

AGC Load Resistor 3.9K

AGC Bias Resistor 10.5K

AGC Bias Current 150 A

AGC Load Resistor 4.7K

0.5

AGC Bias Resistor 32K

AGC Bias Current 52 A

AGC Load Resistor 10K

-70 -60 -50 -40 -30 -20 -10

RF Input Level (dBm) Unmodulated

V_CC= 5.0 V

Fig.5 AGC Output Voltage for Differing Values of AGC Bias Resistor

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LINEAR INTEGRATED CIRCUIT

DESIGN OF PLL LOOP PARAMETERS

The UTC L2572 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;

τ₁= C1.R1

τ₂= C1.R2

and

K₀K_D

τ₁=

ω_n²

2ζ

τ ₂=

ω_n

where:

K₀is the VCO gain in radian seconds per volt

K_Dis the phase detector gain in volts per radian

ω_nis the natural loop bandwidth

ξ is the loop damping factor

R1 is loop amplifier input impedance

Note: K₀is dependant on sensitivity of VCO used.

K_D= 0.25V/rad single ended, 0.5V/rad differential

From these factors the loop 3dB bandwidth can be determined from the following expression;

ω₃²_dB= ω_n²(2ζ ²+1) ± ω_n²(2ζ ²+1)²+1

Which approximates to ω_3dB= 2ω_nwhen ζ =

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LINEAR INTEGRATED CIRCUIT

AFC FACILITY

An analog frequency error detect circuit, which generates DC voltage proportional to the integral of frequency error

is contained in UTC L2572.As the incident RF is high then the AFC voltage increases, as low then the voltage

decreases. ADC converts the AFC voltage can then be an to be read by the micro controller for frequency fine

tuning.

Around the aligned frequency the AFC detect circuit contains a deadband centre. From zero window to

approximately 25MHz width assuming an oscillator dF/dV of 15MHz/V the deadband can be adjusted. The AFC

voltage does not integrate if the incident RF is within this window, except by component leakage.

With reference to Fig. 6; the demodulated video is fed to a dual comparator which can be compared with two

reference voltages in normal operation, corresponding to the extremes of the deadband, or window. These voltages

are variable and the window adjust input can set it.

Two digital outputs corresponding to voltages above or below the voltage window, or frequency above or below

deadband can be produced by the comparators. These digital control signals can control a complimentary current

source pump. The current signals are then fed to an amplifier’s input. it is arranged as an integrator, so integrating

the pulses into a DC voltage.

Both the current source and sink are disabled if the frequency is correctly aligned, therefore the DC output voltage

can be constant. Due to component leakage there will be a small drift; the maximum drift can be calculated from

here:

Vcc

where

I =

C = C_EXT

2500.C

R_EXT

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LINEAR INTEGRATED CIRCUIT

UTC assumes no responsibility for equipment failures that result from using products at values that

exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or

other parameters) listed in products specifications of any and all UTC products described or contained

herein. UTC products are not designed for use in life support appliances, devices or systems where

malfunction of these products can be reasonably expected to result in personal injury. Reproduction in

whole or in part is prohibited without the prior written consent of the copyright owner. The information

presented in this document does not form part of any quotation or contract, is believed to be accurate

and reliable and may be changed without notice.

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L2572 [UTC]

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