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Ordering number:ENN2208A
Monolithic Linear IC
LA7770
FSK Receiver for CATV Use
Overview
The LA7770 is a CATV-oriented wide-band FSK (frequency shift keying) receiver IC encapsulated in a DIP20S package that incorporates the functions required to demodulate scramble decoding data (i. e., the oscillator, mixer, limiting IF amplifier, squelcher, and data shaper functions).
Package Dimensions
unit:mm 3021C-DIP20
[LA7770]
24.0 20 11
Functions
* Mixer. * Limiting IF amplifier. * Squelch meter drive. * Oscillator. * Quadrature detector. * Data shaper.
(0.57) 2.54 0.5 1.2
Specifications
Maximum Ratings at Ta = 25C
Parameter Maximum supply voltage Maximum flow-out current Allowable power dissipation Operating temperature Storage temperature Symbol VCC4 max VCC6 max I18 max Pd max Topr Tstg Conditions Ratings 15 15 3 Unit V V mA mW
0.51min (3.25) 3.3 3.9max
* High limiting sensitivity. * Incorporating a common-collector oscillator enables LC, crystal, or SAW-R (surface acoustic wave resonator) operated oscillations, as required by application.
1 1.0
10
SANYO : DIP20
Ta65C
770 -20 to +85 -55 to +125
C C
Operating Conditions at Ta = 25C
Parameter Operating voltage range Comparator input voltage range Symbol VCC4 VCC6 V16, V19 Conditions Ratings 9 to 12 9 to 12 2V to (VCC-2V) Unit V V V
Any and all SANYO products described or contained herein do not have specifications that can handle applications that require extremely high levels of reliability, such as life-support systems, aircraft's control systems, or other applications whose failure can be reasonably expected to result in serious physical and/or material damage. Consult with your SANYO representative nearest you before using any SANYO products described or contained herein in such applications. SANYO 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 SANYO products described or contained herein.
SANYO Electric Co.,Ltd. Semiconductor Company
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN
13101TN (KT)/O0695TH (KOTO)/D088MO/O127TA, TS No.2208-1/7
0.25
Features
7.62 6.4
LA7770
Operating Characteristics at Ta = 25C
Parameter Quiescent current Circuit current Mixer input capacitance Mixer input resistance Mixer voltage gain -3dB limiting sensitivity S/N Total harmonic distortion Demodulation output AM rejection Meter drive Squelch threshold voltage Data shaper input current Output saturation voltage Duty Symbol Icco ICC ci ri Vgm Vi S/N THD Vo AMR ID V14TH I16 V18(sat) | TD | SQ-off SQ-on 100MHz 100MHz RL=300, 106.5M 10.7M F=75kHz dev, at 1kHz F=75kHz dev, at 1kHz F=75kHz dev, at 1kHz F=75kHz dev, at 1kHz AM : 30% at 1kHz 300A 600A DC DC I18=2mA f=14kHz 47 300 47 5 0.8 9 Conditions Ratings min 22 23.0 typ 29 30.5 7 680 12 25 55 0.6 440 55 12 1.5 0.7 0.1 2.5 20 2.2 3.0 0.7 5.0 2 15 31 max 37 39.0 Unit mA mA pF dB dB/V dB % dB A/dB V A V % 600 mVrms
Equivalent Circuit Block Diagram
No.2208-2/7
LA7770
LA7770 Dynamic Behavior and Cautions on Designing (1) Mixer A double differential type mixer is employd with its input circuit configured as shown in Fig. 1, where the input signal is mixed with the oscillator output by its double differential circuit. The mixed signal will be output from its open collector pin 5.
Fig. 1 Caution a. Since an internal bias is applied to the input pin (pin 20), be sure to provide a DC blocking capacitor as shown in Fig. 2. b. Connect the decoupling capacitor across pins 4 and 1 with the shortest possible wiring.
Fig. 2
(2) Oscillator A common-collector oscillator is employed as shown in Fig. 3, and enables the LC, crystal, or SAW-R operated oscillations.
Fig. 3
No.2208-3/7
LA7770
(3) IF Limiting Amplifier The limiter amplifier employed is made up of DC feedback-provided 6-stage direct-coupled differential amplifiers. Simplified, its circuit is represented in Fig. 4 below.
Fig. 4 Feedback gain (AV) will be AV=
A = 1+A
1 1 + A
1
1 where feedback depth = V2 = V1 1+ (CR)2 so that the decoupling capacitor C should be made sufficiently large in capacitance within the operating frequency band to achieve its low impedance.
(4) Quadrature Detector The quadrature detector converts a frequency-modulated signal into a phase-modulated one by passing it through a phase shifter, and then demodulates it by converting it again into voltage with its phase detector. The quadrature detector block of the LA7770 is configured as shown in Fig. 5 below.
Fig. 5 Phase Shifter The phase shifter is an important element of the quadrature detector, and it dictates the detection characteristics of the latter. The following phase-shifter-related parameters may be cited. 1. Demodulation output ........... Chiefly QL 2. Distortion Factor .................. Phase shifter linearity and symmetry of S curve * While the phase shifting linearity may be enhanced with a single tuning circuit by lowering its QL and broadening its frequency band, its demodulation output will also be lowered in the process.
Fig. 6
No.2208-4/7
LA7770
In the Fig. 6 phase shifter, 1 1 jC2+ +jwL R 1 + jC1 1 1 jC2+ +jwL R
V2 = V1
=
1 1 2L (C1+C2)-1 -j jCR 2LC1
Requirements to achieve a 90 phase shift will be : 2L (C1+C2)=1 = 1 L (C1+C2) 1 = 1 2L (C1+C2)
V2 = V1

2L (C1+C2)-1 2LC1
2
+
1 jC1R
2
At the tuning point : V2 = V1 1 1 C1R
2
=C1R
(5) Meter Drive and Squelch A forward bias is provided to the meter drive dedicated detector, to enable its detector diode to detect low-level signals. In addition, a bias canceler is also provided to eliminate the offsetting current in a no-signal mode created by the forward bias. Furthermore, to broaden the linear operating range, signals are fetched from the 3rd and 5th stage outputs of the limiter amplifier, for composition together after level detection.
Fig. 7
No.2208-5/7
LA7770
The composite current after the level detection flows out from pin 14, and after its being converted to a voltage by an externally connected circuit, will detremine V1 of the comparator. The squelch circuit may be provided with hysteresis by providing a resistor feedback from pin 15 to pin 14.
Fig. 8 (6) Data Shaper The data shaper is a high-impedance input differential amplifier that provides an open-collector output. It serves to facilitate the design for matching with a following stage (such as a CPU).
Fig. 9
No.2208-6/7
LA7770
Specifications of any and all SANYO products described or contained herein stipulate the performance, characteristics, and functions of the described products in the independent state, and are not guarantees of the performance, characteristics, and functions of the described products as mounted in the customer's products or equipment. To verify symptoms and states that cannot be evaluated in an independent device, the customer should always evaluate and test devices mounted in the customer's products or equipment. SANYO Electric Co., Ltd. strives to supply high-quality high-reliability products. However, any and all semiconductor products fail with some probability. It is possible that these probabilistic failures could give rise to accidents or events that could endanger human lives, that could give rise to smoke or fire, or that could cause damage to other property. When designing equipment, adopt safety measures so that these kinds of accidents or events cannot occur. Such measures include but are not limited to protective circuits and error prevention circuits for safe design, redundant design, and structural design. In the event that any or all SANYO products(including technical data,services) described or contained herein are controlled under any of applicable local export control laws and regulations, such products must not be expor ted without obtaining the expor t license from the authorities concerned in accordance with the above law. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or any information storage or retrieval system, or otherwise, without the prior written permission of SANYO Electric Co., Ltd. Any and all information described or contained herein are subject to change without notice due to product/technology improvement, etc. When designing equipment, refer to the "Delivery Specification" for the SANYO product that you intend to use. Information (including circuit diagrams and circuit parameters) herein is for example only ; it is not guaranteed for volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied regarding its use or any infringements of intellectual property rights or other rights of third parties.
This catalog provides information as of January, 2001. Specifications and information herein are subject to change without notice.
PS No.2208-7/7

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