DS8906N NSC [National Semiconductor], DS8906N Datasheet

DS8906N

Manufacturer Part Number

DS8906N

Description

AM/FM Digital Phase-Locked Loop Synthesizer

Manufacturer

NSC [National Semiconductor]

Datasheet

1.DS8906N.pdf (8 pages)

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C 1995 National Semiconductor Corporation

DS8906 AM FM Digital Phase-Locked Loop Synthesizer

General Description

The DS8906 is a PLL synthesizer designed specifically for

use in AM FM radios It contains the reference oscillator a

phase comparator a charge pump a 120 MHz ECL I

dual modulus programmable divider and a 20-bit shift regis-

ter latch for serial data entry The device is designed to

operate with a serial data controller generating the neces-

sary division codes for each frequency and logic state infor-

mation for radio function inputs outputs

The Colpitts reference oscillator for the PLL operates at 4

MHz A chain of dividers is used to generate a 500 kHz

clock signal for the external controller Additional dividers

generate a 12 5 kHz reference signal for FM and a 500 Hz

reference signal for AM SW One of these reference signals

is selected by the data from the controller for use by the

phase comparator Additional dividers are used to generate

a 50 Hz timing signal used by the controller for ‘‘time-of-

day’’

Data is transferred between the frequency synthesizer and

the controller via a 3 wire bus system This consists of a

data input line an enable line and a clock line When the

enable line is low data can be shifted from the controller

into the frequency synthesizer When the enable line is tran-

sitioned from low to high data entry is disabled and data

present in the shift register is latched

From the controller 22-bit data stream the first 2 bits ad-

dress the device permitting other devices to share the same

bus Of the remaining 20-bit data word the next 14-bits are

used for the PLL divide code The remaining 6 bits are con-

nected via latches to output pins These 6 bits can be used

to drive radio functions such as gain mute FM AM LW and

SW only These outputs are open collector Bit 18 is used

internally to select the AM or FM local oscillator input and to

select between the 500 Hz and 12 5 kHz reference A high

level at bit 18 indicates FM and a low level indicates AM

The PLL consists of a 14-bit programmable I

ECL phase comparator an ECL dual modulus (p p

prescaler and a high speed charge pump The programma-

ble divider divides by (N

into the shift register (bits 1–14 after address) It is clocked

by the AM input via an ECL

63 64 prescaler from the FM input The AM input will work

at frequencies up to 8 MHz while the FM input works up to

120 MHz The AM band is tuned with a frequency resolution

of 500 Hz and the FM band is tuned with a resolution of 12 5

kHz The buffered AM and FM inputs are self-biased and

can be driven directly by the VCO thru a capacitor The ECL

phase comparator produces very accurate resolution of the

phase difference between the input signal and the reference

oscillator

TRI-STATE is a registered trademark of National Semiconductor Corp

1) N being the number loaded

TL F 5775

7 8 prescaler or through a

L divider an

The high speed charge pump consists of a switchable con-

stant current source (

current sink (

charge pump will source current and sink current if the VCO

frequency is high

A separate V

oscillator and reference chain to provide controller clocking

frequencies when the balance of the PLL is powered down

Features

Connection Diagram

Uses inexpensive 4 MHz reference crystal

thesis at FM frequencies

FM resolution of 12 5 kHz allows usage of 10 7 MHz

ceramic filter distribution

Serial data entry for simplified control

50 Hz output for ‘‘time-of-day’’ reference with separate

low power supply (V

6-open collector buffered outputs for band switching

and other radio functions

Separate AM and FM inputs AM input has 15 mV (typi-

cal) hysteresis

capability greater than 120 MHz allows direct syn-

CCM

See NS Package Number N20A

0 3 mA) If the VCO frequency is low the

Order Number DS8906N

pin (typically drawing 1 5 mA) powers the

Dual-In-Line Package

CCM

0 3 mA) and a switchable constant

Top View

)

RRD-B30M105 Printed in U S A

TL F 5775 – 1

July 1986

Related parts for DS8906N

DS8906N Summary of contents

Page 1

... Y and other radio functions Separate AM and FM inputs AM input has 15 mV (typi- Y cal) hysteresis Connection Diagram Dual-In-Line Package 2 L divider Top View Order Number DS8906N See NS Package Number N20A July 1986 ) TL F 5775 – 1 RRD-B30M105 Printed ...

Page 2

Absolute Maximum Ratings If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Voltage (V ) CC1 (V ) CCM Input Voltage Output Voltage DC Electrical Characteristics Symbol Parameter V ...

Page 3

AC Electrical Characteristics Symbol Parameter t Minimum Time After ENABLE EN1CLK Goes High Before an Unused Positive CLOCK Edge May Occur t Minimum CLOCK High CLKH Pulse Width t Minimum CLOCK Low CLKL Pulse Width t Minimum DATA Setup Time ...

Page 4

Schematic Diagrams (DS8906 AM FM PLL Typical Input Output Schematics) (Continued 5775– 7 Timing Diagrams AM FM Frequency Synthesizer (Scan Mode) Timing diagrams are not drawn to scale Scale within any one drawing may not be consistent and ...

Page 5

Applications Information SERIAL DATA ENTRY INTO THE DS8906 Serial information entry into the DS8906 is enabled by a low level on the ENABLE input One binary bit is then accepted from the DATA input with each positive transition of the ...

Page 6

Typical Application Electronically Tuned Radio Controller System Direct Drive LED 5775– 12 ...

Page 7

Logic Diagram Sections operating from V supply CCM Address ( PLL Synthesizer 5775 – 13 ...

Page 8

... National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications Molded Dual-In-Line Package (N) Order Number DS8906N NS Package Number N20A 2 A critical component is any component of a life ...

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