ds8907 National Semiconductor Corporation, ds8907 Datasheet

ds8907

Manufacturer Part Number

ds8907

Description

Phase-locked Loop Frequency Synthesizer

Manufacturer

National Semiconductor Corporation

Datasheet

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C 1995 National Semiconductor Corporation

DS8907 AM FM Digital

Phase-Locked Loop Frequency Synthesizer

General Description

The DS8907 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 an 18-bit shift reg-

ister 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 25 kHz reference signal for FM and a 10 kHz

reference signal for AM One of these reference signals is

selected by the data from the controller for use by the

phase comparator

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 20-bit data stream the first 2 bits ad-

dress the device permitting other devices to share the same

bus Of the remaining 18-bit data word the next 13 bits are

used for the PLL divide code The remaining 5 bits are con-

nected via latches to output pins These 5 bits can be used

to drive radio functions such as gain mute FM AM and

stereo only These outputs are open collector Bit 16 is used

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

select between the 10 kHz and 25 kHz reference A high

level at bit 16 indicates FM and a low level indicates AM

The PLL consists of a 13-bit programmable I

ECL phase comparator an ECL dual modulus (p p

scaler and a high speed charge pump The programma-

Connection Diagram

TRI-STATE is a registered trademark of National Semiconductor Corporation

TL F 7511

L divider an

Dual-In-Line Package

1) pre-

Top View

ble divider divides by (N

into the shift register (bits 1 – 13 after address) It is clocked

by the AM input via an ECL

at frequencies up to 15 MHz while the FM input works up to

120 MHz The AM band is tuned with a frequency resolution

of 10 kHz and the FM band is tuned with a resolution of

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

can be driven directly by the VCO through a capacitor The

ECL phase comparator produces very accurate resolution

of the phase difference between the input signal and the

reference oscillator The high speed charge pump consists

of a switchable constant current source (

switchable constant current sink (

quency is low the charge pump will source current and sink

current if the VCO frequency is high When using an AFC

the charge pump output may be forced into TRI-STATE by

applying a low level to the charge pump enable input

A separate V

oscillator and reference chain to provide controller clocking

frequencies when the balance of the PLL is powered down

Features

Uses inexpensive 4 MHz reference crystal

thesis at FM frequencies

FM resolution of 25 kHz allows usage of 10 7 MHz ce-

ramic filter distribution

Serial data entry for simplified control

50 Hz output for ‘‘time-of-day’’ reference driven from

separate low power V

5-open collector buffered outputs for controlling various

radio functions

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

cal) hysteresis

capability greater than 120 MHz allows direct syn-

prescaler from the FM input The AM input will work

CCM

pin (typically drawing 1 5 mA) powers the

TL F 7511 – 1

CCM

1) N being the number loaded

See NS Package Number

Order Number DS8907N

prescaler or through a

0 3 mA) If the VCO fre-

RRD-B30M105 Printed in U S A

N20A

0 3 mA) and a

July 1986

Related parts for ds8907

ds8907 Summary of contents

Page 1

... DS8907 AM FM Digital Phase-Locked Loop Frequency Synthesizer General Description The DS8907 is a PLL synthesizer designed specifically for use radios It contains the reference oscillator a phase comparator a charge pump a 120 MHz ECL I dual modulus programmable divider and an 18-bit shift reg- ister latch for serial data entry The device is designed to ...

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

... Note 3 All currents into device pins shown as positive out of device pins as negative all voltages referenced to ground unless otherwise noted All values shown as max or min on absolute value basis Schematic Diagrams (DS8907 AM FM PLL typical Input Output Schematics 7511 – 7511 – 7511 – ...

Page 4

... Timing diagrams are not drawn to scale Scale within any one drawing may not be consistent and intervals are defined positive as drawn SERIAL DATA ENTRY INTO THE DS8907 Serial information entry into the DS8907 is enabled by a low level on the ENABLE input One binary bit is then accepted ...

Page 5

Typical Application Electronically Tuned Radio Controller System Direct Drive LED 7511 – 12 ...

Page 6

Logic Diagram AM FM PLL Synthesizer (Serial Data 20-Pin Package) Sections operating from V supply CCM Address ( 7511 – 13 ...

Page 7

7 ...

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 DS8907N NS Package Number N20A 2 A critical component is any component of a life ...

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