LTC6903/LTC6904

1

69034fa

FREQUENCY ERROR (%)

–1.0

40

30

20

10

0

–0.5

6903 TA01b

0

0.5

1.0

f = 1039Hz

443

UNITS

TESTED

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

s

1kHz to 68MHz Square Wave Output

s

0.5% (Typ) Initial Frequency Accuracy

s

Frequency Error <1.1% Over All Settings

s

10ppm/

°C Typical Frequency Drift Over

Temperature

s

0.1% Resolution

s

s

2.7V to 5.5V Single Supply Operation

s

Jitter <0.4% Typical 1kHz to 8MHz

s

Interface

s

Output Enable Pin

s

–40

°C to 125°C Operation

s

MS8 Package

1kHz - 68MHz Serial

Port Programmable Oscillator

The LTC

digital frequency sources providing a precision frequency

from 1kHz to 68MHz, set through a serial port. The

LTC6903/LTC6904 require

no external components other

than a power supply bypass capacitor, and they operate

over a single wide supply range of 2.7V to 5.5V.

The LTC6903/LTC6904 feature a proprietary feedback

loop that linearizes the relationship between digital control

setting and frequency, resulting in a very simple frequency

setting equation:

f

Hz

DAC

kHz

f

MHz

OCT

=









<<

2

2078

2

1024

168

•

()

–

;

Where OCT is a 4-bit digital code and DAC is a 10-bit digital

code.

The LTC6903 is controlled by a convenient SPI compatible

serial interface. The LTC6904 uses an industry standard

, LTC and LT are registered trademarks of Linear Technology Corporation.

s

Precision Digitally Controlled Oscillator

s

Power Management

s

Direct Digital Frequency Synthesis (DDS)

Replacement

s

Replacement for DAC and VCO

s

Switched Capacitor Filter Clock

PIC16F73

MICROCONTROLLER

RC2/CCP1

RC5/SDO

RC3/SCK/SCL

LTC6903

0.01

µF

GND

SDI

SCK

SEN

POWER-UP CLOCK

FREQUENCY IS 1039Hz

5V

10

Ω

10k

5V

OE

CLK

6903 TA01

CLK

OSC2/CLKOUT

OSC1/CLKIN

1

µF

0.1

µF

A Microcontroller Controlling Its Clock

LTC6903 Frequency Error

Distribution

U.S. Patent Numbers 6342817 and 6614313.