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LTC6905

6905fd

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

17MHz to 170MHz

Resistor Set SOT-23 Oscillator

The LTC

6905 precision, programmable silicon oscilla-

tor is easy to use and occupies very little board space. It

requires only a single resistor to set the output frequency

from 17MHz to 170MHz with a typical frequency error of

0.5% or less.

The LTC6905 operates with a single 2.7V to 5.5V power

supply and provides a rail-to-rail, 50% duty cycle square

wave output. The CMOS output driver ensures fast rise/fall

times and rail-to-rail switching. Operation is simple: A

single resistor, R

SET

, between 10k to 25k is used to set

the frequency, and an internal three-state divider (DIV

input) allows for division of the master clock by 1, 2 or 4,

providing three frequencies for each R

SET

value.

The LTC6905 features a proprietary feedback loop that

linearizes the relationship between R

SET

and frequency,

eliminating the need for tables to calculate frequency. The

oscillator can be easily programmed using the simple

formula outlined below:

MHz k

MHz

N Open

OSC

SET

⎛

⎝

⎜

⎞

⎠

⎟

⎧

⎨

⎪

⎩

⎪

168 5 10

.•

.•,

DIV Pin V

DIV Pin

DIV Pin GND

For higher accuracy, ﬁ xed frequency versions that

include an internal frequency-setting resistor, see the

LTC6905-XXX Series data sheet

Typcial Distribution of Frequency Error, T

= 25°C

One External Resistor Sets the Frequency

Fast Start-Up Time: 100μs Typical

Frequency Range: 17MHz to 170MHz

Frequency Error ±0.5% Typ 17MHz to 170MHz

= 0°C to 70°C, Over All Settings)

±20ppm/°C Temperature Stability

Rise Time: 0.5ns, C

= 5pF

Timing Jitter: 7.2ps RMS at 170MHz

50% ±2.5% Duty Cycle

6mA Typical Supply Current, f

OSC

= 100MHz

CMOS Output Drives 500Ω Load (V

= 3V)

Operates from a Single 2.7V to 5.5V Supply

Low Proﬁ le (1mm) ThinSOT

™

Package

High Frequency Precision Oscillator

High Speed Data Bus Clock

Fixed Crystal Oscillator Replacement

Ceramic Oscillator Replacement

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

ThinSOT is a trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected by U.S. Patents including 6614313, 6342817.

% ERROR

–0.5

UNITS

NOTE: RESISTOR, R

SET

, TOLERANCE WILL ADD

TO THE FREQUENCY ERROR

–0.3 –0.1 0.1 0.3

6905 TA02

0.5

= 3V

SET

= 12k

DIV = 1

17.225MHz ≤ f

OSC

≤ 170MHz

10k ≤ R

SET

≤ 25k

0.1μF

6905 TA01

GND

LTC6905

SET

OUT

DIV

OPEN

÷2

÷1

÷4

Basic Connection

Summary of content (12 pages)

PAGE 1
LTC6905 17MHz to 170MHz Resistor Set SOT-23 Oscillator FEATURES DESCRIPTION n The LTC®6905 precision, programmable silicon oscillator is easy to use and occupies very little board space. It requires only a single resistor to set the output frequency from 17MHz to 170MHz with a typical frequency error of 0.5% or less. n n n n n n n n n n The LTC6905 features a proprietary feedback loop that linearizes the relationship between RSET and frequency, eliminating the need for tables to calculate frequency.
PAGE 2
LTC6905 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Supply Voltage (V+) to GND .........................– 0.3V to 6V DIV to GND .................................... – 0.3V to (V+ + 0.3V) SET to GND .................................... – 0.3V to (V+ + 0.3V) Output Short-Circuit Duration (Note 6) ........... Indeﬁnite Operating Temperature Range (Note 7) LTC6905C, I .........................................– 40°C to 85°C LTC6905H ..........................................– 40°C to 125°C LTC6905MP .
PAGE 3
LTC6905 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full speciﬁed temperature range, otherwise speciﬁcations are at TA = 25°C or as noted. V+ = 2.7V to 5.5V, RL = 15k, CL = 5pF, Pin 4 = V+ unless otherwise noted. All voltages are with respect to GND. SYMBOL Δf PARAMETER Frequency Accuracy (Notes 2, 9) CONDITIONS MIN V+ = 2.7V, 17.225MHz < f < 170MHz V+ = 5V, 17.225MHz < f < 170MHz LTC6905CS5 V+ = 2.7V, 17.225MHz < f < 170MHz V+ = 5V, 17.
PAGE 4
LTC6905 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full speciﬁed temperature range, otherwise speciﬁcations are at TA = 25°C or as noted. V+ = 2.7V to 5.5V, RL = 15k, CL = 5pF, Pin 4 = V+ unless otherwise noted. All voltages are with respect to GND. SYMBOL VOL tr , tf PARAMETER CONDITIONS Low Level Output Voltage (Note 4) V+ = 5.5V, Pin 4 = 0V MIN IOL = 1mA IOL = 4mA V+ = 2.7V, Pin 4 = 0V IOL = 1mA IOL = 4mA TYP MAX UNITS l l 0.05 0.2 0.25 0.
PAGE 5
LTC6905 TYPICAL PERFORMANCE CHARACTERISTICS ROUT vs V+ Jitter vs Frequency 45 0.8 40 35 30 25 20 15 10 ÷4 ÷2 PERCENTAGE ERROR (%) 1.00 PEAK-TO-PEAK JITTER (%) OUTPUT RESISTANCE (Ω) Frequency vs Temperature 1.0 1.20 ÷1 0.80 0.60 0.40 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 0.20 5 –0.8 0 0 2.5 3 3.5 4 4.5 SUPPLY VOLTAGE (V) 5 5.5 0 20 40 60 80 100 120 140 160 180 FREQUENCY (MHz) –1.
PAGE 6
LTC6905 BLOCK DIAGRAM 1 VRES = 1V ±5% (V+ – VSET) V+ PROGRAMMABLE DIVIDER (÷1, 2 OR 4) + RSET GAIN = 1 IRES 3 SET – fOSC = fMO N OUT 5 MASTER OSCILLATOR V+ DIVIDER SELECT 15μA + – 2 GND – VBIAS IRES DIV THREE-STATE INPUT DETECT + 4 15μA GND 6905 BD 6905fd 6
PAGE 7
LTC6905 THEORY OF OPERATION A resistor RSET , connected between the V+ and SET pins, “locks together” the voltage (V+ – VSET) and current, IRES, variation. This provides the LTC6905’s high precision. The master oscillation frequency reduces to: 168.5MHz • 10k Ω fMO = + 1.5MHz RSET To extend the output frequency range, the master oscillator signal is divided by 1, 2 or 4 before driving OUT (Pin 5).
PAGE 8
LTC6905 APPLICATIONS INFORMATION SELECTING THE DIVIDER SETTING AND RESISTOR The LTC6905’s master oscillator has a frequency range spanning 68.9MHz to 170MHz. A programmable divider extends the frequency range from 17.225MHz to 170MHz. Table 1 describes the recommended frequencies for each divider setting. Note that the ranges overlap; at some frequencies there are two divider/resistor combinations that result in the same frequency.
PAGE 9
LTC6905 APPLICATIONS INFORMATION JITTER AND DIVIDE RATIO At a given output frequency, a higher master oscillator frequency and a higher divide ratio will result in lower jitter and higher power supply dissipation. Indeterminate jitter percentage will decrease by a factor of slightly less than the square root of the divider ratio, while determinate jitter will not be similarly attenuated. Please consult the speciﬁcation tables and Jitter vs Frequency graph showing jitter at various divider ratios.
PAGE 10
LTC6905 APPLICATIONS INFORMATION ALTERNATIVE METHODS OF SETTING THE OUTPUT FREQUENCY OF THE LTC6905 The LTC6905 may be programmed by any method that sources a current into the SET pin (Pin 3). The accuracy of the programming is best with a simple resistor because the LTC6905 takes into account both the voltage at the SET pin and the current into the SET pin when generating the output frequency.
PAGE 11
LTC6905 PACKAGE DESCRIPTION S5 Package 5-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1635) 0.62 MAX 0.95 REF 2.90 BSC (NOTE 4) 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 TYP 5 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4.
PAGE 12
LTC6905 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1799 1kHz to 33MHz ThinSOT Oscillator Single Output, High Frequency Operation LTC6900 1kHz to 20MHz ThinSOT Oscillator Single Output Lower Power LTC6902 Multiphase Oscillator with Spread Spectrum Modulation LTC6903/LTC6904 1kHz to 68MHz Serial Port Programmable Oscillator 2-, 3- or 4-Phase Outputs 3-Wire or I2C™ Programmable LTC6905-XXX Series Fixed Frequency LTC6905 High Accuracy, No External Resistor LTC6906 Micropower, 10kHz to 1