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PDF LTC6905 Data sheet ( Hoja de datos )
| Número de pieza | LTC6905 | |
| Descripción | 17MHz to 170MHz Resistor Set SOT-23 Oscillator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
n One External Resistor Sets the Frequency
n Fast Start-Up Time: 100μs Typical
n Frequency Range: 17MHz to 170MHz
n Frequency Error ±0.5% Typ 17MHz to 170MHz
(TA = 0°C to 70°C, Over All Settings)
n ±20ppm/°C Temperature Stability
n Rise Time: 0.5ns, CL = 5pF
n Timing Jitter: 7.2ps RMS at 170MHz
n 50% ±2.5% Duty Cycle
n 6mA Typical Supply Current, fOSC = 100MHz
n CMOS Output Drives 500Ω Load (VS = 3V)
n Operates from a Single 2.7V to 5.5V Supply
n Low Profile (1mm) ThinSOT™ Package
APPLICATIONS
n High Frequency Precision Oscillator
n High Speed Data Bus Clock
n Fixed Crystal Oscillator Replacement
n 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.
LTC6905
17MHz to 170MHz
Resistor Set SOT-23 Oscillator
DESCRIPTION
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, RSET, 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 RSET value.
The LTC6905 features a proprietary feedback loop that
linearizes the relationship between RSET and frequency,
eliminating the need for tables to calculate frequency. The
oscillator can be easily programmed using the simple
formula outlined below:
⎧1, DIV Pin = V +
fOSC
=
⎛ 168.5MHz •10kΩ
⎝⎜ RSET
+
1.5MHz⎞⎠⎟
•
1,
N
N
=
⎨⎪2, DIV
⎩⎪4, DIV
Pin
Pin
=
=
Open
GND
For higher accuracy, fixed frequency versions that
include an internal frequency-setting resistor, see the
LTC6905-XXX Series data sheet.
TYPICAL APPLICATION
Basic Connection
5V
10k ≤ RSET ≤ 25k
0.1μF
17.225MHz ≤ fOSC ≤ 170MHz
1 V+
5
OUT
2 LTC6905
GND
34
SET DIV
5V
÷1
÷2
OPEN
6905 TA01
÷4
Typcial Distribution of Frequency Error, TA = 25°C
60 V+ = 3V
RSET = 12k
50 DIV = 1
40
30
20
10
0
–0.5 –0.3
–0.1 0.1
% ERROR
0.3 0.5
6905 TA02
NOTE: RESISTOR, RSET, TOLERANCE WILL ADD
TO THE FREQUENCY ERROR
6905fd
1
1 page  
LTC6905
TYPICAL PERFORMANCE CHARACTERISTICS
ROUT vs V+
45
40
35
30
25
20
15
10
5
0
2.5 3 3.5 4 4.5
SUPPLY VOLTAGE (V)
5 5.5
6905 G04
Jitter vs Frequency
1.20
1.00
÷4 ÷2
0.80
÷1
0.60
0.40
0.20
0
0 20 40 60 80 100 120 140 160 180
FREQUENCY (MHz)
6905 G05
Frequency vs Temperature
1.0
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–40 –20 0 20 40 60 80 100 120
TEMPERATURE (°C)
6905 G08
LTC6905 Output Operating at
17.5MHz, VS = 3V
LTC6905 Output Operating at
170MHz, VS = 3V
1V/DIV
1V/DIV
12.5ns/DIV
6905 G06
1ns/DIV
6905 G07
PIN FUNCTIONS
V+ (Pin 1): Voltage Supply (2.7V ≤ V+ ≤ 5.5V). This sup-
ply must be kept free from noise and ripple. It should be
bypassed directly to the GND (Pin 2) with a 0.1μF capaci-
tor or higher.
GND (Pin 2): Ground. Should be tied to a ground plane
for best performance.
SET (Pin 3): Frequency-Setting Resistor Input. The value
of the resistor connected between this pin and V+ deter-
mines the oscillator frequency. The voltage on this pin is
held by the LTC6905 to approximately 1V below the V+
voltage. For best performance, use a precision metal film
resistor with a value between 10k and 25k and limit the
capacitance on this pin to less than 10pF.
DIV (Pin 4): Divider-Setting Input. This three-state input
selects among three divider settings, determining the value
of N in the frequency equation. Pin 4 should be tied to V+
for the ÷1 setting, the highest frequency range. Floating
Pin 4 divides the master oscillator by 2. Pin 4 should
be tied to GND for the ÷4 setting, the lowest frequency
range. To detect a floating DIV pin, the LTC6905 attempts
to pull the pin toward midsupply. This is realized with two
internal current sources, one tied to V+ and Pin 4 and the
other one tied to ground and Pin 4. Therefore, driving
the DIV pin high requires sourcing approximately 15μA.
Likewise, driving DIV low requires sinking 11μA. When
Pin 4 is floated, it should be bypassed by a 1nF capacitor
to ground or it should be surrounded by a ground shield
to prevent excessive coupling from other PCB traces.
OUT (Pin 5): Oscillator Output. This pin can drive 5kΩ
and/or 5pF loads. For larger loads, refer to the Applications
Information section.
6905fd
5
5 Page 
PACKAGE DESCRIPTION
S5 Package
5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
0.62 0.95
MAX REF
1.22 REF
2.90 BSC
(NOTE 4)
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 – 1.75
(NOTE 4)
LTC6905
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.20 BSC
DATUM ‘A’
0.30 – 0.50 REF
0.09 – 0.20
NOTE:
(NOTE 3)
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
PIN ONE
0.95 BSC
0.80 – 0.90
1.00 MAX
1.90 BSC
0.30 – 0.45 TYP
5 PLCS (NOTE 3)
0.01 – 0.10
S5 TSOT-23 0302
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
6905fd
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11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC6905.PDF ] | |
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