LTC6905CS5 [Linear]
17MHz to 170MHz Resistor Set SOT-23 Oscillator; 17MHz到170MHz的电阻设置SOT- 23振荡器
| 型号： | LTC6905CS5 |
| 厂家： | 
Linear |
| 描述： | 17MHz to 170MHz Resistor Set SOT-23 Oscillator |
| 文件： | 总8页 (文件大小：120K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC6905
17MHz to 170MHz
Resistor Set SOT-23 Oscillator
U
FEATURES
DESCRIPTIO
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.
■
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
(TA = 0°C to 70°C, Over All Settings)
±20ppm/°C Temperature Stability
Rise Time: 0.5ns, CL = 5pF
Timing Jitter: 50ps at 170MHz
50% ±2.5% Duty Cycle
6mA Typical Supply Current, fOSC = 100MHz
CMOS Output Drives 500Ω Load (VS = 3V)
Operates from a Single 2.7V to 5.5V Supply
Low Profile (1mm) ThinSOTTM Package
■
■
■
■
■
■
■
■
The LTC6905 operates with a single 2.7V to 5.5V power
supply and provides a rail-to-rail, 50% duty cycle square
waveoutput.TheCMOSoutputdriverensuresfastrise/fall
times and rail-to-rail switching. Operation is simple: A
singleresistor, RSET, between10Kto25Kisusedtosetthe
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.
U
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:
APPLICATIO S
■
High Frequency Precision Oscillator
■
High Speed Data Bus Clock
■
Fixed Crystal Oscillator Replacement
■
Ceramic Oscillator Replacement
1, DIV Pin = V+
⎧
⎪
⎛168.5MHz •10kΩ
⎞
1
⎠ N
, LTC and LT 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.
fOSC
=
+ 1.5MHz • , N = 2, DIV Pin = Open
⎜
⎟
⎨
⎝
RSET
⎪
4,DIV Pin = GND
⎩
For higher accuracy, fixed frequency versions that include
an internal frequency-setting resistor, see the LTC6905-
XXX Series datasheet.
U
Typical Distribution of Frequency Error, TA = 25°C
TYPICAL APPLICATIO
60
+
V
R
= 3V
= 12k
SET
DIV = 1
50
Basic Connection
40
30
17.225MHz ≤ f
≤ 170MHz
OSC
5V
1
2
3
5
+
V
OUT
LTC6905
0.1µF
5V
20
10
0
10k ≤ R
≤ 25k
SET
GND
SET
÷1
÷4
4
÷2
DIV
OPEN
6905 TA01
–0.5
–0.3
–0.1
0.1
0.3
0.5
6905 TA02
% ERROR
NOTE: RESISTOR, R , TOLERANCE WILL ADD
SET
TO THE FREQUENCY ERROR
6905fa
1
LTC6905
W W U W
U W
U
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(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
Specified Temperature Range (Note 8)
ORDER PART NUMBER
TOP VIEW
LTC6905CS5
LTC6905IS5
LTC6905HS5
+
V
1
5 OUT
4 DIV
GND 2
SET 3
S5 PART MARKING
LTBJC
S5 PACKAGE
5-LEAD PLASTIC SOT-23
TJMAX = 125°C, θJA = 150°C/W
LTC6905C ............................................... 0°C to 70°C
LTC6905I.............................................–40°C to 85°C
LTC6905H .........................................–40°C to 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ELECTRICAL CHARACTERISTICS
The ● 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 PARAMETER
∆f Frequency Accuracy (Notes 2, 9)
CONDITIONS
MIN
TYP
MAX
UNITS
+
V = 2.7V, 17.225MHz < f < 170MHz
±0.5
±1.4
±2.2
%
%
+
V = 5V, 17.225MHz < f < 170MHz
LTC6905CS5
+
V = 2.7V, 17.225MHz < f < 170MHz
●
●
±1.7
±2.5
%
%
+
V = 5V, 17.225MHz < f < 170MHz
LTC6905HS5 (25°C ≤ T ≤ 125°C),
LTC6905IS5 (25°C ≤ T ≤ 85°C)
+
V = 2.7V, 17.225MHz < f < 170MHz
±1.9
±2.9
%
%
+
V = 5V, 17.225MHz < f < 170MHz
LTC6905HS5 (–40°C ≤ T ≤ 125°C),
LTC6905IS5 (–40°C ≤ T ≤ 85°C)
+
V = 2.7V, 17.225MHz < f < 170MHz
●
●
±3.5
±3.5
%
%
+
V = 5V, 17.225MHz < f < 170MHz
R
Frequency-Setting Resistor Range
Maximum Frequency
10
25
kΩ
MHz
SET
MAX
MIN
+
f
f
Pin 4 = V , N = 1
170
17.225
±20
0.5
Minimum Frequency
Pin 4 = 0V, N = 4
MHz
∆f/∆T
∆f/∆V
Freq Drift Over Temp (Note 2)
Freq Drift Over Supply (Notes 2, 9)
Timing Jitter (Note 3)
R
SET
= 10k
●
●
ppm/°C
%/V
+
V = 2.7V to 5.5V, R = 10k
SET
0.8
%
Long-Term Stability of Output Frequency
Duty Cycle
300
50
ppm/√kHr
%-
●
●
47.5
2.7
52.5
5.5
+
V
Operating Supply Range
Power Supply Current
V
+
I
R
= 10k, N = 1, R = ∞,
V = 5.5V
●
●
14
7
20
12
mA
mA
S
SET
L
+
f
= 170MHz, C = 5pF
V = 2.7V
OSC
L
+
R
= 20k, N = 4, R = ∞,
V = 5.5V
●
●
5
3
7
5
mA
mA
SET
L
+
f
= 21.44MHz, C = 5pF
V = 2.7V
OSC
L
+
V
High Level DIV Input Voltage
●
V – 0.15
V
IH
6905fa
2
LTC6905
ELECTRICAL CHARACTERISTICS
otherwise noted. All voltages are with respect to GND.
The ● 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
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
0.2
UNITS
V
Low Level DIV Input Voltage
DIV Input Current (Note 4)
●
V
IL
+
+
I
Pin 4 = V
V = 5.5V
●
●
15
–11
40
µA
µA
DIV
+
Pin 4 = 0V
V = 5.5V
–40
+
V
High Level Output Voltage (Note 4)
Low Level Output Voltage (Note 4)
OUT Rise/Fall Time (Note 5)
V = 5.5V
I
I
= –1mA
= –4mA
●
●
5.25
5.20
5.45
5.30
V
V
OH
OL
OH
OH
+
V = 2.7V
I
I
= –1mA
= –4mA
●
●
2.5
2.4
2.6
2.4
V
V
OH
OH
+
V
V = 5.5V
I
I
= 1mA
= 4mA
●
●
0.05
0.2
0.25
0.3
V
V
OL
OL
+
V = 2.7V
I
I
= 1mA
= 4mA
●
●
0.1
0.4
0.3
0.5
V
V
OL
OL
t , t
r
0.5
ns
f
+
V
Voltage at R Pin
V = 5.5V
●
●
4.27
1.61
4.5
1.7
4.73
1.79
V
V
SET
SET
+
V = 2.7V
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 6: A heat sink may be required to keep the junction temperature
below the absolute maximum when the output is shorted indefinitely.
Note 2: Frequency accuracy is defined as the deviation from the f
equation. Accuracy is tested with DIV = V , N = 1 and other divide ratios
are guaranteed by design.
Note 3: Jitter is the ratio of the peak-to-peak distribution of the period to
the mean of the period. This specification is based on characterization and
is not 100% tested.
Note 7: The LTC6905C is guaranteed functional over the operating
temperature range.
Note 8: The LTC6905 is guaranteed to meet specified performance from
0°C to 70°C. The LTC6905C-XXX is designed, characterized and expected
to meet specified performance from –40°C to 85°C but is not tested or QA
sampled at these temperatures. The LTC6905I-XXX is guaranteed to meet
specified performance from –40°C to 85°C.
OSC
+
Note 4: To conform with the Logic IC Standard convention, current out of
a pin is arbitrarily given as a negative value.
Note 5: Output rise and fall times are measured between the 10% and
90% power supply levels.
Note 9: The LTC6905 is optimized for the performance with a 3V power
supply voltage. Please consult LTC Marketing for parts optimized for 5V
operation.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Frequency
Frequency Error vs RSET
Frequency Error vs Supply Voltage
0.60
0.40
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0
18
16
14
12
10
8
5.5V
2.7V
0.20
÷1
0
÷2
–0.20
–0.40
–0.60
–0.80
÷1
÷4
6
÷2
4
÷4
–0.20
2
0
–0.40
12
14
16
R
18
20
24
10
22
100
FREQUENCY (MHz)
0
50
150
200
2.5
3
3.5
4
5.5
4.5
5
(kΩ)
SUPPLY VOLTAGE (V)
SET
6905 G02
6905 G01
6905 G03
6905fa
3
LTC6905
U W
TYPICAL PERFOR A CE CHARACTERISTICS
ROUT vs V+
Jitter vs Frequency
Frequency vs Temperature
1.0
0.8
45
40
35
30
25
20
15
10
5
1.20
1.00
0.6
÷4
÷2
÷1
0.4
0.80
0.2
0
0.60
0.40
–0.2
–0.4
–0.6
–0.8
–1.0
0.20
0
0
–40 –20
0
20 40 60 80 100 120
2.5
3
3.5
4
5.5
4.5
5
0
20 40 60
100
140 160 180
120
80
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
FREQUENCY (MHz)
6905 G08
6905 G04
6905 G05
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
U
U
U
PI FU CTIO S
V+ (Pin 1): Voltage Supply (2.7V ≤ V+ ≤ 5.5V). This supply
must be kept free from noise and ripple. It should be
bypasseddirectlytotheGND(Pin2)witha0.1µFcapacitor
or higher.
of N in the frequency equation. Pin 4 should be tied to V+
forthe÷1setting,thehighestfrequencyrange.FloatingPin
4 divides the master oscillator by 2. Pin 4 should be tied to
GNDforthe÷4setting,thelowestfrequencyrange.Todetect
a floating DIV pin, the LTC6905 attempts to pull the pin
towardmidsupply.Thisisrealizedwithtwointernalcurrent
sources, one tied to V+ and Pin 4 and the other one tied to
ground and Pin 4. Therefore, driving the DIV pin high re-
quiressourcingapproximately15µA.Likewise,drivingDIV
low requires sinking 15µA. 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 cou-
pling from other PCB traces.
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.
OUT (Pin 5): Oscillator Output. This pin can drive 5kΩ
DIV (Pin 4): Divider-Setting Input. This three-state input
selectsamongthreedividersettings,determiningthevalue
and/or5pFloads.Forlargerloads,refertotheApplications
Information section.
6905fa
4
LTC6905
W
BLOCK DIAGRA
f
V
= 1V ±5%
MO
N
RES
f
=
+
+
OSC
PROGRAMMABLE
DIVIDER
(÷1, 2 OR 4)
(V – V
SET
)
V
OUT
1
5
+
R
SET
GAIN = 1
MASTER OSCILLATOR
I
RES
+
SET
DIVIDER
SELECT
V
3
2
–
15µA
–
+
DIV
THREE-STATE
INPUT DETECT
4
+
V
BIAS
–
I
RES
15µA
GND
GND
6905 BD
U
THEORY OF OPERATIO
As shown in the Block Diagram, the LTC6905’s master
oscillator is controlled by the ratio of the voltage between
the V+ and SET pins and the current entering the SET pin
(IRES). The voltage on the SET pin is forced to approxi-
mately 1V below V+ by the PMOS transistor and its gate
bias voltage.
master output frequency passed directly to OUT. The DIV
pin may be floated or driven to midsupply to select ÷2, the
intermediatefrequencyrange.Thelowestfrequencyrange,
÷4, is selected by tying DIV to GND or driving it below
0.5V. Figure 1 shows the relationship between RSET
,
divider setting and output frequency, including the over-
lapping frequencies.
A resistor RSET, connected between the V+ and SET pins,
“locks together” the voltage (V+ – VSET) and current, IRES
,
30
variation.ThisprovidestheLTC6905’shighprecision.The
master oscillation frequency reduces to:
25
÷4 ÷2
÷1
168.5MHz •10kΩ
20
15
10
5
fMO
=
+ 1.5MHz
RSET
To extend the output frequency range, the master oscilla-
tor signal is divided by 1, 2 or 4 before driving OUT (Pin
5). The LTC6905 is optimized for use with resistors
between 10k and 25k, corresponding to oscillator fre-
quencies between 17.225MHz and 170MHz. The divide-
by value is determined by the state of the DIV input
(Pin 4). Tie DIV to V+ or drive it to within 0.4V of V+ to
select ÷1. This is the highest frequency range, with the
110
160
10
60
OUTPUT FREQUENCY (MHz)
6905 F01
Figure 1. RSET vs Output Frequency
6905fa
5
LTC6905
W U U
U
APPLICATIO S I FOR ATIO
SELECTING THE DIVIDER SETTING AND RESISTOR
Example:AnLTC6905isoperatingwitha3Vpowersupply
and is set for a fOSC = 50MHz.
ROUT with V+ = 3V is 27Ω (using the ROUT vs V+ graph in
the Typical Performance Characteristics).
The LTC6905’s master oscillator has a frequency range
spanning 68.9MHz to 170MHz. A programmable divider
extendsthefrequencyrangefrom17.225MHzto170MHz.
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. Choosing a higher
divider setting will result in less jitter at the expense of
slightly higher supply current.
The maximum output CLOAD should be equal to or less
than [45454/(27 • 50)] = 33.6pF.
The lowest resistive load Pin 5 can drive can be calculated
using the minimum high level output voltage in the Elec-
trical Characteristics. With a V+ equal to 5.5V and 4mA
output current, the minimum high level output voltage is
5V and the lowest resistive load Pin 5 can drive is 1.25k
(5V/4mA). With a V+ equal to 2.7V and 4mA output
current,theminimumhighleveloutputvoltageis1.9Vand
thelowestresistiveloadPin5candriveis475Ω(1.9V/4mA).
Table 1. Frequency Range vs Divider Setting
DIVIDER SETTING
FREQUENCY RANGE
68.9MHz to 170MHz
34.45MHz to 85MHz
17.225MHz to 43MHz
+
÷1
÷2
÷4
⇒
⇒
⇒
DIV (Pin 4) = V
DIV (Pin 4) = Floating
DIV (Pin 4) = GND
After choosing the proper divider setting, determine the
correct frequency-setting resistor. Because of the linear
correspondence between oscillation period and resis-
tance,asimpleequationrelatesresistancewithfrequency.
FREQUENCY ACCURACY AND POWER SUPPLY NOISE
The frequency accuracy of the LTC6905 may be affected
when its power supply generates noise with frequency
contentsequaltofMO/64oritsmultiples(fMOistheinternal
LTC6905 master oscillator frequency before the divider
and fMO/64 is the master oscillator control loop fre-
quency). If for example, the master oscillator frequency is
set equal to 80MHz and the LTC6905 is powered by a
switching regulator, then the oscillator frequency may
show an additional error if the switching frequency is
1.4MHz (80MHz/64).
1
⎧
10k ⎛ 168.5MHz ⎞
N
⎪
RSET
=
•
, N = 2
⎨
⎟
⎜
⎝ fOSC – 1.5MHz⎠
(RSETMIN = 10k, RSETMAX = 25k)
Any resistor, RSET, tolerance adds to the inaccuracy of the
⎪4
⎩
oscillator, fOSC
.
START-UP TIME
JITTER AND POWER SUPPLY NOISE
Thestart-uptimeandsettlingtimetowithin1%ofthefinal
frequency is typically 100µs.
If the LTC6905 is powered by a supply that has frequency
contentsequaltotheoutputfrequencythentheoscillators
jitter may increase. In addition, power supply ripple in
excess of 20mV at any frequency may increase jitter.
MAXIMUM OUTPUT LOAD
The LTC6905 output (Pin 5) can drive a capacitive load
(CLOAD) of 5pF or more. Driving a CLOAD greater than 5pF
depends on the oscillator’s frequency (fOSC) and output
resistance (ROUT). The output rise time or fall time due to
ROUT and CLOAD is equal to 2.2 • ROUT • CLOAD (from 10%
to 90% of the rise or fall transition). If the total output rise
time plus fall time is arbitrarily specified to be equal to or
less than 20% of the oscillator’s period (1/fOSC), then the
maximumoutputCLOADinpicofarads(pF)shouldbeequal
to or less than [45454/(ROUT • fOSC)] (ROUT in ohms and
fOSC in MHz).
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 speci-
ficationtablesandJittervsFrequencygraphshowingjitter
at various divider ratios.
6905fa
6
LTC6905
W U U
APPLICATIO S I FOR ATIO
U
JITTER AND STRAY CAPACITANCE ON THE SET PIN
(PIN 3)
2) The resistor RSET should be placed as close as possible
to the LTC6905, and the connection of RSET to VCC
shouldbecloselysharedwiththebypasscapacitor.The
resistor RSET may be placed on the opposite side of the
board from the LTC6905, directly underneath the by-
pass capacitor.
The stray capacitance on the SET pin (Pin 3) should be
limited to 10pF or less to avoid increased jitter or unstable
oscillation.
3) Ifagroundplaneisused,theconnectionoftheLTC6905
tothegroundplaneshouldbeascloseaspossibletothe
LTC6905GNDpinandshouldbecomposedofmultiple,
high current capacity vias.
LTC6905 SUGGESTED CRITICAL COMPONENT
LAYOUT
In order to provide the specified performance, it is re-
quired that the frequency setting resistor RSET and the
supply bypass capacitor be placed as close as possible to
the LTC6905. The following additional rules should be
followed for best performance:
R
C
1) The bypass capacitor must be placed as close as
possible to the LTC6905, and no vias should be placed
between the capacitor and the LTC6905. The bypass
capacitor must be on the same side of the circuit board
as the LTC6905.
LTC6905
6905 F02
Figure 2. LTC6905 Suggested Critical Component Layout
U
S5 Package
PACKAGE DESCRIPTIO
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
1.50 – 1.75
(NOTE 4)
2.80 BSC
1.4 MIN
3.85 MAX 2.62 REF
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
DATUM ‘A’
0.01 – 0.10
1.00 MAX
0.30 – 0.50 REF
1.90 BSC
0.09 – 0.20
(NOTE 3)
NOTE:
S5 TSOT-23 0302
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
6905fa
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
7
LTC6905
W U U
U
APPLICATIO S I FOR ATIO
ALTERNATIVE METHODS OF SETTING THE OUTPUT
FREQUENCY OF THE LTC6905
Figure 3 shows a method to control the frequency of the
LTC6905 using a current source. RSET, in this case, sets a
maximum frequency according to the regular expression
for fOSC. The current source will subtract current from the
SET pin to lower the frequency.
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
theLTC6905takesintoaccountboththevoltageattheSET
pin and the current into the SET pin when generating the
outputfrequency. SincethevoltageattheSETpincanvary
by as much as 5%, setting the frequency using a current
rather than a resistor will result in as much as 5% addi-
tional inaccuracy in the output frequency.
Figure 4 shows a method for controlling the frequency of
theLTC6905usingavoltagesource.Inthiscase,RSET sets
a constant current into the SET pin, and RCNTRL will sub-
tract from this current in order to change the frequency.
Increasing VCNTRL will increase the output frequency.
+
⎡
⎢
⎢
⎢
⎢
⎤
⎥
⎥
⎥
⎥
⎡
⎢
⎣
⎤
⎥
⎦
V – VSET
RSET
168.5MHz •10kΩ •
–ICNTRL
+
1
N
V
fOSC
=
+ 1.5MHz
1
2
3
5
4
+
V+ – VSET
V
OUT
LTC6905
0.1µF
f
OSC
69.8MHz TO 170MHz
⎢
⎥
GND
SET
R
⎣
⎦
SET
10k
+
V
DIV
ICNTRL Frequency ≤ 100kHz
Example (Figure 3): VSET = (V+ – 1V), RSET = 10k, N = 1
N = 1
I
CNTRL
0µA TO 60µA
6905 F03
fOSC = 168.5MHz • 1– 10kΩ •I
+ 1.5MHz
(
)
[
]
CNTRL
Figure 3. Current Controlled Oscillator
+
⎡
⎢
⎢
⎢
⎢
⎤
⎥
⎥
⎥
⎥
⎡
⎢
⎣
⎤
⎥
⎦
V – VSET
RSET
VSET – VCNTRL
168.5MHz •10kΩ •
–
RCNTRL
1
N
fOSC
=
+ 1.5MHz
+
V
= 3V
0.1µF
V+ – VSET
1
2
3
5
4
+
V
OUT
⎢
⎥
LTC6905
f
⎣
⎦
OSC
69.8MHz TO 170MHz
GND
SET
R
SET
10k
VCNTRL Frequency ≤ 100kHz
Example (Figure 4): VSET = (V+ – 1V), RSET = 10k, RCNTRL = 33.2k,
+
V
DIV
N = 1
R
CNTRL
33.2k
6905 F04
N = 1, V+ = 3V
V
CNTRL
0V TO 2V
+
–
⎡
⎤
1
2V – VCNTRL
33.2kΩ
⎡
⎤
f
OSC = 168.5MHz •10kΩ •
–
+ 1.5MHz
⎢
⎥
⎢
⎥
10kΩ
Figure 4. Voltage Controlled Oscillator
⎣
⎦
⎣
⎦
RELATED PARTS
PART NUMBER
LTC1799
DESCRIPTION
COMMENTS
1kHz to 33MHz ThinSOT Oscillator
1kHz to 20MHz ThinSOT Oscillator
Single Output, High Frequency Operation
Single Output Lower Power
LTC6900
LTC6902
LTC6903/LTC6904
Multiphase Oscillator with Spread Spectrum Modulation
1kHz to 68MHz Serial Port Programmable Oscillator
2-, 3- or 4-Phase Outputs
3-Wire or I CTM Programmable
2
LTC6905-XXX Series Fixed Frequency LTC6905
High Accuracy, No External Resistor
LTC6906
Micropower, 10kHz to 1MHz Resistor Set ThinSOT Oscillator
Ultralow Power, Resistor Sets Frequency
2
I C is a trademark of Philips Electronics N.V.
6905fa
LT/TP 0205 1K REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
8
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2005
相关型号：
LTC6905CS5#TRM
LTC6905 - 17MHz to 170MHz Resistor Set SOT-23 Oscillator; Package: SOT; Pins: 5; Temperature Range: 0°C to 70°C
Linear
LTC6905CS5#TRMPBF
LTC6905 - 17MHz to 170MHz Resistor Set SOT-23 Oscillator; Package: SOT; Pins: 5; Temperature Range: 0°C to 70°C
Linear
LTC6905CS5-100#PBF
LTC6905-XXX - Fixed Frequency SOT-23 Oscillator; Package: SOT; Pins: 5; Temperature Range: 0°C to 70°C
Linear
LTC6905CS5-100#TRMPBF
LTC6905-XXX - Fixed Frequency SOT-23 Oscillator; Package: SOT; Pins: 5; Temperature Range: 0°C to 70°C
Linear
LTC6905CS5-133#TR
LTC6905-XXX - Fixed Frequency SOT-23 Oscillator; Package: SOT; Pins: 5; Temperature Range: 0°C to 70°C
Linear
LTC6905CS5-133#TRM
LTC6905-XXX - Fixed Frequency SOT-23 Oscillator; Package: SOT; Pins: 5; Temperature Range: 0°C to 70°C
Linear
©2020 ICPDF网 联系我们和版权申明