LTC6905IS5 Linear Technology, LTC6905IS5 Datasheet - Page 10

• Manufacturer Part Number: LTC6905IS5
• Manufacturer: Linear Technology
• Type: Silicon Oscillatorr

Specifications of LTC6905IS5

• Mounting Style: Surface Mount
• Screening Level: Industrial
• Product Length (mm): 2.9mm
• Product Depth (mm): 1.75mm
• Product Height (mm): 0.9mm
• Package / Case: TSOT-23
• Lead Free Status / RoHS Status: Not Compliant

LTC6905
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. Since the voltage at the SET pin can
vary by as much as 5%, setting the frequency using a
current rather than a resistor will result in as much as 5%
additional inaccuracy in the output frequency.
APPLICATIONS INFORMATION
10
V
V
+
+
Figure 3. Current Controlled Oscillator
+
–
Figure 4. Voltage Controlled Oscillator
= 3V
R
10k
R
10k
R
33.2k
0.1μF
SET
I
0μA TO 60μA
CNTRL
SET
CNTRL
0.1μF
V
0V TO 2V
CNTRL
1
2
3
1
2
3
V
GND
SET
+
LTC6905
V
GND
SET
+
LTC6905
OUT
6905 F03
DIV
OUT
6905 F04
DIV
5
4
5
4
69.8MHz TO 170MHz
69.8MHz TO 170MHz
V
N = 1
V
N = 1
+
+
f
OSC
f
OSC
I
Example (Figure 3): V
V
Example (Figure 4): V
CNTRL
CNTRL
f
f
f
f
OSC
OSC
OSC
OSC
Frequency ≤ 100kHz
=
=
=
= [168.5MHz • (1 – 10kΩ • I
Frequency ≤ 100kHz
N
N
⎡
⎢
⎣
1
1
168 5
⎡
⎢
⎢
⎢
⎢
⎢
⎣
⎡
⎢
⎢
⎢
⎢
⎢
⎣
168 5
168 5
Figure 3 shows a method to control the frequency of the
LTC6905 using a current source. R
maximum frequency according to the regular expression
for f
SET pin to lower the frequency.
Figure 4 shows a method for controlling the frequency
of the LTC6905 using a voltage source. In this case, R
sets a constant current into the SET pin, and R
subtract from this current in order to change the frequency.
Increasing V
.
MHz
.
.
OSC
MHz
MHz
N = 1, V
. The current source will subtract current from the
•
SET
SET
10
•
•
10
10
k
Ω
= (V
= (V
CNTRL
k
k
V
Ω
Ω
•
+
+
⎡
⎢
⎣
•
+
•
+
10
= 3V
–
⎡
⎢
⎢
⎣
⎡
⎢
⎢
⎣
V
– 1V), R
– 1V), R
will increase the output frequency.
V
V
V
1
k
+
SET
Ω
+
+
–
R
R
–
–
SET
CNTRL
SET
–
V
SET
V
V
2
SET
SET
V V
SET
SET
33 2
–
) + 1.5MHz
–
–
.
= 10k, N = 1
= 10k, R
I
CNTRL
V
k
CNTRL
SET
Ω
SET
R
CNTRL
–
⎤ ⎤
⎥ +
⎦
⎤ ⎤
⎥
⎥
⎦
, in this case, sets a
V
+
CNTR
CNTRL
1 5 . MHz
. 1 5
MHz
L L
⎤
⎥
⎥
⎦
= 33.2k,
+
CNTRL
⎤
⎥
⎦
⎤
⎥
⎥
⎥
⎥
⎥
⎦
. 1 5
MHz
6905fd
will
SET
⎤
⎥
⎥
⎥
⎥
⎥ ⎥
⎦