LTC6900IS5#TRPBF Linear Technology, LTC6900IS5#TRPBF Datasheet - Page 10

• Manufacturer Part Number: LTC6900IS5#TRPBF
• Description: IC OSC PREC LP RES SET TSOT23-5
• Manufacturer: Linear Technology
• Type: Oscillator, Siliconr

Specifications of LTC6900IS5#TRPBF

• Frequency: 20MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Current - Supply: 920µA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: TSOT-23-5, TSOT-5, TSOP-5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Count: -

LTC6900
APPLICATIONS INFORMATION
Once R
Example 1:
In this example, the oscillator output frequency has small
excursions. This is useful where the frequency of a system
should be tuned around some nominal value.
Let V
f
Equation (2), yielding R
Equation (4). R
tor values, use R
Figure 10 shows the measured f
to 2MHz frequency excursion is quite limited, so the curve
of f
10
OSC(MIN)
R
⎡
⎢
⎢
⎢
⎢
⎢
⎣
OSC
(
SET
V
+
IN(MAX)
IN
vs V
= 3V, f
Figure 10. Output Frequency vs Input Voltage
=
/R
2.00
1.95
1.90
1.85
1.80
1.75
1.70
1.65
1.60
1.55
1.50
= 1.5MHz for V
10MHz
SET
IN
0
N
is linear.
R
R
V
N = 1
− V
OSC(MAX)
IN
is known, calculate R
+
IN
SET
V
= 3V
RES
= 1.1M
= 9.9R
SET
0.5
= 110k
+
•
)
f
⎛
⎝ ⎜
OSC(MAX)
+ V
= 110k (1%) and R
R
R
1
20k
IN
SET
SET
RES
= 2MHz for V
IN
/R
IN
V
IN
= 1.089M. For standard resis-
1.5
SET
⎞
⎠ ⎟
⎛
⎝ ⎜
= 0V. Solve for R
(V)
1+
•
= 9.9/1. R
OSC
2
R
R
SET
IN
SET
vs V
2.5
⎞
⎠ ⎟
IN(MAX)
6900 F10
⎤
⎥
⎥
⎥
⎥
⎥
⎦
from:
IN
SET
IN
3
= 1.1M (1%).
. The 1.5MHz
= 110.1k by
IN
= 3V and
/R
SET
(3)
by
Example 2:
Vary the oscillator frequency by one octave per volt. As-
sume f
input voltage varies by 1V. The minimum input voltage is
half supply, that is V
V
Equation (2) yields R
R
resistor values, use R
(1%). Figure 11 shows the measured f
higher than 1.5V, the VCO is quite linear; nonlinearities
occur when V
VCO remains monotonic.
Maximum VCO Modulation Bandwidth
The maximum VCO modulation bandwidth is 25kHz; that
is, the LTC6900 will respond to changes in V
up to 25kHz. In lower frequency applications however, the
modulation frequency may need to be limited to a lower
rate to prevent an increase in output jitter. This lower limit
is the master oscillator frequency divided by 20, (f
In general, for minimum output jitter the modulation fre-
quency should be limited to f
is less. For best performance at all frequencies, the value
for f
when V
+
SET
= 3V.
OSC
= 142.8k. R
OSC(MIN)
IN
should be the master oscillator frequency (N = 1)
Figure 11. Output Frequency vs Input Voltage
3000
2500
2000
1500
1000
is at the lowest level.
500
0
0
IN
R
R
V
N = 1
+
IN
SET
= 1MHz and f
= 3V
becomes smaller than 1V, although the
= 182k
IN
0.5
= 143k
IN
= 1.273R
IN(MIN)
/R
SET
1
SET
V
= 143k (1%) and R
IN
= 1.273 and Equation (3) yields
1.5
= 1.5V, V
(V)
OSC
OSC(MAX)
SET
/20 or 25kHz, whichever
2
= 181.8k. For standard
2.5
IN(MAX)
OSC
= 2MHz, when the
6900 F11
vs V
3
= 2.5V and
IN
IN
IN
. For V
at a rate
OSC
= 182k
/20).
6900fa
IN