LTC6990 Linear Technology, LTC6990 Datasheet - Page 20

• Manufacturer Part Number: LTC6990
• Description: TimerBlox: Voltage Controlled Silicon Oscillator
• Manufacturer: Linear Technology

APPLICATIONS INFORMATION
LTC6990
Modulation Bandwidth and Settling Time
The LTC6990 will respond to changes in I
bandwidth of 0.4 • f
to stabilize a feedback loop around the LTC6990, since it
does not introduce a low-frequency pole.
Settling time depends on the master oscillator frequency.
Following a 2x or 0.5x step change in I
frequency takes approximately six master clock cycles
(6 • t
example is shown in Figure 16.
20
MASTER
Figure 15. Modulation Frequency Response
–10
–20
–30
–40
0
) to settle to within 1% of the fi nal value. An
0.1
R
R
DIVCODE = 4(÷16)
–3dB AT 0.4•f
SET
VCO
= 200k
= 464k
OUT
f
MOD
(see Figure 15). This makes it easy
OUT
/f
V
f
OUT
OUT
CTRL
1
(Hz/Hz)
=18.75kHz ±10%
= 0.536V + 0.278V
• SIN(2π•f
MOD
6990 F15
SET
•t)
SET
10
up to a –3dB
, the output
Power Supply Current
The power supply current varies with frequency, supply
voltage and output loading. It can be estimated under any
condition using the following equation:
The equation is also valid for OE = 0 (output disabled),
with f
I
+
S(TYP)
480kΩ
50kHz/DIV
V
2V/DIV
2V/DIV
OUT
V
+
CTRL
f
OUT
OUT
≈ V
= 0Hz.
+
V
R
f
OUT
+
+
SET
2 • R
= 3.3V, DIVCODE = 0
• f
= 175kHz AND 350kHz
= 200k, R
MASTER
V
LOAD
+
Figure 16. Settling Time
VCO
+ 1.75 •I
= 464k
• 7pF + V
10μs/DIV
SET
+
• f
+ 50µA
OUT
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• (13pF + C
6990 F16
LOAD
6990p
)