LTC6990_15 Datasheet, PDF (1/30 Pages) Linear Technology – Voltage Controlled Silicon Oscillator

LTC6990
TimerBlox: Voltage
Controlled Silicon Oscillator
FEATURES
n _{Fixed-Frequency or Voltage-Controlled Operation}
– Fixed: Single Resistor Programs Frequency
with <1.5% Max Error
– VCO: Two Resistors Set VCO Center
Frequency and Tuning Range
n _{Frequency Range: 488Hz to 2MHz}
n _{2.25V to 5.5V Single Supply Operation}
n _{72µA Supply Current at 100kHz}
n _{500µs Start-Up Time}
n _{VCO Bandwidth >300kHz at 1MHz}
n _{CMOS Logic Output Sources/Sinks 20mA}
n _{50% Duty Cycle Square Wave Output}
n _{Output Enable (Selectable Low or Hi-Z When Disabled)}
n _{–55°C to 125°C Operating Temperature Range}
n _{Available in Low Profile (1mm) SOT-23 (ThinSOT™)}
and 2mm × 3mm DFN Package
APPLICATIONS
n _{Low Cost Precision Programmable Oscillator}
n _{Voltage-Controlled Oscillator}
n _{High Vibration, High Acceleration Environments}
n _{Replacement for Fixed Crystal and Ceramic Oscillators}
n _{Portable and Battery-Powered Equipment}
L, LT, LTC and LTM, Linear Technology, TimerBlox and the Linear logo are registered
trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks
are the property of their respective owners. Protected by U.S. Patents, including 6342817,
6614313.
DESCRIPTION
The LTC^®6990 is a precision silicon oscillator with a pro-
grammable frequency range of 488Hz to 2MHz. It can be
used as a fixed-frequency or voltage-controlled oscillator
(VCO). The LTC6990 is part of the TimerBlox^® family of
versatile silicon timing devices.
A single resistor, R_SET, programs the LTC6990’s internal
master oscillator frequency. The output frequency is deter-
mined by this master oscillator and an internal frequency
divider, N_DIV, programmable to eight settings from 1 to 128.
f_OUT
=
1MHz
N_DIV
•
50kΩ
R_SET
,
N_DIV
=
1,
2,
4
…128
Optionally, a second resistor at the SET input provides
linear voltage control of the output frequency and can be
used for frequency modulation. A narrow or wide VCO
tuning range can be configured by the appropriate selec-
tion of the two resistors.
The LTC6990 includes an enable function that is synchro-
nized with the master oscillator to ensure clean, glitch-free
output pulses. The disabled output can be configured to
be high impedance or forced low.
For easy configuration of the LTC6990, download the
TimerBlox Designer tool at www.linear.com/timerblox.
TYPICAL APPLICATION
Voltage Controlled Oscillator with 16:1 Frequency Range
V_CTRL
V⁺
f_OUT
= 1MHz − V_CTRL
•
0.5
MHz
V
R_VCO
100k
OE
OUT
LTC6990
GND
V⁺
SET
R_SET
100k
DIV
6990 TA01a
V⁺
C1
0.1µF
VCO Transfer Function
1000
750
500
250
0
0
0.5
1
1.5
2
V_CTRL (V)
6990 TA01b
For more information www.linear.com/LTC6990
6990fc
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