
LTC6990
1
6990fc
For more information www.linear.com/LTC6990
TYPICAL APPLICATION
DESCRIPTION
TimerBlox: Voltage
Controlled Silicon Oscillator
The
LTC6990 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, RSET, programs the LTC6990’s internal
masteroscillatorfrequency.Theoutputfrequencyisdeter-
mined by this master oscillator and an internal frequency
divider,NDIV,programmabletoeightsettingsfrom1to128.
fOUT =
1MHz
NDIV
50k
RSET
, NDIV = 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.
Voltage Controlled Oscillator with 16:1 Frequency Range
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.
FEATURES
APPLICATIONS
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
72A Supply Current at 100kHz
n
500s 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
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
VCO Transfer Function
VCTRL (V)
0
f OUT
(kHz)
1000
750
250
500
0
0.5
6990 TA01b
2
1
1.5
6990 TA01a
LTC6990
OE
GND
SET
OUT
V+
DIV
C1
0.1F
RSET
100k
V+
VCTRL
RVCO
100k
fOUT = 1MHz VCTRL 0.5
MHz
V