LTC6991_15 Datasheet, PDF (1/24 Pages) Linear Technology – Resettable, Low Frequency Oscillator

FEATURES
n _{Period Range: 1ms to 9.5 Hours}
n _{Configured with 1 to 3 Resistors}
n _{<1.5% Maximum Frequency Error}
n _{Output Reset Function}
n _{2.25V to 5.5V Single Supply Operation}
n _{55μA to 80μA Supply Current}
(2ms to 9.5hr Clock Period)
n _{500μs Start-Up Time}
n _{CMOS Output Driver Sources/Sinks 20mA}
n _{–55°C to 125°C Operating Temperature Range}
n _{Available in Low Profile (1mm) SOT-23 (ThinSOT}^™₎
and 2mm × 3mm DFN Packages
APPLICATIONS
n _{“Heartbeat” Timers}
n _{Watchdog Timers}
n _{Intervalometers}
n _{Periodic “Wake-Up” Call}
n _{High Vibration, High Acceleration Environments}
n _{Portable and Battery-Powered Equipment}
L, LT, LTC, 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.
LTC6991
TimerBlox: Resettable, Low
Frequency Oscillator
DESCRIPTION
The LTC^®6991 is a silicon oscillator with a programmable
period range of 1.024ms to 9.54 hours (29.1μHz to 977Hz),
specifically intended for long duration timing events. The
LTC6991 is part of the TimerBlox^® family of versatile silicon
timing devices.
A single resistor, R_SET, programs the LTC6991’s internal
master oscillator frequency. The output clock period
is determined by this master oscillator and an internal
frequency divider, N_DIV, programmable to eight settings
from 1 to 2²¹.
t_OUT
= ^{NDIV • RSET}
50kΩ
• 1.024ms, N_DIV
= 1,8,64,...,2²¹
In normal operation, the LTC6991 oscillates with a 50%
duty cycle. A reset function is provided to truncate the
pulse (reducing the duty cycle). The reset pin can also be
used to prevent the output from oscillating.
The RST and OUT pins can be configured for active-low
or active-high operation using a polarity function.
POL BIT
0
0
1
1
RST PIN
0
1
0
1
OUTPUT STATE
Oscillating
0 (reset)
1 (reset)
Oscillating
For easy configuration of the LTC6991, download the
TimerBlox Designer tool at www.linear.com/timerblox.
TYPICAL APPLICATION
Low Frequency Pulse Generator
R_PW
2.26k
C_PW
470pF
RST
OUT
LTC6991
GND
V⁺
R_SET
715k
SET
DIV
t_PULSE ≈ R_PW
t
$_PW ≈ 1μs
1μs PULSE WIDTH
OUT
60 SECONDS
5V
R1
0.1μF
1M
R2
392k
6991 TA01a
Clock Period Range over Eight Divider Settings
10Hr
1Hr
10Min
1Min
10Sec
1Sec
100ms
10ms
1ms
0
0.625
1.25
1.875
2.5
DIV PIN VOLTAGE, V_DIV (V) 6991 TA01b
6991fb
1