LTC6991 Linear Technology, LTC6991 Datasheet - Page 15

• Manufacturer Part Number: LTC6991
• Description: Resettable Low Frequency Oscillator
• Manufacturer: Linear Technology

DataSheet.in
applicaTions inForMaTion
LTC6991 as “Wake-Up Timer”
The output latch reset function provided by the RST pin
allows the LTC6991 to enable a larger system at regular
intervals. The on-time can be controlled by the system.
This allows the system to shut itself down immediately after
performing its tasks, reducing power consumption.
Figure 12 shows an example using “black boxes” for a
switching regulator and the system being duty-cycled.
In some cases, an RC filter may be necessary at the RST
LTC6991 OUT
DONE/RST
V
REG
3V TO 20V
R
4.99k
1N4733A
5.1V
SUPPLY
t
ON
Figure 12. Powering Up a System Once an Hour
THE SYSTEM CAN EXTEND t
R1
1M
R2
681k
t
OUT
R
665k
SET
0.1µF
V
DIV
SET
+
LTC6991
ON
t
ON
AS LONG AS NEEDED (UP TO 50% OF t
input to filter start-up glitches from the system as it is
powered on.
If the LTC6991 is enabling a switching regulator that can
operate on supplies greater than 5.5V, it will be necessary
to limit the supply voltage provided to the LTC6991. If
the LTC6991 output is not heavily loaded, and if a large
R
larger than 100µA, so a simple regulator circuit can be
constructed using a Zener diode.
t
OUT
GND
OUT
RST
SET
3570 SECONDS
resistor is used, the supply current will not be much
t
OUT
C
0.1µF
FILT
R
100k
V
SHDN
FILT
IN
REGULATOR
SWITCHING
t
ON
t
OUT
V
OUT
OUT
DONE
)
SYSTEM
V
REG
V
+
6991 F12
LTC6991

6991p