LTC6991HS6 データシートの表示（PDF） - Linear Technology

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LTC6991HS6

TimerBlox: Resettable, Low Frequency Oscillator

Linear Technology 

LTC6991

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

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

RSET resistor is used, the supply current will not be much

larger than 100µA, so a simple regulator circuit can be

constructed using a Zener diode.

3V TO 20V

RSUPPLY

4.99k

1N4733A

5.1V

tOUT

3570 SECONDS

V+

OUT

R1

0.1µF LTC6991

1M

DIV

GND

R2

681k

RSET

665k

SET

RST

VREG

VIN

VOUT

SWITCHING

REGULATOR

SHDN

RFILT

100k

CFILT

0.1µF

V+

SYSTEM

DONE

6991 F12

THE SYSTEM CAN EXTEND tON AS LONG AS NEEDED (UP TO 50% OF tOUT)

tON

tON

tON

VREG

DONE/RST

LTC6991 OUT

tOUT

tOUT

tOUT

Figure 12. Powering Up a System Once an Hour

6991f

15

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