11
dc2048af
DEMO MANUAL DC2048A
connection to a Dust mote (Dc9003a-B)
Figure 14. Output Supercapacitor Discharging
When the Vibration Source Is Switched Off
Figure 13. Mide 25W Charging Output Supercapacitor
from 2.5V to 3.6V with Dust Mote Attached
While the EH_ON signal is low the buck-boost circuit
will consume 750nA from the battery in the sleeping
state. The effects of a pulsed load are shown in Figure 13
at approximately 1850s, where V
IN
is discharged and the
EH_ON signal pulses low to high for a brief period of time,
which occurred as a result of the Dust mote radio making
a data transmission.
Figure 14 shows the discharging of V
OUT
when the vibration
source is removed and V
IN
drops below the UVLO_FALLING
threshold causing EH_ON to go low. The supercapacitor
on V
OUT
will discharge down to the new target voltage of
2.5V at which point the buck-boost regulator will turn on
supplying power to the Dust mote. The discharging of
the supercapacitor on V
OUT
provides an energy source
for short term loss of the vibration source and extends
the life of the battery.
Figure 15 is the same Dust mote configuration as Figure 12
but without the output supercapacitor. Figure 16 shows the
charging of the output without the supercapacitor attached.
200s/DIV
DC2048A F13
EH_ON
5V/DIV
POVOUT
5V/DIV
V
OUT
1V/DIV
V
IN
200V/DIV
200s/DIV
DC2048A F14
EH_ON
5V/DIV
POVOUT
5V/DIV
V
OUT
1V/DIV
V
IN
200V/DIV
