10
dc2048af
DEMO MANUAL DC2048A
connection to a Dust mote (Dc9003a-B)
Figure 12 shows the LTC3330 with an output superca-
pacitor, a Dust mote attached, a battery installed and EH_ON
connected to OUT2. In this configuration, when EH_ON
is low, V
OUT
will be set to 2.5V and when EH_ON is high,
V
OUT
will be set to 3.6V. The first marker in Figure 13 is
where the vibration source was activated; V
IN
then rises
above the VIN_UVLO_RISING threshold. EH_ON will then
go high causing V
OUT
to rise towards 3.6V (V
OUT
started
at 2.5V because the battery had charged it up initially).
At the same time EH_ON goes high, PGVOUT will go low,
since the new V
OUT
level of 3.6V has not been reached.
As the charge on V
IN
is being transferred to V
OUT
, V
IN
is
discharging and when V
IN
reaches its UVLO_FALLING
threshold, EH_ON will go low, causing the targeted V
OUT
to again be 2.5V. Given that the output capacitor is very
large and the average load is less than the input power
supplied by the Mide piezoelectric transducer, the output
voltage will increase to the higher set-point of 3.6V over
many cycles. During the transition from the BAT set-point
Figure 12. Dust Mote Setup with a Supercapacitor,
a Battery and EH_ON Connected to OUT2
of 2.5V to the energy harvester set-point of 3.6V, V
OUT
is
above the 2.5V PGVOUT threshold, hence, PGVOUT will
go high every time EH_ON goes low. This cycle will be
repeated until V
OUT
reaches the PGVOUT threshold for the
V
OUT
setting of 3.6V. When a pulse load is applied that is
greater than the energy supplied by the input capacitor,
VIN will drop below the VIN_UVLO_FALLING threshold,
EH_ON will go low and the buck-boost regulator will be
ready to support the load requirement from the battery,
but will not start to switch until the supercapacitor is
discharged to 2.5V. In this way, the circuit can store a
lot of harvested energy and use it for an extended period
of time before switching over to the battery energy. The
supercapacitor could be sized to accommodate known
repeated periods of time that the energy harvester source
will not be available, such as overnight when a vibrating
machine is turned off or in the case of a solar application,
when the lights are turned off or the sun goes down.
PIEZO
MIDE V25W
1µF
6V
4.7µF, 6V
GND
LTC3330
DC2048A F12
AC1
V
IN
CAP
V
IN2
BAT
IPK2
IPK1
IPK0
UV3
UV2
UV1
UV0
OUT2
AC2
SW
SWA
22µH
22µH
SWB
V
OUT
SCAP
BAL
OUT1
OUT0
EH_ON
PGVOUT
V
IN3
22µF
25V
22µF
6V
CR2032
+
1µF
6V
180mF
2.5V
180mF
2.5V
HZ202F
100µF
10V
EHORBAT
PGOOD
V
SUPPLY
V
OUT
= 3.6V FOR EH_ON = 1
V
OUT
= 2.5V FOR EH_ON = 0
T
X
GND
LINEAR TECHNOLOGY DC9003A-A/B
DUST MOTE FOR WIRELESS MESH NETWORKS
NC7SZ58P8X
(x2)
