LTC3588-1 Datasheet, PDF (11/20 Pages) Linear Technology – Piezoelectric Energy Harvesting Power Supply

LTC3588-1
OPERATION
The D0/D1 inputs can be switched while in regulation as
shown in Figure 3. If V_OUT is programmed to a voltage with
a PGOOD falling threshold above the old V_OUT, PGOOD will
transition low until the new regulation point is reached.
When V_OUT is programmed to a lower voltage, PGOOD
will remain high through the transition.
5
C_OUT = 100μF, I_LOAD = 100mA
D1=D0=0
4
D1=D0=1
D1=D0=0
3
2
V_OUT
1
PGOOD = LOGIC1
0
0 2 4 6 8 10 12 14 16 18 20
TIME (ms)
35881 F03
Figure 3. PGOOD Operation During D0/D1 Transition
Energy Storage
Harvested energy can be stored on the input capacitor
or the output capacitor. The wide input range takes ad-
vantage of the fact that energy storage on a capacitor is
proportional to the square of the capacitor voltage. After
the output voltage is brought into regulation any excess
energy is stored on the input capacitor and its voltage
increases. When a load exists at the output the buck can
efficiently transfer energy stored at a high voltage to the
regulated output. While energy storage at the input utilizes
the high voltage at the input, the load current is limited
to what the buck converter can supply. If larger loads
need to be serviced the output capacitor can be sized to
support a larger current for some duration. For example,
a current burst could begin when PGOOD goes high and
would continuously deplete the output capacitor until
PGOOD went low.
35881f
11