LTC3330_15 Datasheet, PDF (22/32 Pages) Linear Technology – Nanopower Buck-Boost DC/DC with Energy Harvesting Battery Life Extender

LTC3330
APPLICATIONS
Supercapacitor Balancer
If supercapacitors are used at V_OUT the onboard superca-
pacitor balancer can be used to balance them with ±10mA
of balance current. A list of supercapacitor suppliers is
provided in Table 6.
Table 6. Supercapacitor Suppliers
CAP-XX
www.cap-xx.com
NESS CAP
www.nesscap.com
Maxwell
www.maxwell.com
Bussman
www.cooperbussman.com
AVX
www.avx.com
Illinios Capacitor
www.illcap.com
Tecate Group
www.tecategroup.com
By seamlessly combining a battery source and an en-
ergy harvesting source, the LTC3330 enables the use of
supercapacitors in energy harvesting applications. The
battery provides the initial current required to overcome
the effects of the diffusion current when voltage is first
applied to the supercapacitors. The energy harvesting
source can then support the lower steady state leakage
current and average load current.
LDO Capacitors
The input to the low dropout regulator, LDO_IN, should
be bypassed with at least 4.7µF to GND. If LDO_IN is
connected to V_OUT the V_OUT capacitor may adequately
bypass the LDO input. If the board connection between
LDO_IN and V_OUT is long then an additional 1µF bypass
capacitor to GND near the LDO_IN pin may be required.
The LDO_OUT capacitor should be at least 22µF to keep
load step responses within 2% of regulation. A smaller
capacitor may lead to worse transient response and/or
instability whereas a higher capacitor will improve tran-
sient response.
CAP, V_IN2, and V_IN3 Capacitors
A 1μF or larger capacitor must be connected between V_IN
and CAP and a 4.7μF capacitor must be connected between
V_IN2 and GND. These capacitors hold up the internal rails
during buck switching and compensate the internal rail
generation circuits. In applications where the voltage at V_IN
is limited to less than 6V, the CAP pin can be tied to GND
and the V_IN2 pin can be tied to V_IN as shown in Figure 6.
An optional 5.6V Zener diode can be connected to V_IN
to clamp V_IN in this scenario. The leakage of the Zener
diode below its clamping voltage should be considered
as it could be comparable to the quiescent current of the
LTC3330. This circuit does not require the capacitors on
V_IN2 and CAP, saving two components and allowing for a
lower voltage rating for the single V_IN capacitor.
A 1µF or larger bypass capacitor must be connected from
V_IN3 to ground. V_IN3 is an internal rail that is shared by
both the buck and buck-boost. It is not intended for use as
a system rail. It is used as a the logic high reference level
for the IPK[2:0] and OUT[2:0] digital inputs. In the event
that these pins are dynamically driven in the application,
external inverters may be needed and they must use V_IN3
as a rail. However, care must be taken not to overload
V_IN3 and the quiescent current of such logic should be
kept minimal. The output resistance of the V_IN3 pin is
typically 15kΩ.
+
SOLAR
PANEL
–
AC2
AC1
V_IN
5.6V
22µF
(OPTIONAL)
6.3V
V_IN2
CAP
LTC3330
SW
V_OUT
SCAP
UV3
BAL
UV2
UVLOR = 4V
UVLOF = 3V
UV1
IPEAK_BB = 150mA
UV0
LDO_IN
LDO2
LDO1
+
Li-ION
33µH
4.7µF
6.3V
LDO0
BAT
LDO_EN
SWA
PGVOUT
PG_LDO
SWB
EH_ON
LDO_OUT
GND
V_IN3
IPK2 IPK1 IPK0 OUT2 OUT1 OUT0
+
SOLAR
PANEL
–
22µH
1.8V
22µF
6.3V
1µF
6.3V
3330 F06
Figure 6. Low Voltage Solar Harvester with Reduced
Component Count (V_IN < 6V)
3330fb
22
For more information www.linear.com/LTC3330