LTC3331_15 Datasheet, PDF (14/34 Pages) Linear Technology – Nanopower Buck-Boost DC/DC with Energy Harvesting Battery Charger

LTC3331
PIN FUNCTIONS
AC1 (Pin 8): Input Connection for piezoelectric element,
other AC source, or current limited DC source (used in
conjunction with AC2 for differential AC inputs).
AC2 (Pin 9): Input Connection for piezoelectric element,
other AC source, or current limited DC source (used in
conjunction with AC1 for differential AC inputs).
V_IN (Pin 10): Rectified Input Voltage. A capacitor on this
pin serves as an energy reservoir and input supply for the
buck regulator. The V_IN voltage is internally clamped to a
maximum of 20V (typical).
CAP (Pin 11): Internal Rail Referenced to V_IN to Serve
as Gate Drive for Buck PMOS Switch. Connect a 1μF (or
larger) capacitor between CAP and V_IN. This pin is not
intended for use as an external system rail.
SW (Pin 12): Switch Node for the Buck Switching Regula-
tor. Connect a 22µH or greater external inductor between
this node and V_OUT.
V_OUT (Pin 13): Regulated Output Voltage Derived from the
Buck or Buck-Boost Switching Regulator.
SWB (Pin 14): Switch Node for the Buck-Boost Switching
Regulator. Connect an external inductor (value in Table 3)
between this node and SWA.
SWA (Pin 15): Switch Node for the Buck-Boost Switching
Regulator. Connect an external inductor (value in Table 3)
between this node and SWB.
BB_IN (Pin 16): Input for the Buck-Boost Switching
Regulator. BB_IN must be tied to BAT_OUT for proper
operation.
IPK0, IPK1, IPK2 (Pins 17, 18, 19): I_{PEAK_BB} Select Bits
for the Buck-Boost Switching Regulator. Tie high to V_IN3
or low to GND to select the desired I_{PEAK_BB} (see Table 3).
Do not float.
BAT_OUT (Pin 20): This is the output side of the battery
disconnect switch. BAT_OUT must be connected to BB_IN
to power the buck-boost regulator.
BAT_IN (Pin 21): Input for backup battery and the input
side to the battery disconnect switch. When the battery
is disconnected there will be less than 10nA of quiescent
current draw at BAT_IN.
LBSEL (Pin 22): Low Battery Disconnect Select Pin.
Connect LBSEL high to BB_IN or low to GND to select
the low battery disconnect level. See Table 2. Do not float.
FLOAT1, FLOAT0 (Pins 23, 24): Float Voltage Select Pins.
Connect high to BB_IN or low to GND to select battery
float voltages of 3.45V, 4.0V, 4.1V, and 4.2V (see Table 2).
Do not float.
SHIP (Pin 25): Input to select SHIP mode. Tie SHIP to
at least 1.2V to select SHIP mode in which the battery
disconnect switch will be forced off, ensuring there is no
drain on the battery. Do not float.
V_IN3 (Pin 26): Internal Low Voltage Rail Used by the Pri-
oritizer. Logic high reference for IPK[2:0] and OUT[2:0].
Connect a 0.1µF capacitor from V_IN3 to GND. This pin is
not intended for use as an external system rail.
CHARGE (Pin 27): Connect a resistor from CHARGE to
the common BAT_OUT = BB_IN node to enable charging
of the battery. The CHARGE pin is controlled to provide
excess energy from the energy harvesting input when
the output is in regulation and the BUCK converter is in
SLEEP mode.
PGVOUT (Pin 28): Power Good Output for V_OUT. Logic
level output referenced to an internal maximum rail (see
Operation). PGVOUT transitioning high indicates regula-
tion has been reached on V_OUT (V_OUT = Sleep Rising).
PGVOUT remains high until V_OUT falls to 92% (typical)
of the programmed regulation point.
EH_ON (Pin 29): Switcher Status. Logic level output
referenced to V_IN3. EH_ON is high when the buck switching
regulator is in use (energy harvesting input). It is pulled
low when the buck-boost switching regulator is in use
(battery input).
OUT0, OUT1, OUT2 (Pins 30, 31, 32): V_OUT Voltage Select
Bits. Tie high to V_IN3 or low to GND to select the desired
V_OUT (see Table 1). Do not float.
GND (Exposed Pad Pin 33): Ground. The Exposed Pad
should be connected to a continuous ground plane on the
second layer of the printed circuit board by several vias
directly under the LTC3331.
14
For more information www.linear.com/LTC3331
3331fb