LTC3105
6
3105fb
For more information www.linear.com/LTC3105
PIN FUNCTIONS
FB (Pin 1/Pin 1): Step-Up Converter Feedback Input.
Connect the V
OUT
resistor divider tap to this input. The
output voltage can be adjusted between 1.6V and 5.25V.
LDO (Pin 2/Pin 2): LDO Regulator Output. Connect a 4.7µF
or larger capacitor between LDO and GND.
FBLDO (Pin 3/Pin 3): LDO Feedback Input. Connect the
LDO resistive divider tab to this input. Alternatively, con
-
necting FBLDO directly to GND will configure the LDO
output voltage to be internally set at 2.2V (nominal).
SHDN (Pin 4/Pin 4): Logic Controlled Shutdown Input.
With SHDN open, the converter is enabled by an internal
2MΩ pull-up resistor. The SHDN pin should be driven with
an open-drain or open-collector pull-down and floated until
the converter has entered normal operation. Excessive
loading on this pin may cause a failure to complete start-up.
SHDN = Low: IC Disabled
SHDN = High: IC Enabled
MPPC (Pin 5/Pin 5): Set Point Input for Maximum
Power Point Control. Connect a resistor from MPPC to
GND to program the activation point for the MPPC loop.
T
o disable the MPPC circuit, connect MPPC directly
to GND.
V
IN
(Pin 6/Pin 8): Input Supply. Connect a decoupling
capacitor between this pin and GND. The PCB trace length
from the V
IN
pin to the decoupling capacitor should be as
short and wide as possible. When used with high imped-
ance sources such as photovoltaic cells, this pin should
have a 10µF or larger decoupling capacitor
.
GND (Exposed Pad Pin 11/Pins 6, 7) :
Small Signal and
Power Ground for the IC. The GND connections should be
soldered to the PCB ground using the lowest impedance
path possible.
SW (Pin 7/Pin 9): Switch Pin. Connect an inductor between
SW and V
IN
. PCB trace lengths should be as short as pos-
sible to reduce EMI. While the converter is sleeping or is
in shutdown, the internal antiringing switch connects the
SW pin to the V
IN
pin in order to minimize EMI.
PGOOD (Pin 8/Pin 10): Power Good Indicator. This is an
open-drain output. The pull-down is disabled when V
OUT
has achieved the voltage defined by the feedback divider
on the FB pin. The pull-down is also disabled while the IC
is in shutdown or start-up mode.
V
OUT
(Pin 9/Pin 11): Step-Up Converter Output. This is the
drain connection of the main output internal synchronous
rectifier. A 10µF or larger capacitor must be connected
between this pin and GND. The PCB trace length from the
V
OUT
pin to the output filter capacitor should be as short
and wide as possible.
AUX (Pin 10/Pin 12): Auxiliary Voltage. Connect a 1µF
capacitor between this pin and GND. This pin is used by
the start-up circuitry to generate a voltage rail to power
internal circuitry until the main output reaches regulation.
AUX and V
OUT
are internally connected together once V
OUT
exceeds V
AUX
.
(DFN/MSOP)
