LTC3108 Linear Technology, LTC3108 Datasheet - Page 6

• Manufacturer Part Number: LTC3108
• Description: Ultralow Voltage Step-Up Converter and Power Manager
• Manufacturer: Linear Technology

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LTC3108
PIN FUNCTIONS
VAUX (Pin 1/Pin 2): Output of the Internal Rectifi er Cir-
cuit and V
capacitance. An active shunt regulator clamps VAUX to
5.25V (typical).
VSTORE (Pin 2/Pin 3): Output for the Storage Capacitor
or Battery. A large capacitor may be connected from this
pin to GND for powering the system in the event the input
voltage is lost. It will be charged up to the maximum VAUX
clamp voltage. If not used, this pin should be left open
or tied to VAUX.
V
voltage at this pin is regulated to the voltage selected by
VS1 and VS2 (see Table 1). Connect this pin to an energy
storage capacitor or to a rechargeable battery.
V
Connect this pin to a switched load. This output is open
until V
V
pin should be left open or tied to V
in this output is limited to 0.3A typical.
VLDO (Pin 5/Pin 6): Output of the 2.2V LDO. Connect a
2.2μF or larger ceramic capacitor from this pin to GND.
If not used, this pin should be tied to VAUX.
PGD (Pin 6/Pin 7): Power Good Output. When V
within 7% of its programmed value, PGD will be pulled
up to VLDO through a 1MΩ resistor. If V
below its programmed value PGD will go low. This pin
can sink up to 100μA.
VS2 (Pin 7/Pin 10): V
to ground or VAUX to program the output voltage (see
Table 1).
6
OUT
OUT2
OUT
through a 1.3Ω P-channel switch. If not used, this
(Pin 3/Pin 4): Main Output of the Converter. The
(Pin 4/Pin 5): Switched Output of the Converter.
OUT2_EN
CC
for the IC. Bypass VAUX with at least 1μF of
is driven high, then it is connected to
OUT
Select Pin 2. Connect this pin
(DFN/SSOP)
OUT
. The peak current
OUT
drops 9%
OUT
is
VS1 (Pin 8/Pin 11): V
to ground or VAUX to program the output voltage (see
Table 1).
V
will be enabled when this pin is driven high. There is an
internal 5M pull-down resistor on this pin. If not used,
this pin can be left open or grounded.
C1 (Pin 10/Pin 13): Input to the Charge Pump and Rectifi er
Circuit. Connect a capacitor from this pin to the secondary
winding of the step-up transformer.
C2 (Pin 11/Pin 14): Input to the N-Channel Gate Drive
Circuit. Connect a capacitor from this pin to the secondary
winding of the step-up transformer.
SW (Pin 12/Pin 15): Drain of the Internal N-Channel
Switch. Connect this pin to the primary winding of the
transformer.
GND (Pins 1, 8, 9, 16) SSOP Only: Ground
Exposed Pad (Pin 13) DFN Only: Ground. The DFN Exposed
Pad must be soldered to the PCB ground plane. It serves
as the ground connection, and as a means of conducting
heat away from the die.
Table 1. Regulated Voltage Using Pins VS1 and VS2
OUT2_EN
VAUX
VAUX
GND
GND
VS2
(Pin 9/Pin 12): Enable Input for V
OUT
VAUX
VAUX
Select Pin 1. Connect this pin
GND
GND
VS1
OUT2
2.35V
V
3.3V
4.1V
5V
OUT
. V
OUT2
3108p