LTC3109_15 Datasheet, PDF (6/24 Pages) Linear Technology – Auto-Polarity, Ultralow Voltage Step-Up Converter and Power Manager

LTC3109
Typical Performance Characteristics T_A = 25°C, unless otherwise noted.
LDO Step Load Response
Enable Input and V_OUT2
V_LDO
20mV/DIV
I_LDO
5mA/DIV
200µs/DIV
0mA TO 3mA LOAD STEP
C_LDO = 2.2µF
CH2
V_OUT2
1V/DIV
3109 G15
CH1
V_{OUT2_EN}
1V/DIV
1ms/DIV
10mA LOAD ON V_OUT2
C_OUT = 220µF
3109 G16
Running on Storage Capacitor
CH3
VSTORE
1V/DIV
C_STORE = 470µF
V_OUT LOAD = 100µA
CH2, V_OUT
1V/DIV
CH4, V_LDO
1V/DIV
CH1, V_IN
50mV/DIV
5SEC/DIV
3109 G17
Pin Functions (QFN/SSOP)
VSTORE (Pin 1/Pin 3): Output for the Storage Capacitor or
Battery. A large storage 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.
VAUX (Pin 2/Pin 4): Output of the Internal Rectifier Cir-
cuit and V_CC for the IC. Bypass VAUX with at least 1µF of
capacitance to ground. An active shunt regulator clamps
VAUX to 5.25V (typical).
V_OUT (Pin 3/Pin 5): Main Output of the Converter. The
voltage at this pin is regulated to the voltage selected by
VS1 and VS2 (see Table 1). Connect this pin to a reservoir
capacitor or to a rechargeable battery. Any high current
pulse loads must be fed by the reservoir capacitor on
this pin.
V_OUT2 (Pin 4/ Pin 6): Switched Output of the Converter.
Connect this pin to a switched load. This output is open
until V_{OUT_EN} is driven high, then it is connected to V_OUT
through a 1Ω PMOS switch. If not used, this pin should
be left open or tied to V_OUT .
V_{OUT2_EN} (Pin 5/Pin 7): Enable Input for V_OUT2. V_OUT2
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.
PGOOD (Pin 6/Pin 8): Power Good Output. When V_OUT
is within 7.5% of its programmed value, this pin will be
pulled up to the LDO voltage through a 1M resistor. If
V_OUT drops 9% below its programmed value PGOOD will
go low. This pin can sink up to 100µA.
VLDO (Pin 7/Pin 9): 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.
GND (Pins 8, 11, 16, Exposed Pad Pin 21/Pins 10, 13,
18): Ground Pins. Connect these pins directly to the ground
plane. The exposed pad serves as a ground connection and
as a means of conducting heat away from the die.
VS2 (Pin 20/Pin 2): V_OUT Select Pin 2. Connect this
pin to ground or VAUX to program the output voltage
(see Table 1).
VS1 (Pin 19/Pin 1): V_OUT Select Pin 1. Connect this
pin to ground or VAUX to program the output voltage
(see Table 1).
Table 1. Regulated Output Voltage Using Pins VS1 and VS2
VS2
VS1
V_OUT
GND
GND
2.35V
GND
VAUX
3.3V
VAUX
GND
4.1V
VAUX
VAUX
5.0V
3109fb
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