Datasheet LTC3109 (Analog Devices) - 6

LTC3109
Typical perForMance characTerisTics TA = 25°C, unless otherwise noted. LDO Step Load Response Enable Input and VOUT2 Running on Storage Capacitor
CSTORE = 470µF VOUT LOAD = 100µA CH3 V VSTORE LDO 20mV/DIV CH2 1V/DIV VOUT2 1V/DIV CH2, VOUT 1V/DIV CH4, VLDO ILDO CH1 1V/DIV 5mA/DIV VOUT2_EN CH1, VIN 1V/DIV 50mV/DIV 3109 G16 200µs/DIV 3109 G15 1ms/DIV 3109 G17 5SEC/DIV 0mA TO 3mA LOAD STEP 10mA LOAD ON VOUT2 CLDO = 2.2µF COUT = 220µF
pin FuncTions (QFN/SSOP) VSTORE (Pin 1/Pin 3):
Output for the Storage Capacitor or
PGOOD (Pin 6/Pin 8):
Power Good Output. When VOUT Battery. A large storage capacitor may be connected from is within 7.5% of its programmed value, this pin will be this pin to GND for powering the system in the event the pulled up to the LDO voltage through a 1M resistor. If input voltage is lost. It will be charged up to the maximum VOUT drops 9% below its programmed value PGOOD will VAUX clamp voltage. If not used, this pin should be left go low. This pin can sink up to 100µA. open or tied to VAUX.
VLDO (Pin 7/Pin 9):
Output of the 2.2V LDO. Connect a
VAUX (Pin 2/Pin 4):
Output of the Internal Rectifier Cir- 2.2µF or larger ceramic capacitor from this pin to GND. cuit and VCC for the IC. Bypass VAUX with at least 1µF of If not used, this pin should be tied to VAUX. capacitance to ground. An active shunt regulator clamps
GND (Pins 8, 11, 16, Exposed Pad Pin 21/Pins 10, 13,
VAUX to 5.25V (typical).
18):
Ground Pins. Connect these pins directly to the ground
VOUT (Pin 3/Pin 5):
Main Output of the Converter. The plane. The exposed pad serves as a ground connection and voltage at this pin is regulated to the voltage selected by as a means of conducting heat away from the die. VS1 and VS2 (see Table 1). Connect this pin to a reservoir
VS2 (Pin 20/Pin 2):
V capacitor or to a rechargeable battery. Any high current OUT Select Pin 2. Connect this pin to ground or VAUX to program the output voltage pulse loads must be fed by the reservoir capacitor on (see Table 1). this pin.
VS1 (Pin 19/Pin 1):
V
V
OUT Select Pin 1. Connect this
OUT2 (Pin 4/ Pin 6):
Switched Output of the Converter. pin to ground or VAUX to program the output voltage Connect this pin to a switched load. This output is open (see Table 1). until VOUT_EN is driven high, then it is connected to VOUT through a 1Ω PMOS switch. If not used, this pin should
Table 1. Regulated Output Voltage Using Pins VS1 and VS2
be left open or tied to VOUT .
VS2 VS1 VOUT V
GND GND 2.35V
OUT2_EN (Pin 5/Pin 7):
Enable Input for VOUT2. VOUT2 will be enabled when this pin is driven high. There is an GND VAUX 3.3V internal 5M pull-down resistor on this pin. If not used, VAUX GND 4.1V this pin can be left open or grounded. VAUX VAUX 5.0V 3109fb 6 For more information www.linear.com/LTC3109 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Typical Application Related Parts