Datasheet LT3970 (Analog Devices) - 9

LT3970 Series
PIN FUNCTIONS FB (Pin 1, LT3970 Only):
The LT3970 Regulates the FB
GND (Pins 4, 5, Exposed Pad (Pin 11, DFN Only)):
Pin to 1.21V. Connect the feedback resistor divider tap Ground. Must be soldered to PCB. to this pin.
SW (Pin 6):
The SW pin is the output of an internal power
VOUT (Pin 1, LT3970-X Only):
The LT3970-3.3, LT3970- switch. Connect this pin to the inductor. 3.42 and LT3970-5 regulate the VOUT Pin to 3.3V, 3.42V
BOOST (Pin 7):
This pin is used to provide a drive voltage, and 5V respectively. This pin connects to the internal higher than the input voltage, to the internal bipolar NPN feedback divider that programs the fixed output voltage. power switch.
EN (Pin 2):
The part is in shutdown when this pin is low
BD (Pin 8):
This pin connects to the anode of the boost and active when this pin is high. The hysteretic thresh- diode. This pin also supplies current to the LT3970’s inter- old voltage is 1V going up and 0.97V going down. Tie to nal regulator when BD is above 3.2V. VIN if shutdown feature is not used. The EN threshold is accurate only when VIN is above 4.2V. If VIN is lower than
PG (Pin 9):
The PG pin is the open-drain output of an 4.2V, ground EN to place the part in shutdown. internal comparator. PG remains low until the FB pin is within 10% of the final regulation voltage. PG is valid
VIN (Pin 3):
The VIN pin supplies current to the LT3970’s when V internal circuitry and to the internal power switch. This IN is above 4.2V and EN is high. pin must be locally bypassed.
RT (Pin 10):
A resistor is tied between RT and ground to set the switching frequency. Rev. D For more information www.analog.com 9 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Related Parts