Datasheet LT3686A (Analog Devices) - 7

LT3686A
pin Functions (DFN/MSE) VIN (Pin 1/2):
The VIN pin supplies current to the LT3686A’s
EN/UVLO (Pin 6/7):
The EN/UVLO pin is used to start internal regulator and to the internal power switch. This up the LT3686A. Pull the pin below 0.4V to shutdown the pin must be local y bypassed. LT3686A. The 1.28V threshold can function as an accurate
BD (Pin 2/3):
When the SYNC/MODE Pin is driven with undervoltage lockout (UVLO), preventing the regulator clock pulses or tied greater than 0.8V, the LT3686A will from operating until the input voltage has reached the prevent pulse-skipping at light loads by regulating an programmed level. Do not drive the EN/UVLO pin above VIN. active load on the BD pin; see Applications Information
SYNC/MODE (Pin 7/8):
The SYNC/MODE pin is used section Fixed Frequency at Light Load. to synchronize the internal oscil ator of the LT3686A to
FB (Pin 3/4):
The LT3686A regulates its feedback pin to an external signal. The SYNC signal can be driven by a 0.8V. Connect the feedback resistor divider tap to this pin. signal with pulse width of at least 200ns on and off time. Set the output voltage according to: The SYNC/MODE Pin also acts as mode select for the BD active load; when it is driven with pulses or tied above   0.8V, the LT3686A will prevent pulse skipping at light loads R1=R2 VOUT  – 1 by regulating an active load on the BD pin. To disable the  0.8V  active load, tie SYNC/MODE to below 0.4V. A good value for R2 is 10k.
BOOST (Pin 8/9):
The BOOST pin is used to provide a
SS (Pin 4/5):
Provides Soft-Start and Tracking. An internal drive voltage, higher than the input voltage, to the internal 2µA current source tied to a 2.5V reference supplies cur- bipolar NPN power switch. rent to this pin to charge an external capacitor to create a
DA (Pin 9/10):
Connect catch diode (D1) anode to this voltage ramp at the pin. Feedback voltage and switching pin. frequency both track SS voltage. Feedback voltage stops
SW (Pin 10/11, 12):
The SW pin is the output of the tracking at 0.8V. SS is reset under UVLO, OVLO and thermal internal power switch. Connect this pin to the inductor, shutdown conditions. Float the pin if soft-start feature is catch diode and boost capacitor. not being used.
GND (Exposed Pad Pin 11/Pin 1, Exposed Pad Pin 13): RT (Pin 5/6):
The RT pin is used to program the oscil ator The exposed pad GND pin is the only ground connection frequency. Select the value of RT resistor according to table for the device. The exposed pad should be soldered to a 1 in the applications section of the data sheet. large copper area to reduce thermal resistance. 3686afa 7 Document Outline Features Description Applications Typical Application 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 Typical Application Related Parts