Datasheet LT3686 (Analog Devices) - 7
| Manufacturer | Analog Devices |
| Description | 37V/1.2A Step-Down Regulator in 3mm × 3mm DFN |
| Pages / Page | 28 / 7 — pin Functions VIN (Pin 1):. EN/UVLO (Pin 6):. BD (Pin 2):. MODE (Pin 7):. … |
| File Format / Size | PDF / 527 Kb |
| Document Language | English |
pin Functions VIN (Pin 1):. EN/UVLO (Pin 6):. BD (Pin 2):. MODE (Pin 7):. FB (Pin 3):. BOOST (Pin 8):. DA (Pin 9):. SS (Pin 4):
Model Line for this Datasheet
Text Version of Document
LT3686
pin Functions VIN (Pin 1):
The VIN pin supplies current to the LT3686’s
EN/UVLO (Pin 6):
The EN/UVLO pin is used to start up the internal regulator and to the internal power switch. This LT3686. Pull the pin below 0.4V to shutdown the LT3686. The pin must be locally bypassed. 1.27V threshold can function as an accurate undervoltage
BD (Pin 2):
The BD pin is used to provide current to lockout (UVLO), preventing the regulator from operating the internal Boost Schottky diode. Tie this pin to output until the input voltage has reached the programmed level. whenever possible. When the MODE pin is greater than Do not drive the EN/UVLO pin above VIN. 0.8V, the LT3686 will prevent pulse-skipping at light
MODE (Pin 7):
The MODE pin acts as mode select for the loads by regulating an active load on the BD pin; see the BD active load; when it is tied high, the LT3686 will prevent Applications Information section Fixed Frequency at Light pulse skipping at light loads by regulating an active load on Load. the BD pin. To disable the active load, tie MODE to GND.
FB (Pin 3):
The LT3686 regulates its feedback pin to 0.8V.
BOOST (Pin 8):
The BOOST pin is used to provide a drive Connect the feedback resistor divider tap to this pin. Set voltage, higher than the input voltage, to the internal bipolar the output voltage according to VOUT = 0.8(1 + R1/R2). A NPN power switch. good value for R2 is 10k.
DA (Pin 9):
Connect catch diode (D1) anode to this pin.
SS (Pin 4):
Provides Soft-Start and Tracking. An internal
SW (Pin 10):
The SW pin is the output of the internal power 2µA current source tied to a 2.5V reference supplies cur- switch. Connect this pin to the inductor, catch diode and rent to this pin to charge an external capacitor to create a boost capacitor. voltage ramp at the pin. Feedback voltage and switching frequency both track SS voltage. Feedback voltage stops
GND (Exposed Pad Pin 11):
The exposed pad GND pin is tracking at 0.8V. SS is reset under all fault conditions. Float the only ground connection for the device. The exposed the pin if soft-start feature is not being used. pad should be soldered to a large copper area to reduce thermal resistance.
RT (Pin 5):
The RT pin is used to program the oscillator frequency. Select the value of RT resistor according to Table 1 in the applications section of the data sheet. 3686fc 7 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 Typical Applications Package Description Revision History Related Parts
pin Functions VIN (Pin 1):
The VIN pin supplies current to the LT3686’s
EN/UVLO (Pin 6):
The EN/UVLO pin is used to start up the internal regulator and to the internal power switch. This LT3686. Pull the pin below 0.4V to shutdown the LT3686. The pin must be locally bypassed. 1.27V threshold can function as an accurate undervoltage
BD (Pin 2):
The BD pin is used to provide current to lockout (UVLO), preventing the regulator from operating the internal Boost Schottky diode. Tie this pin to output until the input voltage has reached the programmed level. whenever possible. When the MODE pin is greater than Do not drive the EN/UVLO pin above VIN. 0.8V, the LT3686 will prevent pulse-skipping at light
MODE (Pin 7):
The MODE pin acts as mode select for the loads by regulating an active load on the BD pin; see the BD active load; when it is tied high, the LT3686 will prevent Applications Information section Fixed Frequency at Light pulse skipping at light loads by regulating an active load on Load. the BD pin. To disable the active load, tie MODE to GND.
FB (Pin 3):
The LT3686 regulates its feedback pin to 0.8V.
BOOST (Pin 8):
The BOOST pin is used to provide a drive Connect the feedback resistor divider tap to this pin. Set voltage, higher than the input voltage, to the internal bipolar the output voltage according to VOUT = 0.8(1 + R1/R2). A NPN power switch. good value for R2 is 10k.
DA (Pin 9):
Connect catch diode (D1) anode to this pin.
SS (Pin 4):
Provides Soft-Start and Tracking. An internal
SW (Pin 10):
The SW pin is the output of the internal power 2µA current source tied to a 2.5V reference supplies cur- switch. Connect this pin to the inductor, catch diode and rent to this pin to charge an external capacitor to create a boost capacitor. voltage ramp at the pin. Feedback voltage and switching frequency both track SS voltage. Feedback voltage stops
GND (Exposed Pad Pin 11):
The exposed pad GND pin is tracking at 0.8V. SS is reset under all fault conditions. Float the only ground connection for the device. The exposed the pin if soft-start feature is not being used. pad should be soldered to a large copper area to reduce thermal resistance.
RT (Pin 5):
The RT pin is used to program the oscillator frequency. Select the value of RT resistor according to Table 1 in the applications section of the data sheet. 3686fc 7 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 Typical Applications Package Description Revision History Related Parts
