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LT3640IUFD Datasheet(PDF) 8 Page - Linear Technology |
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LT3640IUFD Datasheet(HTML) 8 Page - Linear Technology |
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8 / 24 page  LT3640 8 3640p PIN FUNCTIONS FB2 (Pin 1/Pin 26): The low voltage converter regulates the FB2 pin to 600mV. Connect the feedback resistor divider tap to this pin to set output voltage. PGOOD (Pin 2/Pin 27): Open-drain logic output that starts to sink current when FB2 is in regulation. EN/UVLO (Pin 3/Pin 28): Pull this pin below 0.3V to shut down the LT3640. The 1.26V threshold can function as an accurate undervoltage lockout, preventing the LT3640 from operating until VIN voltage has reached the programmed level. SYNC (Pin 4/Pin 1): Driving the SYNC pin with an external clock signal synchronizes both converters to the applied frequency. The lowest external clock frequency should be 20% higher than the internal oscillator frequency. SS1 (Pin 5/Pin 2): The SS1 pin sets the FB1 voltage ex- ternally between 0V and 1.265V, providing soft-start and tracking. Tie this pin 1.5V or higher to use the internal 1.265V reference. A capacitor to ground at this pin sets the ramp time to regulated output voltage for the high voltage converter. Use a resistor divider to track another supply. FB1 (Pin 6/Pin 3): The high voltage converter regulates the FB1 pin to 1.265V. Connect the feedback resistor divider tap to this pin to set output voltage. RT (Pin 7/Pin 4): Oscillator Resistor Input. Connecting a resistor to ground from this pin sets the internal oscillator frequency. RST2 (Pin 8/Pin 5): Open-drain logic output that remains asserted for the period set by the CPOR pin capacitor after FB2 goes above 550mV. RST1 (Pin 9/Pin 6): Open-drain logic output that remains asserted for the period set by the CPOR pin capacitor after FB1 goes above 1.165V. WDO (Pin 10/Pin 7): Open-drain logic output that remains asserted for the period set by the CPOR pin capacitor if WDE is enabled and WDI pin is not driven by an appropri- ate signal. CWDT (Pin 11/Pin 8): Connect a capacitor to ground at this pin to set watchdog timer. CPOR (Pin 12/Pin 9): Connect a capacitor to ground at this pin to set the power-on reset timer and WDO output timer. WDE (Pin 13/Pin 10): Watchdog Enable Pin. WDI (Pin 14/Pin 11): The WDI pin receives watchdog signals from a microprocessor. GND (Pins 15, 16, 23, 26, Exposed Pad 29/Pins 12, 13, 20, 23, Exposed Pad 29): Ground. These pins must be soldered to PCB ground. NC (Pin 17/Pin 14): Not Connected. DA (Pin 18/Pin 15): The DA pin is used to sense the catch diode current for current limit and protection. Connect this pin to catch diode anode. SW1 (Pin 19/Pin 16): Output of the High Voltage Internal Power Switch. Connect this pin to the inductor and catch diode cathode. SW (Pin 20/Pin 17): The SW pin is used to charge the boost capacitor. Connect this pin to the boost capacitor. BST (Pin 21/Pin 18): The BST pin is used to provide a drive voltage, higher than VIN pin voltage, to the high voltage channel internal power switch. Connect an external boost diode to this pin. VIN (Pin 22/Pin 19): The VIN pin supplies current to the LT3640’s internal circuitry and to the high voltage channel internal power switch. This pin must be locally bypassed. VIN2 (Pin 24/Pin 21): The VIN2 pin supplies current to the internal power MOSFET of the low voltage converter and to the LT3640’s internal circuitry when VIN2 is above 3V. SW2 (Pin 25/Pin 22): Switch Node of the Low Voltage Converter. Connect this pin to an inductor. EN2 (Pin 27/Pin 24): Low Voltage Converter Enable Pin. Pull this pin below 0.3V to shut down the low voltage converter. Pull this pin above 1.5V to enable the low volt- age converter. SS2 (Pin 28/Pin 25): The SS2 pin sets the FB2 voltage externally between 0V and 0.6V, providing soft-start and tracking. Tie this pin 0.8V or higher to use the internal 0.6V reference. A capacitor to ground at this pin sets the ramp time to regulated output voltage for the low voltage converter. Use a resistor divider to track another supply. (FE/QFN) |
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Similar Description - LT3640IUFD |
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