Datasheet LT3504 (Analog Devices) - 7
| Manufacturer | Analog Devices |
| Description | Quad 40V/1A Step-Down Switching Regulator with 100% Duty Cycle Operation |
| Pages / Page | 24 / 7 — pin FuncTions. DA (Pins 1, 3, 6, 8):. RT/SYNC (Pin 17):. SW (Pins 2, 4, … |
| File Format / Size | PDF / 498 Kb |
| Document Language | English |
pin FuncTions. DA (Pins 1, 3, 6, 8):. RT/SYNC (Pin 17):. SW (Pins 2, 4, 5, 7):. VIN (Pins 9, 11, 26, 28):
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Text Version of Document
LT3504
pin FuncTions DA (Pins 1, 3, 6, 8):
Return the Schottky catch diode
RT/SYNC (Pin 17):
Set the switching frequency of the anode to the diode anode (DA) pin. An internal compara- LT3504 by tying an external resistor from this pin to tor senses the diode current and prevents switching when ground. Select the value of the programming resistor the diode current is higher than the DA pin current limit. (RT) according to Table 1 in the Applications Information
SW (Pins 2, 4, 5, 7):
The SW pins are the output of the section. The RT/SYNC pin is also used to synchronize the internal power switches. Connect each SW pin to an in- internal oscillator of the LT3504 to an external signal. The ductor and Schottky catch diode cathode. synchronization (sync) signal is directly logical compatible and can be driven by any signal with pulse width greater
VIN (Pins 9, 11, 26, 28):
The VIN pins supply current to than 50ns. The synchronization range is from 250kHz to the LT3504’s internal regulator and to the internal power 2.2MHz. switches. The VIN pins should be tied together and locally bypassed with a capacitor to ground, preferably to pins
FB (Pins 19, 20, 21, 22):
Each feedback pin is regulated 10 and 27. to 800mV. Connect the feedback resistor divider to this pin. The output voltage is programmed according to the
GND (Pins 10, 18, 27, Exposed Pad Pin 29):
Tie the GND following equation: pins to a local ground plane below the LT3504 and the ⎛ V circuit components. The exposed pad must be soldered R1 ⎞ = R2 • OUT − 1 to the PCB and electrically connected to ground. Use a ⎝⎜ 0.8V ⎠⎟ large ground plane and thermal vias to optimize thermal where R1 connects between OUT and FB, and R2 connects performance. between FB and GND. A good value for R2 is 10kΩ.
RUN/SS (Pins 12, 13, 14, 15):
The RUN/SS pins are used
PG (Pin 23):
The Power Good pin is the open collector to soft start each channel and to allow each channel to output of an internal comparator. PG remains low until track other outputs. Output tracking is implemented by all FB pins are greater than 710mV. If not in use, this pin connecting a resistor divider to this pin from the tracked can be left unconnected. The PG comparator is disabled output. For soft start, tie a capacitor from this pin to ground. in shutdown. An internal 1.3µA soft-start current charges the capacitor to create a voltage ramp at the pin. Each channel can be
SW5 (Pin 24):
The SW5 pin is an open collector of an individually shut down by pulling RUN/SS below 0.1V. internal boost regulator power switch. This power switch generates the drive voltage 4.85V above the input voltage
EN/UVLO (Pin 16):
The EN/UVLO pin is used to start up (V the internal regulator to power the reference and oscilla- IN), to drive the internal buck regulator power switches. Connect an inductor from this pin to the V tor. It also starts up the internal boost regulator. Pull the IN pin. EN/UVLO pin below 1.44V to shut down the LT3504. The
SKY (Pin 25):
The SKY pin is the output of an integrated LT3504 will draw less than 10µA of current from the VIN power Schottky diode and is the source of drive voltage pin when EN/UVLO is less than 1.44V. Pull EN/UVLO pin to the internal buck regulator power switches. Connect a below 0.7V to put the LT3504 in a state where the part 1µF capacitor from this pin to the VIN pin. Do not drive this draws 0µA from the VIN pin. The threshold can function pin with an external voltage source. Do not draw current as an accurate undervoltage lockout (UVLO), preventing from this pin with an external component. the regulator from operating until the input voltage has reached the programmed level. Do not drive the EN/UVLO pin more than 5V above VIN. 3504fa For more information www.linear.com/LT3504 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 Package Description Revision History Typical Application Related Parts
pin FuncTions DA (Pins 1, 3, 6, 8):
Return the Schottky catch diode
RT/SYNC (Pin 17):
Set the switching frequency of the anode to the diode anode (DA) pin. An internal compara- LT3504 by tying an external resistor from this pin to tor senses the diode current and prevents switching when ground. Select the value of the programming resistor the diode current is higher than the DA pin current limit. (RT) according to Table 1 in the Applications Information
SW (Pins 2, 4, 5, 7):
The SW pins are the output of the section. The RT/SYNC pin is also used to synchronize the internal power switches. Connect each SW pin to an in- internal oscillator of the LT3504 to an external signal. The ductor and Schottky catch diode cathode. synchronization (sync) signal is directly logical compatible and can be driven by any signal with pulse width greater
VIN (Pins 9, 11, 26, 28):
The VIN pins supply current to than 50ns. The synchronization range is from 250kHz to the LT3504’s internal regulator and to the internal power 2.2MHz. switches. The VIN pins should be tied together and locally bypassed with a capacitor to ground, preferably to pins
FB (Pins 19, 20, 21, 22):
Each feedback pin is regulated 10 and 27. to 800mV. Connect the feedback resistor divider to this pin. The output voltage is programmed according to the
GND (Pins 10, 18, 27, Exposed Pad Pin 29):
Tie the GND following equation: pins to a local ground plane below the LT3504 and the ⎛ V circuit components. The exposed pad must be soldered R1 ⎞ = R2 • OUT − 1 to the PCB and electrically connected to ground. Use a ⎝⎜ 0.8V ⎠⎟ large ground plane and thermal vias to optimize thermal where R1 connects between OUT and FB, and R2 connects performance. between FB and GND. A good value for R2 is 10kΩ.
RUN/SS (Pins 12, 13, 14, 15):
The RUN/SS pins are used
PG (Pin 23):
The Power Good pin is the open collector to soft start each channel and to allow each channel to output of an internal comparator. PG remains low until track other outputs. Output tracking is implemented by all FB pins are greater than 710mV. If not in use, this pin connecting a resistor divider to this pin from the tracked can be left unconnected. The PG comparator is disabled output. For soft start, tie a capacitor from this pin to ground. in shutdown. An internal 1.3µA soft-start current charges the capacitor to create a voltage ramp at the pin. Each channel can be
SW5 (Pin 24):
The SW5 pin is an open collector of an individually shut down by pulling RUN/SS below 0.1V. internal boost regulator power switch. This power switch generates the drive voltage 4.85V above the input voltage
EN/UVLO (Pin 16):
The EN/UVLO pin is used to start up (V the internal regulator to power the reference and oscilla- IN), to drive the internal buck regulator power switches. Connect an inductor from this pin to the V tor. It also starts up the internal boost regulator. Pull the IN pin. EN/UVLO pin below 1.44V to shut down the LT3504. The
SKY (Pin 25):
The SKY pin is the output of an integrated LT3504 will draw less than 10µA of current from the VIN power Schottky diode and is the source of drive voltage pin when EN/UVLO is less than 1.44V. Pull EN/UVLO pin to the internal buck regulator power switches. Connect a below 0.7V to put the LT3504 in a state where the part 1µF capacitor from this pin to the VIN pin. Do not drive this draws 0µA from the VIN pin. The threshold can function pin with an external voltage source. Do not draw current as an accurate undervoltage lockout (UVLO), preventing from this pin with an external component. the regulator from operating until the input voltage has reached the programmed level. Do not drive the EN/UVLO pin more than 5V above VIN. 3504fa For more information www.linear.com/LT3504 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 Package Description Revision History Typical Application Related Parts
