Datasheet LT3690 (Analog Devices) - 9
| Fabricante | Analog Devices |
| Descripción | 36V, 4A, 1.5MHz Synchronous Step-Down Switching Regulator with 70μA Quiescent Current |
| Páginas / Página | 30 / 9 — pin FuncTions SW (Pins 1-4, 23-26, Exposed Pad Pin 27):. UVLO (Pin 12):. … |
| Formato / tamaño de archivo | PDF / 1.2 Mb |
| Idioma del documento | Inglés |
pin FuncTions SW (Pins 1-4, 23-26, Exposed Pad Pin 27):. UVLO (Pin 12):. VIN (Pins 13, 14, 15):. SYNC (Pin 5):. EN (Pin 17):
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LT3690
pin FuncTions SW (Pins 1-4, 23-26, Exposed Pad Pin 27):
The SW pin and thermal shutdown, the SS pin pulls low if the output is the emitter output of the internal highside NPN power voltage is below the power good threshold to restart the switch (HS) and the drain output of the internal lowside output voltage with soft-start behavior. If driving this pin power N-channel switch (LS). Connect this pin to the from a digital output, use at least 10k in series. Leave this inductor and boost capacitor. This pin is driven up to the pin disconnected if unused. VIN voltage by the HS switch during the on-time of the
UVLO (Pin 12):
Tie a resistor divider between V PWM duty cycle. The inductor current drives the SW pin IN, UVLO, and GND to program an undervoltage lockout threshold. negative during the off-time. The on-resistance of the LS The UVLO pin has an accurate 1.25V threshold. Above the switch and the internal Schottky diode fixes the negative threshold, the part operates normally. Below the threshold, voltage. the part drops into a low quiescent current state. See the The exposed pad is connected internally with SW pins Undervoltage Lockout section in the Applications Informa- 1-4, 23-26 and should be soldered to a large copper area tion section for more details. to reduce thermal resistance.
VIN (Pins 13, 14, 15):
The VIN pin supplies current to
SYNC (Pin 5):
The SYNC pin is used to synchronize the the LT3690’s internal regulator and to the internal power internal oscillator to an external signal. It is directly logic switch. This pin must be locally bypassed. compatible and can be driven with any signal between
EN (Pin 17):
The EN input is used to put the LT3690 in 20% and 80% duty cycle. The synchronizing range is shutdown mode. Pull to GND to shut down the LT3690. from 170kHz to 1.5MHz. See the Synchronization section Tie to 1.5V or more for normal operation. in the Applications Information section for details. When not used for synchronization, the SYNC pin can be tied
PG (Pin 18):
The PG pin is the open collector output of to ground to select low ripple Burst Mode operation or an internal comparator. PG remains low until the FB pin is tied to the output voltage to select standard PWM mode. within 10% of the final regulation voltage. The PG output is valid when V
RT (Pin 7):
Oscillator Resistor Input. Connecting a resis- IN is above 3.9V, the UVLO pin is high and EN is high. tor to ground (Pin 10) from this pin sets the switching frequency.
BIAS (Pin 19):
This pin connects to the anode of the internal boost Schottky diode. BIAS also supplies the current to
VC (Pin 8):
The VC pin is the output of the internal error the LT3690’s internal regulator. Tie this pin to the lowest amplifier. The voltage on this pin controls the peak switch available voltage source above 3V (typically V current. Tie an RC network from this pin to ground to OUT). This pin must be locally bypassed with 10nF. compensate the control loop.
V FB (Pin 9):
The LT3690 regulates the FB pin to 0.8V.
CCINT (Pin 20):
VCCINT is an output of the internally gen- erated supply voltage for the synchronous power DMOS Connect the feedback resistor divider tap to this pin. The transistor driver. An external capacitor C adjacent ground pin (Pin 10) is recommended for the VCC must be con- resistor divider. nected between this pin and ground (Pin 21) to buffer the internal supply voltage of the LS switch.
SS (Pin 11):
The SS pin is used to provide a soft-start or tracking function. The internal 2µA pull-up current
BST (Pin 22):
This pin is used to provide, with the external I boost capacitor, a drive voltage higher than the input volt- SS in combination with an external capacitor tied to this pin creates a voltage ramp. The output voltage tracks to age VIN to the internal bipolar NPN power switch. this voltage. For tracking, tie a resistor divider to this pin
GND (Exposed Pad Pin 28, Pin 6, Pin 10, Pin 16, Pin 21):
from the tracked output. In undervoltage, overvoltage Ground. The exposed pad is connected internally to GND Pins 6, 10, 16 and 21, and should be soldered to a large copper area to reduce thermal resistance. 3690fb For more information www.linear.com/LT3690 9 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 Typical Application Related Parts
pin FuncTions SW (Pins 1-4, 23-26, Exposed Pad Pin 27):
The SW pin and thermal shutdown, the SS pin pulls low if the output is the emitter output of the internal highside NPN power voltage is below the power good threshold to restart the switch (HS) and the drain output of the internal lowside output voltage with soft-start behavior. If driving this pin power N-channel switch (LS). Connect this pin to the from a digital output, use at least 10k in series. Leave this inductor and boost capacitor. This pin is driven up to the pin disconnected if unused. VIN voltage by the HS switch during the on-time of the
UVLO (Pin 12):
Tie a resistor divider between V PWM duty cycle. The inductor current drives the SW pin IN, UVLO, and GND to program an undervoltage lockout threshold. negative during the off-time. The on-resistance of the LS The UVLO pin has an accurate 1.25V threshold. Above the switch and the internal Schottky diode fixes the negative threshold, the part operates normally. Below the threshold, voltage. the part drops into a low quiescent current state. See the The exposed pad is connected internally with SW pins Undervoltage Lockout section in the Applications Informa- 1-4, 23-26 and should be soldered to a large copper area tion section for more details. to reduce thermal resistance.
VIN (Pins 13, 14, 15):
The VIN pin supplies current to
SYNC (Pin 5):
The SYNC pin is used to synchronize the the LT3690’s internal regulator and to the internal power internal oscillator to an external signal. It is directly logic switch. This pin must be locally bypassed. compatible and can be driven with any signal between
EN (Pin 17):
The EN input is used to put the LT3690 in 20% and 80% duty cycle. The synchronizing range is shutdown mode. Pull to GND to shut down the LT3690. from 170kHz to 1.5MHz. See the Synchronization section Tie to 1.5V or more for normal operation. in the Applications Information section for details. When not used for synchronization, the SYNC pin can be tied
PG (Pin 18):
The PG pin is the open collector output of to ground to select low ripple Burst Mode operation or an internal comparator. PG remains low until the FB pin is tied to the output voltage to select standard PWM mode. within 10% of the final regulation voltage. The PG output is valid when V
RT (Pin 7):
Oscillator Resistor Input. Connecting a resis- IN is above 3.9V, the UVLO pin is high and EN is high. tor to ground (Pin 10) from this pin sets the switching frequency.
BIAS (Pin 19):
This pin connects to the anode of the internal boost Schottky diode. BIAS also supplies the current to
VC (Pin 8):
The VC pin is the output of the internal error the LT3690’s internal regulator. Tie this pin to the lowest amplifier. The voltage on this pin controls the peak switch available voltage source above 3V (typically V current. Tie an RC network from this pin to ground to OUT). This pin must be locally bypassed with 10nF. compensate the control loop.
V FB (Pin 9):
The LT3690 regulates the FB pin to 0.8V.
CCINT (Pin 20):
VCCINT is an output of the internally gen- erated supply voltage for the synchronous power DMOS Connect the feedback resistor divider tap to this pin. The transistor driver. An external capacitor C adjacent ground pin (Pin 10) is recommended for the VCC must be con- resistor divider. nected between this pin and ground (Pin 21) to buffer the internal supply voltage of the LS switch.
SS (Pin 11):
The SS pin is used to provide a soft-start or tracking function. The internal 2µA pull-up current
BST (Pin 22):
This pin is used to provide, with the external I boost capacitor, a drive voltage higher than the input volt- SS in combination with an external capacitor tied to this pin creates a voltage ramp. The output voltage tracks to age VIN to the internal bipolar NPN power switch. this voltage. For tracking, tie a resistor divider to this pin
GND (Exposed Pad Pin 28, Pin 6, Pin 10, Pin 16, Pin 21):
from the tracked output. In undervoltage, overvoltage Ground. The exposed pad is connected internally to GND Pins 6, 10, 16 and 21, and should be soldered to a large copper area to reduce thermal resistance. 3690fb For more information www.linear.com/LT3690 9 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 Typical Application Related Parts