Datasheet LT8620 (Analog Devices) - 8
| Manufacturer | Analog Devices |
| Description | 65V, 2A Synchronous Step-Down Regulator with 2.5μA Quiescent Current |
| Pages / Page | 26 / 8 — PIN FUNCTIONS SYNC:. SW:. BST:. TR/SS:. INTV. CC:. BIAS:. RT:. EN/UV:. … |
| File Format / Size | PDF / 599 Kb |
| Document Language | English |
PIN FUNCTIONS SYNC:. SW:. BST:. TR/SS:. INTV. CC:. BIAS:. RT:. EN/UV:. PG:. VIN:. FB:. GND:. NC:
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Text Version of Document
LT8620
PIN FUNCTIONS SYNC:
External Clock Synchronization Input. Ground this
SW:
The SW pins are the outputs of the internal power pin for low ripple Burst Mode operation at low output loads. switches. Tie these pins together and connect them to the Tie to a clock source for synchronization to an external inductor and boost capacitor. This node should be kept frequency. Apply a DC voltage of 3V or higher or tie to small on the PCB for good performance. INTVCC for pulse-skipping mode. When in pulse-skipping
BST:
This pin is used to provide a drive voltage, higher mode, the IQ will increase to several hundred µA. Do not than the input voltage, to the topside power switch. Place float this pin. a 0.1µF boost capacitor as close as possible to the IC.
TR/SS:
Output Tracking and Soft-Start Pin. This pin allows
INTV
user control of output voltage ramp rate during start-up. A
CC:
Internal 3.4V Regulator Bypass Pin. The in- ternal power drivers and control circuits are powered TR/SS voltage below 0.97V forces the LT8620 to regulate from this voltage. INTV the FB pin to equal the TR/SS pin voltage. When TR/SS CC maximum output current is 20mA. Do not load the INTV is above 0.97V, the tracking function is disabled and the CC pin with external cir- cuitry. INTV internal reference resumes control of the error amplifier. CC current will be supplied from BIAS if V An internal 2μA pull-up current from INTV BIAS > 3.1V, otherwise current will be drawn from VIN. CC on this pin Voltage on INTV allows a capacitor to program output voltage slew rate. CC will vary between 2.8V and 3.4V when V This pin is pulled to ground with an internal 220Ω MOS- BIAS is between 3.0V and 3.6V. Decouple this pin to power ground with at least a 1μF low ESR ceramic capacitor FET during shutdown and fault conditions; use a series placed close to the IC. resistor if driving from a low impedance output. This pin may be left floating if the tracking function is not needed.
BIAS:
The internal regulator will draw current from BIAS instead of V
RT:
A resistor is tied between RT and ground to set the IN when BIAS is tied to a voltage higher than 3.1V. For output voltages of 3.3V to 25V, this pin should switching frequency. be tied to VOUT. If this pin is tied to a supply other than
EN/UV:
The LT8620 is shut down when this pin is low and VOUT use a 1µF local bypass capacitor on this pin. If no active when this pin is high. The hysteretic threshold volt- supply is available, tie to ground. age is 1.00V going up and 0.96V going down. Tie to VIN
PG:
The PG pin is the open-drain output of an internal if the shutdown feature is not used. An external resistor comparator. PG remains low until the FB pin is within divider from VIN can be used to program a VIN threshold ±9% of the final regulation voltage, and there are no fault below which the LT8620 will shut down. conditions. PG is valid when VIN is above 3.4V, regardless
VIN:
The VIN pins supply current to the LT8620 internal of EN/UV pin state. circuitry and to the internal topside power switch. These
FB:
The LT8620 regulates the FB pin to 0.970V. pins must be tied together and be locally bypassed. Be Connect the feedback resistor divider tap to this pin. Also, sure to place the positive terminal of the input capacitor connect a phase lead capacitor between FB and V as close as possible to the V OUT. IN pins, and the negative Typically, this capacitor is 4.7pF to 10pF. capacitor terminal as close as possible to the PGND pins.
GND:
Ground. The exposed pad must be connected to the
NC:
No Connect. This pin is not connected to internal negative terminal of the input capacitor and soldered to circuitry. the PCB in order to lower the thermal resistance. 8620fa 8 For more information www.linear.com/LT8620 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 Typical Application Related Parts
PIN FUNCTIONS SYNC:
External Clock Synchronization Input. Ground this
SW:
The SW pins are the outputs of the internal power pin for low ripple Burst Mode operation at low output loads. switches. Tie these pins together and connect them to the Tie to a clock source for synchronization to an external inductor and boost capacitor. This node should be kept frequency. Apply a DC voltage of 3V or higher or tie to small on the PCB for good performance. INTVCC for pulse-skipping mode. When in pulse-skipping
BST:
This pin is used to provide a drive voltage, higher mode, the IQ will increase to several hundred µA. Do not than the input voltage, to the topside power switch. Place float this pin. a 0.1µF boost capacitor as close as possible to the IC.
TR/SS:
Output Tracking and Soft-Start Pin. This pin allows
INTV
user control of output voltage ramp rate during start-up. A
CC:
Internal 3.4V Regulator Bypass Pin. The in- ternal power drivers and control circuits are powered TR/SS voltage below 0.97V forces the LT8620 to regulate from this voltage. INTV the FB pin to equal the TR/SS pin voltage. When TR/SS CC maximum output current is 20mA. Do not load the INTV is above 0.97V, the tracking function is disabled and the CC pin with external cir- cuitry. INTV internal reference resumes control of the error amplifier. CC current will be supplied from BIAS if V An internal 2μA pull-up current from INTV BIAS > 3.1V, otherwise current will be drawn from VIN. CC on this pin Voltage on INTV allows a capacitor to program output voltage slew rate. CC will vary between 2.8V and 3.4V when V This pin is pulled to ground with an internal 220Ω MOS- BIAS is between 3.0V and 3.6V. Decouple this pin to power ground with at least a 1μF low ESR ceramic capacitor FET during shutdown and fault conditions; use a series placed close to the IC. resistor if driving from a low impedance output. This pin may be left floating if the tracking function is not needed.
BIAS:
The internal regulator will draw current from BIAS instead of V
RT:
A resistor is tied between RT and ground to set the IN when BIAS is tied to a voltage higher than 3.1V. For output voltages of 3.3V to 25V, this pin should switching frequency. be tied to VOUT. If this pin is tied to a supply other than
EN/UV:
The LT8620 is shut down when this pin is low and VOUT use a 1µF local bypass capacitor on this pin. If no active when this pin is high. The hysteretic threshold volt- supply is available, tie to ground. age is 1.00V going up and 0.96V going down. Tie to VIN
PG:
The PG pin is the open-drain output of an internal if the shutdown feature is not used. An external resistor comparator. PG remains low until the FB pin is within divider from VIN can be used to program a VIN threshold ±9% of the final regulation voltage, and there are no fault below which the LT8620 will shut down. conditions. PG is valid when VIN is above 3.4V, regardless
VIN:
The VIN pins supply current to the LT8620 internal of EN/UV pin state. circuitry and to the internal topside power switch. These
FB:
The LT8620 regulates the FB pin to 0.970V. pins must be tied together and be locally bypassed. Be Connect the feedback resistor divider tap to this pin. Also, sure to place the positive terminal of the input capacitor connect a phase lead capacitor between FB and V as close as possible to the V OUT. IN pins, and the negative Typically, this capacitor is 4.7pF to 10pF. capacitor terminal as close as possible to the PGND pins.
GND:
Ground. The exposed pad must be connected to the
NC:
No Connect. This pin is not connected to internal negative terminal of the input capacitor and soldered to circuitry. the PCB in order to lower the thermal resistance. 8620fa 8 For more information www.linear.com/LT8620 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 Typical Application Related Parts
