Datasheet LT8610AX (Analog Devices) - 4
| Manufacturer | Analog Devices |
| Description | 42V, 3.5A Synchronous Step-Down Regulator with Operation to 175°C |
| Pages / Page | 6 / 4 — PIN FUNCTIONS SYNC (Pin 1):. SW (Pins 9, 10, 11):. BST (Pin 12):. TR/SS … |
| File Format / Size | PDF / 525 Kb |
| Document Language | English |
PIN FUNCTIONS SYNC (Pin 1):. SW (Pins 9, 10, 11):. BST (Pin 12):. TR/SS (Pin 2):. INTV. CC (Pin 13):. BIAS (Pin 14):. RT (Pin 3):
Model Line for this Datasheet
Text Version of Document
LT8610AX
PIN FUNCTIONS SYNC (Pin 1):
External Clock Synchronization Input.
SW (Pins 9, 10, 11):
The SW pins are the outputs of the Ground this pin for low ripple Burst Mode operation at low internal power switches. Tie these pins together and con- output loads. Tie to a clock source for synchronization to nect them to the inductor and boost capacitor. This node an external frequency. Apply a DC voltage of 3V or higher should be kept small on the PCB for good performance. or tie to INTVCC for pulse-skipping mode. When in pulse-
BST (Pin 12):
This pin is used to provide a drive voltage, skipping mode, the IQ will increase to several hundred µA. higher than the input voltage, to the topside power switch. Do not float this pin. Place a 0.1µF boost capacitor as close as possible to the IC.
TR/SS (Pin 2):
Output Tracking and Soft-Start Pin. This
INTV
pin allows user control of output voltage ramp rate during
CC (Pin 13):
Internal 3.4V Regulator Bypass Pin. The internal power drivers and control circuits are pow- start-up. A TR/SS voltage below 0.97V forces the LT8610AX ered from this voltage. INTV to regulate the FB pin to equal the TR/SS pin voltage. When CC maximum output cur- rent is 20mA. Do not load the INTV TR/SS is above 0.97V, the tracking function is disabled CC pin with external circuitry. INTV and the internal reference resumes control of the error CC current will be supplied from BIAS if V amplifier. An internal 2.2μA pull-up current from INTV BIAS > 3.1V, otherwise current will be drawn from VIN. CC on Voltage on INTV this pin allows a capacitor to program output voltage slew CC will vary between 2.8V and 3.4V when V rate. This pin is pulled to ground with an internal 230Ω BIAS is between 3.0V and 3.6V. Decouple this pin to power ground with at least a 1μF low ESR ceramic capacitor MOSFET 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 (Pin 14):
The internal regulator will draw current from BIAS instead of V
RT (Pin 3):
A resistor is tied between RT and ground to IN when BIAS is tied to a voltage higher than 3.1V. For output voltages of 3.3V and above this pin set the switching frequency. should be tied to VOUT. If this pin is tied to a supply other
EN/UV (Pin 4):
The LT8610AX is shut down when this than VOUT use a 1µF local bypass capacitor on this pin. pin is low and active when this pin is high. The hysteretic
PG (Pin 15):
The PG pin is the open-drain output of an threshold voltage is 1.00V going up and 0.96V going internal comparator. PG remains low until the FB pin is down. Tie to VIN if the shutdown feature is not used. An within ±9% of the final regulation voltage, and there are external resistor divider from VIN can be used to program no fault conditions. PG is valid when V a V IN is above 3.4V, IN threshold below which the LT8610AX will shut down. regardless of EN/UV pin state.
VIN (Pins 5, 6):
The VIN pins supply current to the LT8610AX
FB (Pin 16):
The LT8610AX regulates the FB pin to 0.970V. internal circuitry and to the internal topside power switch. Connect the feedback resistor divider tap to this pin. Also, These pins must be tied together and be locally bypassed. connect a phase lead capacitor between FB and V Be sure to place the positive terminal of the input capaci- OUT. Typically, this capacitor is 4.7pF to 10pF. tor as close as possible to the VIN pins, and the negative capacitor terminal as close as possible to the GND pins.
GND (Pin 8, Exposed Pad Pin 17):
Ground. These pins are the return path of the internal bottom-side switch and
NC (Pin 7):
No Connect. This pin is not connected to must be tied together. Place the negative terminal of the internal circuitry. input capacitor as close to the GND pin and exposed pad as possible. The exposed pad must be soldered to the PCB in order to lower the thermal resistance. 8610axf 4 For more information www.linear.com/LT8610AX Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Electrical Characteristics Pin Configuration Typical Performance Characteristics Pin Functions Related Parts
PIN FUNCTIONS SYNC (Pin 1):
External Clock Synchronization Input.
SW (Pins 9, 10, 11):
The SW pins are the outputs of the Ground this pin for low ripple Burst Mode operation at low internal power switches. Tie these pins together and con- output loads. Tie to a clock source for synchronization to nect them to the inductor and boost capacitor. This node an external frequency. Apply a DC voltage of 3V or higher should be kept small on the PCB for good performance. or tie to INTVCC for pulse-skipping mode. When in pulse-
BST (Pin 12):
This pin is used to provide a drive voltage, skipping mode, the IQ will increase to several hundred µA. higher than the input voltage, to the topside power switch. Do not float this pin. Place a 0.1µF boost capacitor as close as possible to the IC.
TR/SS (Pin 2):
Output Tracking and Soft-Start Pin. This
INTV
pin allows user control of output voltage ramp rate during
CC (Pin 13):
Internal 3.4V Regulator Bypass Pin. The internal power drivers and control circuits are pow- start-up. A TR/SS voltage below 0.97V forces the LT8610AX ered from this voltage. INTV to regulate the FB pin to equal the TR/SS pin voltage. When CC maximum output cur- rent is 20mA. Do not load the INTV TR/SS is above 0.97V, the tracking function is disabled CC pin with external circuitry. INTV and the internal reference resumes control of the error CC current will be supplied from BIAS if V amplifier. An internal 2.2μA pull-up current from INTV BIAS > 3.1V, otherwise current will be drawn from VIN. CC on Voltage on INTV this pin allows a capacitor to program output voltage slew CC will vary between 2.8V and 3.4V when V rate. This pin is pulled to ground with an internal 230Ω BIAS is between 3.0V and 3.6V. Decouple this pin to power ground with at least a 1μF low ESR ceramic capacitor MOSFET 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 (Pin 14):
The internal regulator will draw current from BIAS instead of V
RT (Pin 3):
A resistor is tied between RT and ground to IN when BIAS is tied to a voltage higher than 3.1V. For output voltages of 3.3V and above this pin set the switching frequency. should be tied to VOUT. If this pin is tied to a supply other
EN/UV (Pin 4):
The LT8610AX is shut down when this than VOUT use a 1µF local bypass capacitor on this pin. pin is low and active when this pin is high. The hysteretic
PG (Pin 15):
The PG pin is the open-drain output of an threshold voltage is 1.00V going up and 0.96V going internal comparator. PG remains low until the FB pin is down. Tie to VIN if the shutdown feature is not used. An within ±9% of the final regulation voltage, and there are external resistor divider from VIN can be used to program no fault conditions. PG is valid when V a V IN is above 3.4V, IN threshold below which the LT8610AX will shut down. regardless of EN/UV pin state.
VIN (Pins 5, 6):
The VIN pins supply current to the LT8610AX
FB (Pin 16):
The LT8610AX regulates the FB pin to 0.970V. internal circuitry and to the internal topside power switch. Connect the feedback resistor divider tap to this pin. Also, These pins must be tied together and be locally bypassed. connect a phase lead capacitor between FB and V Be sure to place the positive terminal of the input capaci- OUT. Typically, this capacitor is 4.7pF to 10pF. tor as close as possible to the VIN pins, and the negative capacitor terminal as close as possible to the GND pins.
GND (Pin 8, Exposed Pad Pin 17):
Ground. These pins are the return path of the internal bottom-side switch and
NC (Pin 7):
No Connect. This pin is not connected to must be tied together. Place the negative terminal of the internal circuitry. input capacitor as close to the GND pin and exposed pad as possible. The exposed pad must be soldered to the PCB in order to lower the thermal resistance. 8610axf 4 For more information www.linear.com/LT8610AX Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Electrical Characteristics Pin Configuration Typical Performance Characteristics Pin Functions Related Parts
