Datasheet LTC7800 (Analog Devices) - 9
| Hersteller | Analog Devices |
| Beschreibung | Low IQ , 60V, High Frequency Synchronous Step-Down Controller |
| Seiten / Seite | 32 / 9 — PIN FUNCTIONS. PGOOD (Pin 9):. PGND (Pin 16):. TG (Pin 10):. VIN (Pin … |
| Dateiformat / Größe | PDF / 1.3 Mb |
| Dokumentensprache | Englisch |
PIN FUNCTIONS. PGOOD (Pin 9):. PGND (Pin 16):. TG (Pin 10):. VIN (Pin 17):. LIM (Pin 18):. SW (Pin 11):. BOOST (Pin 12):
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LTC7800
PIN FUNCTIONS PGOOD (Pin 9):
Open-Drain Logic Output. PGOOD is pulled
PGND (Pin 16):
Driver Power Ground. Connects to the to ground when the voltage on the VFB pin is not within source of bottom (synchronous) N-channel MOSFET and 10% of its set point. the (–) terminal of CIN.
TG (Pin 10):
High Current Gate Drives for Top N-channel
VIN (Pin 17):
Main Supply Pin. A bypass capacitor should MOSFET. This is the output of floating driver with a volt- be tied between this pin and the SGND pins. age swing equal to INTVCC superimposed on the switch
I
node voltage SW.
LIM (Pin 18):
Current Comparator Sense Voltage Range Inputs. Tying this pin to SGND, FLOAT or INTVCC sets the
SW (Pin 11):
Switch Node Connection to Inductor. maximum current sense threshold to one of three different
BOOST (Pin 12):
Bootstrapped Supply to the Topside levels for the comparator. Floating Driver. A capacitor is connected between the
TRACK/SS (Pin 19):
External Tracking and Soft-Start Input. BOOST and SW pin and a Schottky diode is tied between The LTC7800 regulates the VFB voltage to the smaller of the BOOST and INTVCC pins. Voltage swing at the BOOST 0.8V or the voltage on the TRACK/SS pin. An internal 10μA pin is from INTVCC to (VIN + INTVCC). pull-up current source is connected to this pin. A capacitor
BG (Pin 13):
High Current Gate Drive for Bottom (Syn- to ground at this pin sets the ramp time to final regulated chronous) N-channel MOSFET. Voltage swing at this pin output voltage. Alternatively, a resistor divider on another is from ground to INTV voltage supply connected to this pin allows the LTC7800 CC. output to track another supply during start-up.
INTVCC (Pin 14):
Output of the Internal Linear Low Dropout Regulator. The driver and control circuits are powered from
FREQ (Pin 20):
The frequency control pin for the internal this voltage source. Must be decoupled to PGND with a VCO. Connecting the pin to GND forces the VCO to a fixed minimum of 2.2µF ceramic or other low ESR capacitor. Do low frequency of 0.94MHz. Connecting the pin to INTVCC not use the INTV forces the VCO to a fixed high frequency of 1.44MHz. CC pin for any other purpose. Other frequencies between 320kHz and 2.25MHz can be
EXTVCC (Pin 15):
External Power Input to an Internal LDO programmed by using a resistor between FREQ and GND. Connected to INTVCC. This LDO supplies INTVCC power, An internal 20µA pull-up current develops the voltage to bypassing the internal LDO powered from VIN whenever be used by the VCO to control the frequency. EXTVCC is higher than 4.7V. See EXTVCC Connection in the Applications Information section. Do not float or exceed 14V on this pin. 7800f For more information www.linear.com/LTC7800 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions FUNCTIONAL Diagram Operation Applications Information Typical Application Related Parts
PIN FUNCTIONS PGOOD (Pin 9):
Open-Drain Logic Output. PGOOD is pulled
PGND (Pin 16):
Driver Power Ground. Connects to the to ground when the voltage on the VFB pin is not within source of bottom (synchronous) N-channel MOSFET and 10% of its set point. the (–) terminal of CIN.
TG (Pin 10):
High Current Gate Drives for Top N-channel
VIN (Pin 17):
Main Supply Pin. A bypass capacitor should MOSFET. This is the output of floating driver with a volt- be tied between this pin and the SGND pins. age swing equal to INTVCC superimposed on the switch
I
node voltage SW.
LIM (Pin 18):
Current Comparator Sense Voltage Range Inputs. Tying this pin to SGND, FLOAT or INTVCC sets the
SW (Pin 11):
Switch Node Connection to Inductor. maximum current sense threshold to one of three different
BOOST (Pin 12):
Bootstrapped Supply to the Topside levels for the comparator. Floating Driver. A capacitor is connected between the
TRACK/SS (Pin 19):
External Tracking and Soft-Start Input. BOOST and SW pin and a Schottky diode is tied between The LTC7800 regulates the VFB voltage to the smaller of the BOOST and INTVCC pins. Voltage swing at the BOOST 0.8V or the voltage on the TRACK/SS pin. An internal 10μA pin is from INTVCC to (VIN + INTVCC). pull-up current source is connected to this pin. A capacitor
BG (Pin 13):
High Current Gate Drive for Bottom (Syn- to ground at this pin sets the ramp time to final regulated chronous) N-channel MOSFET. Voltage swing at this pin output voltage. Alternatively, a resistor divider on another is from ground to INTV voltage supply connected to this pin allows the LTC7800 CC. output to track another supply during start-up.
INTVCC (Pin 14):
Output of the Internal Linear Low Dropout Regulator. The driver and control circuits are powered from
FREQ (Pin 20):
The frequency control pin for the internal this voltage source. Must be decoupled to PGND with a VCO. Connecting the pin to GND forces the VCO to a fixed minimum of 2.2µF ceramic or other low ESR capacitor. Do low frequency of 0.94MHz. Connecting the pin to INTVCC not use the INTV forces the VCO to a fixed high frequency of 1.44MHz. CC pin for any other purpose. Other frequencies between 320kHz and 2.25MHz can be
EXTVCC (Pin 15):
External Power Input to an Internal LDO programmed by using a resistor between FREQ and GND. Connected to INTVCC. This LDO supplies INTVCC power, An internal 20µA pull-up current develops the voltage to bypassing the internal LDO powered from VIN whenever be used by the VCO to control the frequency. EXTVCC is higher than 4.7V. See EXTVCC Connection in the Applications Information section. Do not float or exceed 14V on this pin. 7800f For more information www.linear.com/LTC7800 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions FUNCTIONAL Diagram Operation Applications Information Typical Application Related Parts