Datasheet LT3481 (Analog Devices) - 7
| Hersteller | Analog Devices |
| Beschreibung | 36V, 2A, 2.8MHz Step-Down Switching Regulator with 50µA Quiescent Current |
| Seiten / Seite | 24 / 7 — PIN FUNCTIONS. BD (Pin 1):. PG (Pin 6):. BOOST (Pin 2):. BIAS (Pin 7):. … |
| Dateiformat / Größe | PDF / 315 Kb |
| Dokumentensprache | Englisch |
PIN FUNCTIONS. BD (Pin 1):. PG (Pin 6):. BOOST (Pin 2):. BIAS (Pin 7):. SW (Pin 3):. VIN (Pin 4):. FB (Pin 8):. RUN/SS (Pin 5):
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LT3481
PIN FUNCTIONS BD (Pin 1):
This pin connects to the anode of the boost
PG (Pin 6):
The PG pin is the open-collector output of an Schottky diode. internal comparator. PG remains low until the FB pin is within 10% of the fi nal regulation voltage. PG output is
BOOST (Pin 2):
This pin is used to provide a drive valid when V voltage, higher than the input voltage, to the internal bipolar IN is above 3.5V and RUN/SS is high. NPN power switch.
BIAS (Pin 7):
The BIAS pin supplies the current to the LT3481’s internal regulator. Tie this pin to the lowest
SW (Pin 3):
The SW pin is the output of the internal power available voltage source above 3V (typically V switch. Connect this pin to the inductor, catch diode and OUT). This architecture increases effi ciency especially when the input boost capacitor. voltage is much higher than the output.
VIN (Pin 4):
The VIN pin supplies current to the LT3481’s
FB (Pin 8):
The LT3481 regulates the FB pin to 1.265V. internal regulator and to the internal power switch. This Connect the feedback resistor divider tap to this pin. pin must be locally bypassed.
V RUN/SS (Pin 5):
The RUN/SS pin is used to put the
C (Pin 9):
The VC pin is the output of the internal error amplifi er. The voltage on this pin controls the peak switch LT3481 in shutdown mode. Tie to ground to shut down current. Tie an RC network from this pin to ground to the LT3481. Tie to 2.3V or more for normal operation. If compensate the control loop. the shutdown feature is not used, tie this pin to the VIN pin. RUN/SS also provides a soft-start function; see the
RT (Pin 10):
Oscillator Resistor Input. Connecting a resistor Applications Information section. to ground from this pin sets the switching frequency.
Exposed Pad (Pin 11):
Ground. The Exposed Pad must be soldered to PCB.
BLOCK DIAGRAM
VIN VIN 4 C1 BIAS – 7 INTERNAL 1.265V REF + BD 1 RUN/SS 5 3 SLOPE COMP SWITCH BOOST LATCH 2 C3 R RT OSCILLATOR Q 10 300kHz TO 2.8MHz S L1 SW R V 3 OUT T DISABLE D1 C2 SOFT-START Burst Mode DETECT PG 6 ERROR AMP VC CLAMP + 1.12V + VC 9 – – CC CF RC GND FB 11 8 R2 R1 3481 BD 3481fc 7
PIN FUNCTIONS BD (Pin 1):
This pin connects to the anode of the boost
PG (Pin 6):
The PG pin is the open-collector output of an Schottky diode. internal comparator. PG remains low until the FB pin is within 10% of the fi nal regulation voltage. PG output is
BOOST (Pin 2):
This pin is used to provide a drive valid when V voltage, higher than the input voltage, to the internal bipolar IN is above 3.5V and RUN/SS is high. NPN power switch.
BIAS (Pin 7):
The BIAS pin supplies the current to the LT3481’s internal regulator. Tie this pin to the lowest
SW (Pin 3):
The SW pin is the output of the internal power available voltage source above 3V (typically V switch. Connect this pin to the inductor, catch diode and OUT). This architecture increases effi ciency especially when the input boost capacitor. voltage is much higher than the output.
VIN (Pin 4):
The VIN pin supplies current to the LT3481’s
FB (Pin 8):
The LT3481 regulates the FB pin to 1.265V. internal regulator and to the internal power switch. This Connect the feedback resistor divider tap to this pin. pin must be locally bypassed.
V RUN/SS (Pin 5):
The RUN/SS pin is used to put the
C (Pin 9):
The VC pin is the output of the internal error amplifi er. The voltage on this pin controls the peak switch LT3481 in shutdown mode. Tie to ground to shut down current. Tie an RC network from this pin to ground to the LT3481. Tie to 2.3V or more for normal operation. If compensate the control loop. the shutdown feature is not used, tie this pin to the VIN pin. RUN/SS also provides a soft-start function; see the
RT (Pin 10):
Oscillator Resistor Input. Connecting a resistor Applications Information section. to ground from this pin sets the switching frequency.
Exposed Pad (Pin 11):
Ground. The Exposed Pad must be soldered to PCB.
BLOCK DIAGRAM
VIN VIN 4 C1 BIAS – 7 INTERNAL 1.265V REF + BD 1 RUN/SS 5 3 SLOPE COMP SWITCH BOOST LATCH 2 C3 R RT OSCILLATOR Q 10 300kHz TO 2.8MHz S L1 SW R V 3 OUT T DISABLE D1 C2 SOFT-START Burst Mode DETECT PG 6 ERROR AMP VC CLAMP + 1.12V + VC 9 – – CC CF RC GND FB 11 8 R2 R1 3481 BD 3481fc 7