Datasheet LT3512 (Analog Devices) - 5
| Manufacturer | Analog Devices |
| Description | Monolithic High Voltage Isolated Flyback Converter |
| Pages / Page | 26 / 5 — pin FuncTions. EN/UVLO (Pin 1):. VC (Pin 10):. C (Pin 11):. IN (Pin 3):. … |
| File Format / Size | PDF / 315 Kb |
| Document Language | English |
pin FuncTions. EN/UVLO (Pin 1):. VC (Pin 10):. C (Pin 11):. IN (Pin 3):. RREF (Pin 12):. GND (Pin 5, 8, 9):. RFB (Pin 14):
Model Line for this Datasheet
Text Version of Document
LT3512
pin FuncTions EN/UVLO (Pin 1):
Enable/Undervoltage Lockout. The EN/
VC (Pin 10):
Compensation Pin for Internal Error Amplifier. UVLO pin is used to start up the LT3512. Pull the pin to 0V Connect a series RC from this pin to ground to compensate to shut down the LT3512. This pin has an accurate 1.21V the switching regulator. An additional 100pF capacitor from threshold and can be used to program an undervoltage this pin to ground helps eliminate noise. lockout (UVLO) threshold using a resistor divider from
T
supply to ground. A 2.6μA pin current hysteresis allows
C (Pin 11):
Output Voltage Temperature Compensa- tion. Connect a resistor to ground to produce a current the programming of undervoltage lockout (UVLO) hys- proportional to absolute temperature to be sourced into teresis. EN/UVLO can be directly connected to VIN. If left the R open circuit the part will not power up. REF node. I
V
TC = 0.55V/RTC.
IN (Pin 3):
Input Supply Pin. This pin supplies current to the internal start-up circuitry, and serves as a reference
RREF (Pin 12):
Input Pin for External Ground-Referred voltage for the DCM comparator and feedback circuitry. Reference Resistor. The resistor at this pin should be 10k. Must be locally bypassed with a capacitor. For nonisolated applications, a traditional resistor voltage divider from V
GND (Pin 5, 8, 9):
Ground Pins. All three pins should be OUT may be connected to this pin. tied directly to the local ground plane.
RFB (Pin 14):
Input Pin for External Feedback Resistor. This pin is connected to the transformer primary (V
BIAS (Pin 6):
Bias Voltage. This pin supplies current to SW). The ratio of this resistor to the R the switch driver and internal circuitry of the LT3512. REF resistor, times the internal bandgap reference, determines the output volt- This pin may also be connected to VIN if a third winding age (plus the effect of any non-unity transformer turns is not used and if VIN < 20V. The part can operate down ratio). For nonisolated applications, this pin should be to 4.5V when BIAS and VIN are connected together. If a connected to V third winding is used, the BIAS voltage should be lower IN. than the input voltage and greater than 3.3V for proper
SW (Pin 16):
Switch Pin. Collector of the internal power operation. BIAS must be bypassed with a 4.7µF capacitor switch. Minimize trace area at this pin to minimize EMI placed close to the pin. and voltage spikes. 3512fb 5 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 EN/UVLO (Pin 1):
Enable/Undervoltage Lockout. The EN/
VC (Pin 10):
Compensation Pin for Internal Error Amplifier. UVLO pin is used to start up the LT3512. Pull the pin to 0V Connect a series RC from this pin to ground to compensate to shut down the LT3512. This pin has an accurate 1.21V the switching regulator. An additional 100pF capacitor from threshold and can be used to program an undervoltage this pin to ground helps eliminate noise. lockout (UVLO) threshold using a resistor divider from
T
supply to ground. A 2.6μA pin current hysteresis allows
C (Pin 11):
Output Voltage Temperature Compensa- tion. Connect a resistor to ground to produce a current the programming of undervoltage lockout (UVLO) hys- proportional to absolute temperature to be sourced into teresis. EN/UVLO can be directly connected to VIN. If left the R open circuit the part will not power up. REF node. I
V
TC = 0.55V/RTC.
IN (Pin 3):
Input Supply Pin. This pin supplies current to the internal start-up circuitry, and serves as a reference
RREF (Pin 12):
Input Pin for External Ground-Referred voltage for the DCM comparator and feedback circuitry. Reference Resistor. The resistor at this pin should be 10k. Must be locally bypassed with a capacitor. For nonisolated applications, a traditional resistor voltage divider from V
GND (Pin 5, 8, 9):
Ground Pins. All three pins should be OUT may be connected to this pin. tied directly to the local ground plane.
RFB (Pin 14):
Input Pin for External Feedback Resistor. This pin is connected to the transformer primary (V
BIAS (Pin 6):
Bias Voltage. This pin supplies current to SW). The ratio of this resistor to the R the switch driver and internal circuitry of the LT3512. REF resistor, times the internal bandgap reference, determines the output volt- This pin may also be connected to VIN if a third winding age (plus the effect of any non-unity transformer turns is not used and if VIN < 20V. The part can operate down ratio). For nonisolated applications, this pin should be to 4.5V when BIAS and VIN are connected together. If a connected to V third winding is used, the BIAS voltage should be lower IN. than the input voltage and greater than 3.3V for proper
SW (Pin 16):
Switch Pin. Collector of the internal power operation. BIAS must be bypassed with a 4.7µF capacitor switch. Minimize trace area at this pin to minimize EMI placed close to the pin. and voltage spikes. 3512fb 5 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
