Datasheet LT3798 (Analog Devices) - 6
| Hersteller | Analog Devices |
| Beschreibung | Isolated No Opto-Coupler Flyback Controller with Active PFC |
| Seiten / Seite | 20 / 6 — TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. … |
| Dateiformat / Größe | PDF / 423 Kb |
| Dokumentensprache | Englisch |
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Power Factor vs Input Voltage
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LT3798
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Power Factor vs Input Voltage Efficiency vs Input Voltage
1.00 100 PAGE 17 SCHEMATIC: 0.99 UNIVERSAL 0.98 90 0.97 0.96 0.95 80 0.94 POWER FACTOR EFFICIENCY (%) 0.93 70 0.92 0.91 PAGE 17 SCHEMATIC: UNIVERSAL 0.90 60 90 110 130 150 170 190 210 230 250 270 90 110 130 150 170 190 210 230 250 270 VIN (VAC) VIN (VAC) 3798 G15 3798 G16
PIN FUNCTIONS CTRL1, CTRL2, CTRL3 (Pin 1, Pin 2, Pin 3):
Current
FB (Pin 9):
Voltage Loop Feedback Pin. FB is used to Output Adjustment Pins. These pins control the output regulate the output voltage by sampling the third wind- current. The lowest value out of the three CTRL inputs is ing. If the converter is used in current mode, the FB pin compared to negative input of the operational amplifier. will normally be at a voltage level lower than 1.25V, and
V
will reach the steady state of 1.25V if it detects an open
REF (Pin 4):
Voltage Reference Output Pin. Typically 2V. This pin drives a resistor divider for the CTRL pin, either output condition. for analog dimming or for temperature limit/compensation
DCM (Pin 10):
Discontinuous Conduction Mode Detection of output load. Can supply up to 200µA. Pin. Connect a capacitor and resistor in series with this
OVP (Pin 5):
Overvoltage Protection. This pin accepts a pin to the third winding. DC voltage to compare to the sample and hold’s voltage
VIN (Pin 11):
Input Voltage. This pin supplies current to output information. When output voltage information is the internal start-up circuitry and to the INTVCC LDO. This above the OVP, the part divides the minimum switching pin must be locally bypassed with a capacitor. A 42V shunt frequency by 8, around 500Hz. This protects devices con- regulator is internally connected to this pin. nected to the output. This also allows the part to operate
EN/UVLO (Pin 12):
Enable/Undervoltage Lockout. A resis- with very little power consumption with no load to meet tor divider connected to V energy star requirements. IN is tied to this pin to program the minimum input voltage at which the LT3798 will turn
VC (Pin 6):
Compensation Pin for Internal Error Amplifier. on. When below 1.25V, the part will draw 60µA with most Connect a series RC from this pin to ground to compensate of the internal circuitry disabled and a 10µA hysteresis the switching regulator. A 100pF capacitor in parallel helps current will be pulled out of the EN/UVLO pin. When above eliminate noise. 1.25V, the part will be enabled and begin to switch and the
COMP+, COMP– (Pin 7, Pin 8):
Compensation Pins for 10µA hysteresis current is turned off. Internal Error Amplifier. Connect a capacitor between these
INTVCC (Pin 13):
Regulated Supply for Internal Loads two pins to compensate the internal feedback loop. and GATE Driver. Supplied from VIN and regulates to 10V (typical). INTVCC must be bypassed with a 4.7µF capacitor placed close to the pin. 3798fa 6 Document Outline Description Features Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Typical Applications Package Description Revision History Typical Application Related Parts
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Power Factor vs Input Voltage Efficiency vs Input Voltage
1.00 100 PAGE 17 SCHEMATIC: 0.99 UNIVERSAL 0.98 90 0.97 0.96 0.95 80 0.94 POWER FACTOR EFFICIENCY (%) 0.93 70 0.92 0.91 PAGE 17 SCHEMATIC: UNIVERSAL 0.90 60 90 110 130 150 170 190 210 230 250 270 90 110 130 150 170 190 210 230 250 270 VIN (VAC) VIN (VAC) 3798 G15 3798 G16
PIN FUNCTIONS CTRL1, CTRL2, CTRL3 (Pin 1, Pin 2, Pin 3):
Current
FB (Pin 9):
Voltage Loop Feedback Pin. FB is used to Output Adjustment Pins. These pins control the output regulate the output voltage by sampling the third wind- current. The lowest value out of the three CTRL inputs is ing. If the converter is used in current mode, the FB pin compared to negative input of the operational amplifier. will normally be at a voltage level lower than 1.25V, and
V
will reach the steady state of 1.25V if it detects an open
REF (Pin 4):
Voltage Reference Output Pin. Typically 2V. This pin drives a resistor divider for the CTRL pin, either output condition. for analog dimming or for temperature limit/compensation
DCM (Pin 10):
Discontinuous Conduction Mode Detection of output load. Can supply up to 200µA. Pin. Connect a capacitor and resistor in series with this
OVP (Pin 5):
Overvoltage Protection. This pin accepts a pin to the third winding. DC voltage to compare to the sample and hold’s voltage
VIN (Pin 11):
Input Voltage. This pin supplies current to output information. When output voltage information is the internal start-up circuitry and to the INTVCC LDO. This above the OVP, the part divides the minimum switching pin must be locally bypassed with a capacitor. A 42V shunt frequency by 8, around 500Hz. This protects devices con- regulator is internally connected to this pin. nected to the output. This also allows the part to operate
EN/UVLO (Pin 12):
Enable/Undervoltage Lockout. A resis- with very little power consumption with no load to meet tor divider connected to V energy star requirements. IN is tied to this pin to program the minimum input voltage at which the LT3798 will turn
VC (Pin 6):
Compensation Pin for Internal Error Amplifier. on. When below 1.25V, the part will draw 60µA with most Connect a series RC from this pin to ground to compensate of the internal circuitry disabled and a 10µA hysteresis the switching regulator. A 100pF capacitor in parallel helps current will be pulled out of the EN/UVLO pin. When above eliminate noise. 1.25V, the part will be enabled and begin to switch and the
COMP+, COMP– (Pin 7, Pin 8):
Compensation Pins for 10µA hysteresis current is turned off. Internal Error Amplifier. Connect a capacitor between these
INTVCC (Pin 13):
Regulated Supply for Internal Loads two pins to compensate the internal feedback loop. and GATE Driver. Supplied from VIN and regulates to 10V (typical). INTVCC must be bypassed with a 4.7µF capacitor placed close to the pin. 3798fa 6 Document Outline Description Features Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Typical Applications Package Description Revision History Typical Application Related Parts