Datasheet LT8303 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | 100VIN Micropower Isolated Flyback Converter with 150V/450mA Switch |
| Pages / Page | 24 / 10 — applicaTions inForMaTion. Figure 1. Output Power for 3.3V Output. Figure … |
| File Format / Size | PDF / 1.2 Mb |
| Document Language | English |
applicaTions inForMaTion. Figure 1. Output Power for 3.3V Output. Figure 2. Output Power for 5V Output
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LT8303
applicaTions inForMaTion
6 6 MAXIMUM MAXIMUM N = 8:1 5 OUTPUT N = 12:1 5 OUTPUT POWER POWER N = 6:1 N = 8:1 4 4 N = 6:1 N = 4:1 3 3 N = 4:1 2 N = 2:1 2 OUTPUT POWER (W) OUTPUT POWER (W) 1 1 ASSUME 80% EFFICIENCY ASSUME 85% EFFICIENCY 0 0 0 20 40 60 80 100 0 20 40 60 80 100 INPUT VOLTAGE (V) INPUT VOLTAGE (V) 8303 F01 8303 F02
Figure 1. Output Power for 3.3V Output Figure 2. Output Power for 5V Output
6 6 MAXIMUM MAXIMUM N = 4:1 N = 2:1 OUTPUT OUTPUT 5 5 POWER N = 3:1 POWER N = 3:2 4 4 N = 2:1 N = 1:1 3 3 N = 1:1 N = 1:2 2 2 OUTPUT POWER (W) OUTPUT POWER (W) 1 1 ASSUME 85% EFFICIENCY ASSUME 85% EFFICIENCY 0 0 0 20 40 60 80 100 0 20 40 60 80 100 INPUT VOLTAGE (V) INPUT VOLTAGE (V) 8303 F03 8303 F04
Figure 3. Output Power for 12V Output Figure 4. Output Power for 24V Output Primary Inductance Requirement
In addition to the primary inductance requirement for The LT8303 obtains output voltage information from the the minimum switch-off time, the LT8303 has minimum reflected output voltage on the SW pin. The conduction switch-on time that prevents the chip from turning on of secondary current reflects the output voltage on the the power switch shorter than approximately 160ns. This primary SW pin. The sample-and-hold error amplifier needs minimum switch-on time is mainly for leading-edge blank- a minimum 350ns to settle and sample the reflected output ing the initial switch turn-on current spike. If the inductor voltage. In order to ensure proper sampling, the second- current exceeds the desired current limit during that time, ary winding needs to conduct current for a minimum of oscillation may occur at the output as the current control 350ns. The following equation gives the minimum value loop will lose its ability to regulate. Therefore, the following for primary-side magnetizing inductance: equation relating to maximum input voltage must also be followed in selecting primary-side magnetizing inductance: t ( ) L OFF(MIN) • NPS • VOUT + VF tON(MIN) • VIN(MAX) PRI ≥ I LPRI ≥ SW(MIN) I SW(MIN) tOFF(MIN) = Minimum switch-off time = 350ns tON(MIN) = Minimum Switch-On Time = 160ns ISW(MIN) = Minimum switch current limit = 105mA 8303fa 10 For more information www.linear.com/LT8303 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 Typical Application Related Parts
applicaTions inForMaTion
6 6 MAXIMUM MAXIMUM N = 8:1 5 OUTPUT N = 12:1 5 OUTPUT POWER POWER N = 6:1 N = 8:1 4 4 N = 6:1 N = 4:1 3 3 N = 4:1 2 N = 2:1 2 OUTPUT POWER (W) OUTPUT POWER (W) 1 1 ASSUME 80% EFFICIENCY ASSUME 85% EFFICIENCY 0 0 0 20 40 60 80 100 0 20 40 60 80 100 INPUT VOLTAGE (V) INPUT VOLTAGE (V) 8303 F01 8303 F02
Figure 1. Output Power for 3.3V Output Figure 2. Output Power for 5V Output
6 6 MAXIMUM MAXIMUM N = 4:1 N = 2:1 OUTPUT OUTPUT 5 5 POWER N = 3:1 POWER N = 3:2 4 4 N = 2:1 N = 1:1 3 3 N = 1:1 N = 1:2 2 2 OUTPUT POWER (W) OUTPUT POWER (W) 1 1 ASSUME 85% EFFICIENCY ASSUME 85% EFFICIENCY 0 0 0 20 40 60 80 100 0 20 40 60 80 100 INPUT VOLTAGE (V) INPUT VOLTAGE (V) 8303 F03 8303 F04
Figure 3. Output Power for 12V Output Figure 4. Output Power for 24V Output Primary Inductance Requirement
In addition to the primary inductance requirement for The LT8303 obtains output voltage information from the the minimum switch-off time, the LT8303 has minimum reflected output voltage on the SW pin. The conduction switch-on time that prevents the chip from turning on of secondary current reflects the output voltage on the the power switch shorter than approximately 160ns. This primary SW pin. The sample-and-hold error amplifier needs minimum switch-on time is mainly for leading-edge blank- a minimum 350ns to settle and sample the reflected output ing the initial switch turn-on current spike. If the inductor voltage. In order to ensure proper sampling, the second- current exceeds the desired current limit during that time, ary winding needs to conduct current for a minimum of oscillation may occur at the output as the current control 350ns. The following equation gives the minimum value loop will lose its ability to regulate. Therefore, the following for primary-side magnetizing inductance: equation relating to maximum input voltage must also be followed in selecting primary-side magnetizing inductance: t ( ) L OFF(MIN) • NPS • VOUT + VF tON(MIN) • VIN(MAX) PRI ≥ I LPRI ≥ SW(MIN) I SW(MIN) tOFF(MIN) = Minimum switch-off time = 350ns tON(MIN) = Minimum Switch-On Time = 160ns ISW(MIN) = Minimum switch current limit = 105mA 8303fa 10 For more information www.linear.com/LT8303 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 Typical Application Related Parts
