Datasheet LT8645S, LT8646S (Analog Devices) - 7
| Manufacturer | Analog Devices |
| Description | 65V, 8A Synchronous Step-Down Silent Switcher 2 with 2.5μA Quiescent Current |
| Pages / Page | 30 / 7 — Top FET Current Limit. vs Duty Cycle. Switch Drop vs Temperature. Switch … |
| File Format / Size | PDF / 457 Kb |
| Document Language | English |
Top FET Current Limit. vs Duty Cycle. Switch Drop vs Temperature. Switch Drop vs Switch Current. Dropout Voltage. Minimum On-Time
Text Version of Document
LT8645S/LT8646S TYPICAL PERFORMANCE CHARACTERISTICS
Top FET Current Limit vs Duty Cycle Top FET Current Limit Switch Drop vs Temperature
15.0 16 100 SWITCH CURRENT = 1A 14.5 80 14.0 15 13.5 5% DC 60 13.0 14 TOP SWITCH 12.5 40 CURRENT LIMIT (A) CURRENT LIMIT (A) SWITCH DROP (mV) 12.0 13 BOTTOM SWITCH 20 11.5 11.0 12 0 0.1 0.3 0.5 0.7 0.9 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 DUTY CYCLE TEMPERATURE (°C) TEMPERATURE (°C) 8645S G19 8645S G20 8645S G21
Switch Drop vs Switch Current Dropout Voltage Minimum On-Time
350 400 50 VIN = 5V BURST MODE OPERATION V 300 350 OUT SET TO REGULATE AT 5V PULSE–SKIPPING MODE L = XEL6060, 1µH 45 300 250 250 200 TOP SWITCH 40 TAGE (mV) 200 150 150 35 SWITCH DROP (mV) 100 DROPOUT VOL 100 MINIMUM ON-TIME (ns) BOTTOM SWITCH 30 50 I 50 LOAD = 3A VOUT = 0.97V fSW = 2.2MHz 0 0 25 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 –50 –25 0 25 50 75 100 125 SWITCH CURRENT (A) LOAD CURRENT (A) TEMPERATURE (°C) 8645S G22 8645S G23 8645S G24
Minimum Load to Full Frequency Switching Frequency Burst Frequency (Pulse-Skipping Mode)
740 1200 400 RT = 60.4k FRONT PAGE APPLICATION 730 350 V 1000 OUT = 5V fSW = 1MHz 720 300 VSYNC = Float 800 710 250 700 600 200 690 150 400 LOAD CURRENT (mA) 680 100 SWITCHING FREQUENCY (kHz) SWITCHING FREQUENCY (kHz) FRONT PAGE APPLICATION 200 670 VIN = 12V 50 VOUT = 5V 660 0 0 –50 –25 0 25 50 75 100 125 0 100 200 300 400 500 600 5 15 25 35 45 55 65 TEMPERATURE (°C) LOAD CURRENT (mA) INPUT VOLTAGE (V) 8645S G25 8645S G26 8645S G27 8645Sfa For more information www.linear.com/LT8645S 7
Top FET Current Limit vs Duty Cycle Top FET Current Limit Switch Drop vs Temperature
15.0 16 100 SWITCH CURRENT = 1A 14.5 80 14.0 15 13.5 5% DC 60 13.0 14 TOP SWITCH 12.5 40 CURRENT LIMIT (A) CURRENT LIMIT (A) SWITCH DROP (mV) 12.0 13 BOTTOM SWITCH 20 11.5 11.0 12 0 0.1 0.3 0.5 0.7 0.9 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 DUTY CYCLE TEMPERATURE (°C) TEMPERATURE (°C) 8645S G19 8645S G20 8645S G21
Switch Drop vs Switch Current Dropout Voltage Minimum On-Time
350 400 50 VIN = 5V BURST MODE OPERATION V 300 350 OUT SET TO REGULATE AT 5V PULSE–SKIPPING MODE L = XEL6060, 1µH 45 300 250 250 200 TOP SWITCH 40 TAGE (mV) 200 150 150 35 SWITCH DROP (mV) 100 DROPOUT VOL 100 MINIMUM ON-TIME (ns) BOTTOM SWITCH 30 50 I 50 LOAD = 3A VOUT = 0.97V fSW = 2.2MHz 0 0 25 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 –50 –25 0 25 50 75 100 125 SWITCH CURRENT (A) LOAD CURRENT (A) TEMPERATURE (°C) 8645S G22 8645S G23 8645S G24
Minimum Load to Full Frequency Switching Frequency Burst Frequency (Pulse-Skipping Mode)
740 1200 400 RT = 60.4k FRONT PAGE APPLICATION 730 350 V 1000 OUT = 5V fSW = 1MHz 720 300 VSYNC = Float 800 710 250 700 600 200 690 150 400 LOAD CURRENT (mA) 680 100 SWITCHING FREQUENCY (kHz) SWITCHING FREQUENCY (kHz) FRONT PAGE APPLICATION 200 670 VIN = 12V 50 VOUT = 5V 660 0 0 –50 –25 0 25 50 75 100 125 0 100 200 300 400 500 600 5 15 25 35 45 55 65 TEMPERATURE (°C) LOAD CURRENT (mA) INPUT VOLTAGE (V) 8645S G25 8645S G26 8645S G27 8645Sfa For more information www.linear.com/LT8645S 7
