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 — TYPICAL PERFORMANCE CHARACTERISTICS. Top FET Current Limit. vs Duty … |
| Revision | B |
| File Format / Size | PDF / 2.4 Mb |
| Document Language | English |
TYPICAL PERFORMANCE CHARACTERISTICS. Top FET Current Limit. vs Duty Cycle. Switch Drop vs Temperature
Model Line for this Datasheet
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 Rev. B For more information www.analog.com 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Applications Related Parts
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 Rev. B For more information www.analog.com 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Applications Related Parts
