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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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LTM8005 датащи(PDF) 13 Page - Linear Technology |
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LTM8005 датащи(HTML) 13 Page - Linear Technology |
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13 / 26 page  LTM8005 13 8005f For more information www.linear.com/LTM8005 APPLICATIONS INFORMATION Example: Calculate the resistor values required to increase the VOUT range of a boost LED driver to 7.5:1 and have OPENLED occur when VOUT is 38V: Step 1: Choose R10 = 374k Step 2: VOUTMIN = 38/7.5 = 5.1 Step 3: R11= 1.7 • 374kΩ 1.65 • 38 ( ) – 0.8 • 5.1 ( ) – 1.7 = 11.2kΩ Use R11 = 11.3k. R12 = 1.7 • 374kΩ 0.35 • 38 ( ) – 1.2 • 5.1 ( ) = 88.6kΩ Use R12 = 88.7K. The resistor values for R14 and R15 in Figure 6 can be calculated as shown below. See the example that follows for a suggested R13 value. R14 = 1.7 • R13 1.65 • VOUTMAX ( ) – 0.8 • VOUTMIN ( ) – 0.85 • VBE(Q1) ( ) R15 = 1.7 • R13 0.35 • VOUTMAX ( ) – 1.2 • VOUTMIN ( ) – 0.85 • VBE(Q1) ( ) Example: Calculate the resistor values required to increase the VOUT range of a buck-boost mode LED driver to 5:1 and have OPENLED occur when VOUT is 17V. Use VBE(Q1) =0.7V: Step 1: Choose R13 = 187k Step 2: VOUTMIN = 17/5 = 3.4 Step 3: R14 = 1.7 • 187kΩ 1.65 • 17 ( ) – 0.8 • 3.4 ( ) – 0.85 • 0.7 ( ) = 12.9kΩ Use R14 = 12.7k R15 = 1.7 • 187kΩ 0.35 • 17 ( ) – 1.2 • 3.4 ( ) – 0.85 • 0.7 ( ) = 249kΩ Use R15 = 249k LED Overcurrent Protection Feature The LTM8005 has an overload protection feature inde- pendent of the output LED current regulation. This feature prevents the development of excessive switching currents and protects the power components. The overload protec- tion threshold (2.4A typical) is designed to be 50% higher than the default LED current sense threshold. Once the LED overcurrent is detected, the internal power switch is turned off to stop switching, the PWM MOSFET is turned off to disconnect the LED array from the power path, and fault protection is initiated via the SS pin. An anti-parallel Schottky or ultrafast diode D2 should be connected as shown in Figure 7 to protect the LED node from swinging well below ground when being shorted to ground through a long cable. The internal protection loop takes a finite amount of time to respond to the overload, so the diode is recommended if the system must survive an overload on the LED string. LTM8005 LED GND D2 8005 F07 LED STRING PARASITIC INDUCTANCE OF LONG CABLE Figure7. Connect an Anti-Parallel Diode D2 from LED to GND to Protect the LTM8005 from Negative Voltage Swings when the Connecting to a LED String through a Long Cable |
Аналогичный номер детали - LTM8005 |
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Аналогичное описание - LTM8005 |
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