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AD8240YRM-REEL Fiches technique(PDF) 6 Page - Analog Devices |
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AD8240YRM-REEL Fiches technique(HTML) 6 Page - Analog Devices |
6 / 12 page AD8240 Rev. 0 | Page 6 of 12 USING/EVALUATING THE AD8240 LED DRIVER MONITOR Figure 3 shows a connection diagram for a typical application. SETUP In order to set up and evaluate the AD8240, the following components and equipment are needed: • A shunt resistor (typically 0.1 Ω to 0.5 Ω depending on the load). See the Shunt Resistor Selection section. • A transistor (the type depends on the load) • Two capacitors • LED load • 5 V reference voltage • 9 V to 27 V supply • Oscilloscope • Digital voltmeter (DVM) Shunt Resistor Selection The shunt resistor is chosen by the equation LOAD SHUNT I R V 2 . 0 ≤ For example if the load is expected to be 500 mA, the shunt value should be equal to or less than 0.4 Ω. This keeps the output of the current sense amplifier from being greater than 4.8 V in normal operation to prevent noise from causing the output to latch off. Circuit Configuration Connect the pass transistor, capacitors, and LED load(s) as shown in Figure 3. It is important to note that the value of CM should be at least 22 nF to ensure circuit stability. The LED lamp should be configured to expect 12 V. This is the result of selecting the series/parallel combinations of LEDs and series resistors. The series resistors can be used to adjust for LED supplier brightness variations from lot to lot. Connect 5 V to Pin 2 (5 V reference) and at least 9 V to Pin 5 (VPLUS). It may be necessary to raise the VPLUS voltage to more than 13 V, depending on the drop across the pass transistor, for the output to be regulated at 12 V. This varies according to the application and the pass transistor type. . CL 47nF R1 350k Ω R2 250k Ω LATCH-OFF DRIVER RSENSE 10k Ω GND 1 2 3 4 5 7 6 8 VO VSENSE 5V REFERENCE PWM VPLUS BASE SHUNT VBATT CM 22nF RSHUNT Figure 3. Connections for Typical Applications |
Numéro de pièce similaire - AD8240YRM-REEL |
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Description similaire - AD8240YRM-REEL |
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