Electronic Components Datasheet Search |
|
LT3478EFE-1 Datasheet(PDF) 7 Page - Linear Technology |
|
LT3478EFE-1 Datasheet(HTML) 7 Page - Linear Technology |
7 / 24 page LT3478/LT3478-1 7 34781f PI FU CTIO S SW (Pins 1, 2): Switch Pin. Collector of the internal NPN power switch. Both pins are fused together inside the IC. Connect the inductor and diode here and minimize the metal trace area connected to this pin to minimize EMI. VIN (Pin 3): Input Supply. Must be locally bypassed with a capacitor to ground. VS (Pin 4): Inductor Supply. Must be locally bypassed with a capacitor to ground. Can be shorted to VIN if only one supply is available (see L (Pin 5) function). L (Pin 5): Inductor Pin. An internal resistor between VS and L pins monitors inductor current to protect against inrush current. Exceeding 6A immediately turns off the internal NPN power switch and discharges the soft-start pin. Input current monitoring can be disabled by connect- ing the inductor power supply directly to the L pin and leaving the VS pin open (requires local bypass capacitor to GND on L pin; not VS pin). VOUT (Pin 6): Output voltage of the converter. Connect a capacitor from this pin to ground. Internal circuitry moni- tors VOUT for protection against open LED faults. LED (Pin 7): Connect the LED string from this pin to ground. An internal (LT3478-1)/external (LT3478) resistor between the VOUT and LED pins senses LED current for accurate control. OVPSET (Pin 8): Programs VOUT overvoltage protection level (OVP) to protect against open LED faults. OVP = (OVPSET • 41)V. OVPSET range is 0.3V to 1V for an OVP range of typically 12.3V to 41V. VC (Pin 9): Output of the transconductance error amplifier and compensation pin for the converter regulation loop. VREF (Pin 10): Bandgap Voltage Reference. This pin can supply up to 100µA. Can be used to program CTRL1, CTRL2, OVPSET pin voltages using resistor dividers to ground. ⎯S⎯H⎯D⎯N (Pin 11): The ⎯S⎯H⎯D⎯N pin has an accurate 1.4V threshold and can be used to program an undervoltage lockout (UVLO) threshold for system input supply using a resistor divider from supply to ground. A 10µA pin current hysteresis allows programming of undervoltage lockout (UVLO) hysteresis. ⎯S⎯H⎯D⎯N above 1.4V turns the part on and removes a 10µA sink current from the pin. ⎯S⎯H⎯D⎯N = 0V reduces VIN current < 3µA. ⎯S⎯H⎯D⎯N can be directly connected to VIN. If left open circuit the part will be turned off. CTRL1 (Pin 12): CTRL1 pin voltage is used to program maximum LED current (CTRL2 = VREF). CTRL1 voltage can be set by a resistor divider from VREF or an external voltage source. Maximum LED current is given by: (LT3478-1) Max LED Current = Min(CTRL1, 1.05) Amps () (, . ) • . LT Max LED Current Min CTRL RSE 3478 105 01 = N NSE Amps (linear for 0.1V < CTRL1< 0.95V ; CTRL2 = VREF) For maxi- mum LED current, short CTRL1 and CTRL2 pins to VREF. CTRL2 (Pin 13): The CTRL2 pin is available for program- ming a decrease in LED current versus temperature (setting temperature breakpoint and slope). This feature allows the output LED(s) to be programmed for maximum allowable current without damage at higher temperatures. This maximizes LED usage and increases reliability. A CTRL2 voltage with negative temperature coefficient is created using an external resistor divider from VREF with temperature dependant resistance. If not used, CTRL2 should be tied to VREF. PWM (Pin 14): Input pin for PWM dimming control. Above 1V allows converter switching and below 1V disables switching with VC pin level maintained. With an external MOSFET placed in series with the ground side of the LED string, a PWM signal driving the PWM pin and MOSFET gate provides accurate dimming control. The PWM signal can be driven from 0V to 15V. If unused, the pin should be connected to VREF. RT (Pin 15): A resistor to ground programs switching frequency between 200kHz and 2.25MHz. SS (Pin 16): Soft-Start Pin. Placing a capacitor here pro- grams soft-start timing to limit inductor inrush current during start-up due to the converter. When inductor current |
Similar Part No. - LT3478EFE-1 |
|
Similar Description - LT3478EFE-1 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |