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ILC6376SO33 数据表(PDF) 6 Page - Fairchild Semiconductor |
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ILC6376SO33 数据表(HTML) 6 Page - Fairchild Semiconductor |
6 / 12 page External component selection Proper selection of external components is important for achieving high performance. The output inductor selected should have low DC resistance on the order of 0.2 Ω or less and saturation current rating of 1A or higher. Recommended inductors are Sumida CD54 (22µH, 0.18 Ω max DC resis- tance) or Coilcraft DO3308P-223 (22µH, 0.18 Ω max DC resistance) or equivalent. The catch diode should be a schottky diode with low forward drop and rated at 1A or greater current, SS12 or it’s equiva- lent is recommended. Input and output capacitors should be tantalum capacitors with low equivalent series resistance (ESR) and voltage rat- ing higher than the actual application. Soft-start Pin 4 of ILC6376/77 functions as the soft-start pin as well as the shutdown pin. A soft-start capacitor (from pin 4 to ground) controls the rate at which the power supply starts up; thus preventing large overshoots at the output as well as large in-rush current. The value for CSS should be 100pF or greater. Shutdown The ILC6376/77 is placed in shutdown mode by taking pin 4 to ground. In shutdown, the quiescent current of the device is under 2µA. When using the shutdown feature, pin 4 must be driven from an open collector or open drain output without employing an external pull-up resistor, as shown in figure 2. Over-current and short-circuit protection In the event of an over-current or short-circuit condition, the ILC6376/77 cycles the soft-start pin in a hiccup mode to pro- vide fault protection. When the output voltage decreases due to overload, the ILC6376/77 will operate continuously at the maximum duty cycle. If the period of maximum duty cycle operation exceeds TPRO (typically 5 msec), pin 4 will be pulled low; thus discharging the external soft-start capacitor CSS. This action inhibits the regulator’s PWM action. Next, the ILC6376/77’s soft-start circuitry starts recharging CSS and initiates a controlled start-up. If the overload condition continues to exist, the above sequence of events will repeat; thus continuing to cycle the soft-start function. Note that very little power is dissipated with this method of fault protection versus constant current limit protection. Even though the internal power MOSFET is pulsed on and off at high peak current, the DC current is low; thus leading to low power dissipation even under short-circuit conditions. Keep in mind that the duration of maximum duty cycle condition is used to trigger the ILC6376/77’s fault protec- tion circuit. As such, a small input-output (VIN - VOUT) differential voltage may trigger the device’s fault protec- tion circuitry even at low output current. Undervoltage Lockout The undervoltage lockout feature prevents faulty operation by disabling the operation of the regulator when input volt- age is below the minimum operating voltage, VUVLO. When the input voltage is lower than VUVLO the device disables the internal P-channel MOSFET and provides “high” output at both EXT1 and EXT2 outputs. + VOUT ILC6376/77 (TOP VIEW) 3 4 5 1 2 6 7 8 + CL VIN S/D CSS SD1 L *CIN Fig 1. Typical step-down DC-DC converter application SD1: SS12 Schottky Diode (FAIRCHILD) CL: 10V/47µF Tantalum Capacitor (NICHICON, F93) CSS: 4700pF Ceramic Capacitor CIN: 16V / 10µF Tantalum Capacitor (NICHICON, F93) 22 µH 47 µF 10 µF Figure 1 shows a typical fixed output voltage step-down DC-DC converter application circuit for ILC6376/77SOXX. ILC6376/77 6 ©2001 Fairchild Semiconductor Corporation |
类似零件编号 - ILC6376SO33 |
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类似说明 - ILC6376SO33 |
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