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LM3570 数据表(PDF) 4 Page - National Semiconductor (TI) |
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LM3570 数据表(HTML) 4 Page - National Semiconductor (TI) |
4 / 13 page Electrical Characteristics(Notes 2, 8) (Continued) Limits in standard typeface and typical values apply for T J =25 oC. Limits in boldface type apply over the operating junction temperature range. Unless otherwise noted, specifications apply to the LM3570 typical Application Circuit (pg.1) with: V IN = 3.6V, V EN = 3.0V, VPWM = 3.0V, VDX=3.6V, RSET = 6.25k Ω,C 1=C2=1.0µF, CIN=2.2µF, COUT=3.3µF(Note 9) Symbol Parameter Condition Min Typ Max Units V SET I SET Pin Voltage 1.25 V I Dx /ISET Output Current to Current Set Ratio 100 f SW Switching Frequency (Note 15) 3.0V ≤ V IN ≤ 5.5V 300 500 665 kHz t START Start-up Time I Dx = 90% steady state 250 µs EN and PWM Pin Characteristics V EN-IL Enable Pin Logic Low 3.0V ≤ V IN ≤ 5.5V 0 0.5 V V EN-IH Enable Pin Logic High 3.0V ≤ V IN ≤ 5.5V 1.0 V IN V V PWM-IL PWM Pin Logic Low 3.0V ≤ V IN ≤ 5.5V 0 0.5 V V PWM-IH PWM PinLogic High 3.0V ≤ V IN ≤ 5.5V 1.0 V IN V I LEAK-EN Enable Pin Leakage Current (Note 14) 10 µA I LEAK-PWM PWM Pin Leakage Current (Note 14) 10 µA Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics tables. Note 2: All voltages are with respect to the potential at the GND pin. Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=150 oC (typ.) and disengages at TJ=140 oC (typ.). Note 4: For detailed soldering specifications and information, please refer to National Semiconductor Application Note 1187: Leadless Leadframe Package (LLP). Note 5: The Human body model is a 100pF capacitor discharged through a 1.5k Ω resistor into each pin. (MIL-STD-883 3015.7) The machine model is a 200pF capacitor discharged directly into each pin. (EAIJ) Note 6: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125 oC), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (θJA), as given by the following equation: TA-MAX =TJ-MAX-OP –(θJA xPD-MAX). Note 7: Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues in board design. For more information on these topics, please refer to Application Note 1187: Leadless Leadframe Package (LLP) and the PCB Layout Considerations and Power Dissipation section of this datasheet. Note 8: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical (Typ) numbers are not guaranteed, but do represent the most likely norm. Unless otherwise specified, conditions for Typ specifications are: VIN= 3.6V and TA =25 oC. Note 9: CIN,COUT, C1, and C2 : Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics Note 10: Maximum IDx=20mA Note 11: ITOT is equal to the sum of all IDx currents and the current drawn from VOUT. Current can be drawn from any combination of VOUT and ID1,ID2, and ID3 as long as the maximum current does not exceed 80mA. Note 12: For the group of the three outputs on a part the following are determined: the maximum output current in the group (MAX), the minimum output current in the group (MIN), and the average output current of the group (AVG).Two matching numbers are calculated: (MAX-AVG)/AVG and (AVG-MIN)/AVG. The largest number of the two (worst case) is considered the matching figure for the group. The matching figure for a given part is considered to be the highest matching figure. The typical specification provided is the most likely norm of the matching figure for all parts. Note 13: Headroom Voltage is defined as the amount of voltage required across the regulated current sources in order to guarantee the full amount of output current is realized. VOUT –VDx =VHR. The minimum headroom required is defined as follows: VHR(min) ≥ kHR xIDx where kHR is the headroom proportionality constant and IDx is the desired controlled diode current. The LM3570 has a kHR = 25mV/mA. For more information, please refer to the output current section of this datasheet. Note 14: The EN and PWM pins have 300k Ω internal pull-down resistors. When the part is in shutdown, the PWM pin must be tied low to ensure lowest possible shutdown current. Note 15: The output switches operate at one eighth of the oscillator frequency, fOSC=8xfSW www.national.com 4 |
类似零件编号 - LM3570 |
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类似说明 - LM3570 |
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