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LM3281 データシート(PDF) 11 Page - Texas Instruments |
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LM3281 データシート(HTML) 11 Page - Texas Instruments |
11 / 26 page LM3281 www.ti.com SNVSA38 – NOVEMBER 2014 Feature Description (continued) 7.3.3 Low IQ An ECOnomy (ECO) mode of operation draws 16 µA (typ.) quiescent current, permitting the LM3281 to be used in “always-on” applications. This low IQ is achieved over the entire input supply range of 5.5 V to 2.6 V, irrespective of whether LM3281 is operating in regulation (ECO Mode or Analog Bypass mode) or in full dropout (full bypass). 7.3.4 Forced PWM Operation ECO mode provides low IQ while PWM mode optimizes output voltage ripple and transient performance. When high, the MODE pin permits automatic mode selection based on load current. When MODE is pulled low the LM3281 enters “forced PWM” operation with very low ripple and optimized transient response. Alternately, the MODE pin can be tied high in an application to allow the device to always select a mode of operation automatically. 7.3.5 High Maximum Current Load current of 1.2 A is supported with short bursts (of < 100 µS with < 10% duty cycle) up to 1.4 A. A wide variety of load current use cases are accommodated by the LM3281. Examples are described in Table 1 and Table 2: one for high ambient temperature all the time, and one for a more typical ambient temperature use case. Many alternate use case scenarios are available; please contact TI to discuss the load current relevant for a given application. For the high ambient temperature of 85°C for the entire device operational lifetime, see Table 1: Table 1. ILOAD Example for Constant 85°C Ambient Temperature ILOAD AMBIENT TEMPERATURE PERCENT OPERATIONAL LIFETIME 100 mA 85°C Up to 100% 700 mA 85°C Up to 60% 1400 mA 85°C Up to 3% For a more typical ambient temperature distribution of TA ≤ 70°C for ≥ 80% of the operational lifetime and 70°C < TA ≤ 85% for ≤ 20% of the operational lifetime, see Table 2: Table 2. ILOAD Example for a More Typical Ambient Temperature Use ILOAD AMBIENT TEMPERATURE PERCENT OPERATIONAL LIFETIME 100 mA 70°C < TA ≤ 85°C for ≤ 20% of time Up to 100% TA ≤ 70°C for ≥ 80% of time 850 mA 70°C < TA ≤ 85°C for ≤ 20% of time Up to 60% TA ≤ 70°C for ≥ 80% of time 1400 mA 70°C < TA ≤ 85°C for ≤ 20% of time Up to 3% TA ≤ 70°C for ≥ 80% of time 7.3.6 High-Capacitance Load and Line Transient Performance The LM3281 is internally compensated to drive loads with large bypass capacitance, including transceiver modules, without sacrificing transient performance. Please reference Total Effective Output Capacitance (COUT + CLOAD1 + CLOAD2) regarding output capacitance requirements. 7.3.7 Soft Start During start-up a soft-start feature prevents high input current which could cause supply voltage bus drops and interfere with other subsystems sharing the supply bus. Soft start is especially valuable in applications where large load capacitance must be charged on start-up. Loading of the output during start-up condition will extend the soft-start time. Excessive loading may even prevent the output from reaching the target voltage, and the device may therefore stay in the soft-start condition indefinitely. Copyright © 2014, Texas Instruments Incorporated Submit Documentation Feedback 11 Product Folder Links: LM3281 |
同様の部品番号 - LM3281_15 |
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同様の説明 - LM3281_15 |
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