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LM26001Q 数据表(PDF) 11 Page - Texas Instruments |
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LM26001Q 数据表(HTML) 11 Page - Texas Instruments |
11 / 28 page Vout 10 mV/Div VSW 5V/Div IL 200 mA/Div 1 Ps/DIV 0 10 20 30 40 VIN (V) 0 50 100 150 200 250 22 PH 15PH 22PH 15PH 500 kHz 330 kHz LM26001, LM26001Q www.ti.com SNVS430F – MAY 2006 – REVISED NOVEMBER 2010 Figure 17. Sleep Mode Threshold vs Vin Vout = 3.3V Below the sleep threshold, decreasing load current results in longer sleep cycles, which can be quantified as shown below: Dwake = Iload/Isleep (2) Where Dwake is the percentage of time awake when the load current is below the sleep threshold. Sleep mode combined with low IQ operation minimizes the input supply current. Input supply current in sleep mode can be calculated based on the wake duty cycle, as shown below: Iin = Iq + (IQG x Dwake) + (Io x D) (3) Where IQG is the gate drive current, calculated as: IQG = (4.6 x 10 -9) x f SW And Io is the sum of Iload, Ibias, and current through the feedback resistors. Because this calculation applies only to sleep mode, use the Iq_Sleep_VB and IBIAS_SLEEP values from the Electrical Characteristics. If VBIAS is connected to ground, use the same equation with Ibias equal to zero and Iq_Sleep_VDD. FPWM Pulling the FPWM pin high disables sleep mode and forces the LM26001 to always operate in PWM mode. Light load efficiency is reduced in PWM mode, but switching frequency remains stable. The FPWM pin can be connected to the VDD pin to pull it high. In FPWM mode, under light load conditions, the regulator operates in discontinuous conduction mode (DCM) . In discontinuous conduction mode, current through the inductor starts at zero and ramps up to its peak, then ramps down to zero again. Until the next cycle, the inductor current remains at zero. At nominal load currents, in FPWM mode, the device operates in continuous conduction mode, where positive current always flows in the inductor. Typical discontinuous operation waveforms are shown in Figure 18. Figure 18. Discontinuous Mode Waveforms 75mA Load, Vin = 12V At very light load, in FPWM mode, the LM26001 may enter sleep mode. This is to prevent an over-voltage condition from occurring. However, the FPWM sleep threshold is much lower than in normal operation. Copyright © 2006–2010, Texas Instruments Incorporated Submit Documentation Feedback 11 Product Folder Links: LM26001 LM26001Q |
类似零件编号 - LM26001Q |
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类似说明 - LM26001Q |
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