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LMR22007YYZFR Datasheet(PDF) 11 Page - Texas Instruments |
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LMR22007YYZFR Datasheet(HTML) 11 Page - Texas Instruments |
11 / 24 page IN OUT ON LPSM(peak) (V V ) t i L K OUT ON IN V t 478ns V K 0 0 VIN -VD1 t t D = tON / TSW ttONt ttOFFt VSW iL tTSWt IOUT ILPK tûiLt LMR22007 www.ti.com SNVS985A – OCTOBER 2013 – REVISED OCTOBER 2013 The LMR22007 synchronous switched mode power converters are based on DCS-Control™ (Direct Control with Seamless Transition into Power Save Mode), an advanced regulation topology, that combines the advantages of hysteretic, voltage mode and current mode control including an AC loop directly associated to the output voltage. This control loop takes information about output voltage changes and feeds it directly to a fast comparator stage. It sets the switching frequency, which is constant for steady state operating conditions, and provides immediate response to dynamic load changes. To get accurate DC load regulation, a voltage feedback loop is used. The internally compensated regulation network achieves fast and stable operation with small external components and low ESR capacitors. The DCS-Control™ topology supports PWM (Pulse Width Modulation) mode for medium and heavy load conditions and a Power Save Mode at light loads. During PWM, it operates at its nominal switching frequency in continuous conduction mode. This frequency is typically about 2.1 MHz with a controlled frequency variation depending on the input voltage. If the load current decreases, the converter enters Power Save Mode to sustain high efficiency down to very light loads. In Power Save Mode the switching frequency decreases linearly with the load current. Since DCS-Control™ supports both operation modes within one single building block, the transition from PWM to Power Save Mode is seamless without effects on the output voltage. Detailed Description of Pins and Key Functions POWER SAVE MODE OPERATION The LMR22007's built in Power Save Mode will be entered seamlessly, if the load current decreases. This secures a high efficiency in light load operation. The device remains in Power Save Mode as long as the inductor current is discontinuous. In Power Save Mode the switching frequency decreases linearly with the load current maintaining high efficiency. The transition into and out of Power Save Mode happens within the entire regulation scheme and is seamless in both directions. The LMR22007 includes a fixed on-time circuitry. This on-time, in steady-state operation, can be estimated as: (1) For very small output voltages, an absolute minimum on-time of about 77ns is kept to limit switching losses. Using tON, the typical peak inductor current in Power Save Mode can be approximated by: (2) When VIN decreases to typically 15% above VOUT, the LMR22007 won't enter Power Save Mode, regardless of the load current. The device maintains output regulation in PWM mode. ENABLE (EN) The simplest way to enable the operation of the LMR22007 is to connect the EN pin to VIN which allows self start-up of the LMR22007 when the input voltage is applied. A resistor value of less than 3k Ω is recomended. Copyright © 2013, Texas Instruments Incorporated Submit Documentation Feedback 11 Product Folder Links: LMR22007 |
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