Rainbow-electronics MAX1844 Bedienungsanleitung

General DescriptionThe MAX1844 pulse-width modulation (PWM) controllerprovides high efficiency, excellent transient response,and high DC output accura

Detailed DescriptionThe MAX1844 buck controller is targeted for low-voltagepower supplies for notebook computers. Maxim’s propri-etary Quick-PWM pulse

battery supply, the enable signal (SHDN) must bedelayed until the battery voltage is present in order toensure startup. The 5V bias supply provides VC

MAX1844width is inversely proportional to input voltage and directlyproportional to output voltage. Another one-shot sets aminimum off-time (400ns typ

where VDROP1is the sum of the parasitic voltage dropsin the inductor discharge path, including synchronousrectifier, inductor, and PC board resistance

MAX1844Current-Limit Circuit (ILIM)The current-limit circuit employs a unique “valley” cur-rent-sensing algorithm (Figure 4). If the magnitude of thec

Power-Good Output (PGOOD)The PGOOD window comparator continuously monitorsthe output. PGOOD is actively held low in shutdown,standby, and soft-start.

MAX1844Fixed Output VoltagesThe MAX1844’s Dual ModeTMoperation allows the selec-tion of common voltages without requiring external com-ponents (Figure

The amount of output sag is also a function of the maxi-mum duty factor, which can be calculated from the on-time and minimum off-time: where and mini

MAX1844Output Capacitor Stability ConsiderationsStability is determined by the value of the ESR zero rela-tive to the switching frequency. The point o

pation limits often limits how small the MOSFET can be.Again, the optimum occurs when the switching (AC)losses equal the conduction (RDS(ON)) losses.

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Therefore, VINmust be greater than 3.13V, even withvery large output capacitance, and a practical input volt-age with reasonable output capacitance wo

32L QFN .EPSMAX1844High-Speed Step-Down Controller withAccurate Current Limit for Notebook Computers22 _______________________________________________

MAX1844High-Speed Step-Down Controller withAccurate Current Limit for Notebook ComputersMaxim cannot assume responsibility for use of any circuitry ot

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Standard Application CircuitThe standard application circuit (Figure 1) generates a2.5V rail for general-purpose use in a notebook computer.See Table