It features a wide supply range of 4. The output voltage is set to 3. A KHz high switching frequency allows the use of small, low cost capacitors and inductors. Fault condition protection includes cycle-by-cycle current limiting, thermal shutdown, and under-voltage lockout. Internal soft-start reduces the turn-on stress. The small but thermally enhanced 8-pin SOIC package minimizes board area and provides excellent thermal management.

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It achieves 3A of continuous output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown.

An adjustable soft-start reduces the stress on the input source at startup. In shutdown mode the regulator draws 20? A of supply current. The MP requires a minimum number of readily available external components, providing a compact solution. Programmable Soft-Start? A Shutdown Mode? Fixed KHz Frequency?

Thermal Shutdown? Cycle-by-Cycle Over Current Protection? Wide 4. Output Adjustable from 1. Under-Voltage Lockout?

Distributed Power Systems? Battery Chargers? Pre-Regulator for Linear Regulators? Flat Panel TVs? Set-Top Boxes? Cigarette Lighter Powered Devices? Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. VSW — 0. Power Input. IN supplies power to the IC. Drive IN with a 4. See Input Capacitor.

Power Switching Output. SW is the switching node that supplies power to the output. Note that a capacitor is required from SW to BS to power the high-side switch.

Note: Connect the exposed pad to Pin 4. Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive voltage 5 FB divider from the output voltage to ground.

The feedback threshold is 1. See Setting the Output Voltage. Compensation Node. COMP is used to compensate the regulation control loop. See Compensation. Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the 7 EN regulator; low to turn it off. For complete low current shutdown the EN pin voltage needs to be less than 0. For automatic startup leave EN disconnected. Soft-Start Control Input. SS controls the soft-start period.

F capacitor sets the soft-start period to 10ms. To disable the soft-start feature, leave SS disconnected. MP Rev. It regulates input voltages from 4. The MP uses current-mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal error amplifier. The output current of the transconductance error amplifier is presented at COMP where a network compensates the regulation control system.

The voltage at COMP is compared to the internally measured switch current to control the output voltage. The capacitor is internally charged when SW is low.

An internal 10? For a 3. Inductor The inductor is required to supply constant current to the output load while being driven by the switched input voltage. A larger value inductor will result in less ripple current that will result in lower output ripple voltage. Also, make sure that the peak inductor current is below the maximum switch current limit. Where VIN is the input voltage, fS is the switching frequency and?

IL is the peak-to-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current. Table 1 lists a number of suitable inductors from various manufacturers. The choice of which inductor to use mainly depends on the price vs.

Use a Schottky diode to reduce losses due to diode forward voltage and recovery times. Choose a diode whose maximum reverse voltage rating is greater than the maximum input voltage, and whose current rating is greater than the maximum load current.

Table 2 lists example Schottky diodes and manufacturers. Use low ESR capacitors for the best performance. Ceramic capacitors are preferred, but tantalum or low-ESR electrolytic capacitors will also suffice.

Since the input capacitor C1 absorbs the input switching current it requires an adequate ripple current rating. The input capacitor can be electrolytic, tantalum or ceramic. When using electrolytic or tantalum capacitors, a small, high quality ceramic capacitor i. F should be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at the input.

The input voltage ripple caused by the capacitance can be estimated by:? Output Capacitor The output capacitor is required to maintain the DC output voltage. Ceramic, tantalum or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by:? In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance, which is the main cause of the output voltage ripple.

For simplification, the output voltage ripple can be estimated by:? In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to:? The system stability and transient response are controlled through the COMP pin.

COMP is the output of the internal transconductance error amplifier. A series capacitor-resistor combination sets a pole-zero combination to control the characteristics of the control system. The system has two poles of importance.

One is due to the compensation capacitor C3 and the output resistor of error amplifier, while the other is due to the output capacitor and the load resistor. The system has one zero of importance, due to the compensation capacitor C3 and the compensation resistor R3. The system crossover frequency where the feedback loop has unity gain is important.

Lower crossover frequencies result in slower line and load transient responses, while higher crossover frequencies could cause system instability. A good standard is to set the crossover frequency to approximately one-tenth of the switching frequency. Table 3 lists the typical values of compensation components for some standard output voltages with various output capacitors and inductors.

The values of the compensation components have been optimized for fast transient responses and good stability at given conditions. H ? H C2 ? F Ceramic 47?





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Monolithic Power Systems MP1593DN-LF-Z



Monolithic Power Systems MP1593DN-LF-Z


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