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RHFL4913 Datasheet(PDF) 8 Page - STMicroelectronics |
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RHFL4913 Datasheet(HTML) 8 Page - STMicroelectronics |
8 / 16 page Application information RHFL4913 ADJUSTABLE VERSION 8/16 5 Application information Adjusting Output Voltage: R2 resistor must be connected between VO and ADJ pins. R1 resistor must be connected between ADJ and Ground. Resistor values can be derived from the following formula: VO = VADJ (R1+ R2) / R1 VADJ is 1.23V, controlled by the internal temperature compensated Band Gap block. The minimum Output voltage is therefore 1.22V and minimum Input voltage is 3V. The RHFL4913 Adjustable is functional as soon as VI - VO voltage difference is slightly above the power element saturation voltage. The Adjust pin to Ground resistor must not be bigger than 10k Ω to keep the output feed-back error below 0.2%. A minimum 0.5mA IO must be set to ensure perfect “no-load” regulation. It is advisable to dissipate this current into the divider bridge resistor. All available VI pins shall always be externally interconnected, same thing for all available VO pins, otherwise Device stability and reliability cannot be granted. The INHIBIT function switches off the output current in an electronic way, that is very quickly. According to Lenz’s Law, external circuitry reacts with LdI/dt terms which can be of high amplitude in case somewhere an inductance exists. Large transient voltage would develop on both Device terminals. It is advisable to protect the Device with Schottky diodes preventing negative voltage excursions. In the worst case, a 14V Zener diode shall protect the Device Input. The Device has been designed for high stability and low drop out operation: Minimum 1µF input and output tantalum capacitors are therefore mandatory. Capacitor ESR range is from 0.5 Ω to over 20 Ω. Such range turns out to be useful when ESR increases at low temperature. When large transient currents are expected, larger value capacitors are necessary. In case of high current operation with expected short-circuit events, caution must be considered relatively to capacitors. They must be connected as close as possible to device terminals. As some tantalum capacitors may permanently fail when submitted to high charge-up surge currents, it is recommended to decouple them with 470nF polyester capacitors. Being RHFL4913 Adjust manufactured with very high speed bipolar technology (6GHz fT transistors), the PCB layout must be performed with exceptional care, very low inductance, low mutually coupling lines, otherwise high frequency parasitic signals may be picked-up by the Device resulting into system self- oscillation. The benefit is an SVR performance extended to far higher frequencies. 5.1 Notes about 16pin hermetic package The bottom section of 16pin packages is metallized in order to allow User to directly solder the RHFL4913A on the equipment heat sink for enhanced heat removal. 5.2 Remote sensing operation See Figure 2. A separate Kelvin Voltage sensing line provides ADJ pin with exact Load "high potential" information. But variable remote Load current consumption induces variable Iq current (Iq is roughly the IO current divided by the hFE of the internal PNP series power element) routed through parasitic series line resistor symbolized as RW2. To compensate this parasitic voltage, the Resistor RW1 introduced on purpose provides the necessary compensating voltage signal to ADJust pin. |
Similar Part No. - RHFL4913_07 |
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Similar Description - RHFL4913_07 |
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