Application information

RHFL4913

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7

Application information

pins. The R1 resistor must be connected between ADJ and ground. Resistor values can be

derived from the following formula:

The minimum output voltage is therefore 1.22 V and minimum input voltage is 3 V.

above the power element saturation voltage. The adjust pin to ground resistor value must

not be greater than 10 k

Ω, in order to keep the output feedback error below 0.2%. A

reliability of the device cannot be guaranteed. The inhibit function switches off the output

current electronically, and therefore very quickly. According to Lenz’s Law, external circuitry

reacts with LdI/dt terms which can be of high amplitude in case somewhere a serial coil

inductance exists. Large transient voltage would develop on both device terminals. It is

advisable to protect the device with Schottky diodes to prevent negative voltage excursions.

In the worst case, a 14 V Zener diode could protect the device input. The device has been

designed for high stability and low dropout operation. Therefore, tantalum input and output

capacitors with a minimum 1 µF are mandatory. Capacitor ESR range is from 0.5

Ω to over

20

Ω. This range is useful when ESR increases at low temperature. When large transient

currents are expected, larger value capacitors are necessary.

In the case of high current operation with short circuit events expected, caution must be

exercised with regard to capacitors. They must be connected as close as possible to the

device terminals. As some tantalum capacitors may permanently fail when subjected to high

charge-up surge currents, it is recommended to decouple them with 470 nF polyester

capacitors.

Since the RHFL4913 adjustable voltage regulator is manufactured with very high speed

care, with very low inductance and low mutually coupling lines. Otherwise, high frequency

parasitic signals may be picked up by the device resulting in system self-oscillation. The

benefit is an SVR performance extended to far higher frequencies.

7.1

Notes on the 16-pin hermetic package

The bottom section of the 16-pin package is metallized in order to allow the user to directly

solder the RHFL4913 onto the equipment heat sink for enhanced heat removal.

7.2

Remote sensing operation

A separate kelvin voltage sensing line provides the ADJ pin with exact load "high potential"

information (see Figure 3) . But variable remote load current consumption induces variable

element) routed through the parasitic series line resistor RW2. To compensate for this