RHFL4913 FIXED VERSION

6/11

Alternate to

RHFL4913 Fixed (& custom) Voltages replace all 3-terminal Industry Devices, providing essential benefits

- Lower Drop-Out

- High radiation performance

-BetterSVR

- Saving the high stability external setting resistors.

APPLICATION INFORMATION

otherwise Device stability and reliability cannot be granted. All NC pins can be connected to Ground. 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 some

series-inductance exists. The effect would be a large transient voltage developed on both Device

terminals. It is necessary 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.

transistors), the PCB lay-out must be performed with extreme care, very low inductance, low mutually

coupling lines, otherwise high frequency parasitic signals may be picked-up by the Device resulting into

self-oscillation. User’s benefit is a SVR performance extended to far higher frequencies.

REMOTE SENSING OPERATION

In case the Load is located far from the regulator, it is recommended to comply with the scheme below. To

obtain the best regulation, it is in addition essential to care about:

- The wire connecting R2 to the Load end must not be crossed by the Load current (Kelvin sense).

The noise captured by the wires between the Load and the chip could bring a noisy output voltage. In case

this happens, it is recommended that shielded cables are used for these connections. The external wrap

must be used for connecting the ground of the chip with the Load Ground. It is also recommended to place

1uF tantalum capacitors between Output and Ground close to the device and another next to the Load.