Application information

RHFL7913A

10/19

6

Application information

resistor must be connected between ADJ and GND pins. Resistor values can be derived

from the following formula:

To access all RHFL7913A adjustable functionality, V (+) shall be set at 3.0 V (max 5 V). As a

operation rating.

element saturation voltage. The adjustable pin to Ground resistor shall not be greater than

10 k

set to ensure perfect “no-load” regulation. It can be wise to dissipate this current into the

divider bridge resistor.

otherwise device stability and reliability cannot be granted. The INHIBIT function switches

off output current in an electronic way, is very quickly. According to Lenz’ Law, external

circuitry reacts with –LdI/dt terms which can be of high amplitude in case some series-

inductance exists. Effect would be large transient voltage developed on both device

beyond max ratings. In the worst case, a 14 V Zener diode shall protect the device input. In

The device has been designed for high stability and low drop out operation: minimum 1 µF

input and output tantalum capacitors are therefore mandatory. Typical industry PCB design

practices 10 µF capacitors values are acceptable. Capacitor ESR range is from 0.020

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 shall be

considered relatively to capacitors. They shall be connected as close as possible form

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

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

ceramic capacitors.

RHFL7913A adjustable being manufactured with very high speed bipolar technology (6 GHz

inductance, low mutually coupling lines, otherwise high frequency parasitic signals may be

picked-up by the Device resulting into system self-oscillation. In difficult high current

circumstances (coming from PCB layout) a 470 nF polyester capacitor connected between

higher frequencies.