AN2984

2/8

Doc ID 15690 Rev 1

The RHFL4913A operates with an input supply of up to 12 V. To adjust the output voltage,

connected between the ADJ and ground. Resistor values can be derived from the following

formula:

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

above the power element saturation voltage. The ADJ 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 minimum of

should always be externally interconnected, otherwise the stability and 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 where 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 can 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. The ESR

capacitor range is from 0.01

Ω to over 20 Ω . This range is useful when ESR increases at a

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

Figure 2.

Internal block diagram