8

Device description

The RHFL6000L adjustable voltage regulator contains a PNP type power element controlled by a signal resulting

from an amplified comparison between the temperature-compensated internal bandgap and the fraction of the

desired output voltage value obtained from an external resistor divider bridge, for VO ≥ 1.25 V.

For VO < 1.25 V, the external resistor divider is moved upstream to the error amplifier and therefore the

comparison occurs between a fraction of the temperature-compensated internal bandgap (according to the

desired output voltage value) and the output voltage itself. The device is protected by several functional blocks.

8.1

ADJ pin

The feedback voltage necessary for the loop regulation comes from the load through an external resistor divider

(R1, R2 as in Figure 5. Typical application diagram for Vout < 1.25 V) whose midpoint is connected to the ADJ/

SENSE pin, allowing all possible output voltage settings for VOUT > 1.25 V as per user requirements.

8.2

Inhibit ON-OFF control

By setting the INHIBIT pin to TTL high level, the device switches off. The device is in ON-state when the INHIBIT

pin is set low. Since the INHIBIT pin is pulled down internally, it can be left floating whenever the inhibit function is

not used. Alternatively, it can also be shorted to the GND.

8.3

Overtemperature protection

A temperature detector internally monitors the power element junction temperature. The device turns off when a

temperature of approximately 175 °C is reached, returning to ON mode when the temperature decreases down to

approximately 135 °C.

It should be noted that when the internal temperature detector reaches 175 °C, the active power element can be

as high as 225 °C. Prolonged operation under these conditions may exceed the maximum operating ratings and

device reliability cannot be guaranteed.

8.4

Overcurrent protection

A default internal constant current limit is set at ISHORT = 3 A (when VO is at 0 V).

This value can be decreased via an external resistor (RSHORT) connected between the ISC and VI pins, with a

typical value range of 10 kΩ to 200 kΩ.

To maintain optimal regulation, it is necessary to set ISHORT 1.6 times greater than the desired maximum

operating current (IO ). When IO reaches ISHORT–300 mA, the current limiter intervenes, VO starts to drop and the

OCM flag is raised. When no current limitation adjustment is required, the ISC pin must be left unbiased.

The combination of overcurrent and overtemperature circuits provides the RHFL6000L with a high level of

protection against destructive junction temperature excursions in all load conditions.

8.5

OCM pin

The OCM pin is an open collector flag normally pulled up at VI by a 5 kΩ resistor.

It goes to low state when the current limit becomes active. It is buffered and can sink 10 mA.

8.6

STAB pin

The STAB pin gives the user direct access to regulator internal control loop stability adjustment. Its usage is

optional and it should be left unconnected when not used.

8.7

FILT C pin

The FILT_C pin helps limiting SET amplitudes and output noise when bypassed vs. GND through a 22 µF

polyester capacitor, Cfilt. Its usage is therefore mandatory in both SET and low-noise applications. Out of the

mentioned cases, Cfilt is not needed.

RHFL6000L

Device description

DS14125 - Rev 1

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