Datasheet

Functional description L5980
8/42 Doc ID 13003 Rev 6
4 Functional description
The L5980 is based on a “voltage mode”, constant frequency control. The output voltage
V
OUT
is sensed by the feedback pin (FB) compared to an internal reference (0.6 V) providing
an error signal that, compared to a fixed frequency sawtooth, controls the on and off time of
the power switch.
The main internal blocks are shown in the block diagram in Figure 3. They are:
● A fully integrated oscillator that provides sawtooth to modulate the duty cycle and the
synchronization signal. Its switching frequency can be adjusted by and external
resistor. The voltage and frequency feed forward are implemented.
● The soft-start circuitry to limit inrush current during the start up phase.
● The voltage mode error amplifier
● The pulse width modulator and the relative logic circuitry necessary to drive the internal
power switch.
● The high-side driver for embedded p-channel power MOSFET switch.
● The peak current limit sensing block, to handle overload and short circuit conditions.
● A voltage regulator and internal reference. It supplies internal circuitry and provides a
fixed internal reference.
● A voltage monitor circuitry (UVLO) that checks the input and internal voltages.
● A thermal shutdown block, to prevent thermal run away.
Figure 3. Block diagram