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4.1

Power supply and voltage reference

The internal regulator circuit (shown in Figure 2) consists of a start-up circuit, an internal

voltage preregulator, the bandgap voltage reference and the bias block that provides current

to all the blocks.

The starter gives the start-up currents to the whole device when the input voltage goes high

and the device is enabled (inhibit pin connected to ground).

a very low supply voltage noise sensitivity.

4.2

Voltages monitor

Figure 3.

Internal regulator circuit

4.3

Oscillator and synchronizator

Figure 4 shows the block diagram of the oscillator circuit.

The clock generator provides the switching frequency of the device that is internally fixed at

500 kHz. The frequency shifter block acts reducing the switching frequency in case of strong

overcurrent or short circuit. The clock signal is then used in the internal logic circuitry and is

the input of the ramp generator and Synchronizator blocks.

The ramp generator circuit provides the sawtooth signal, used to realize the PWM control

and the internal voltage feed forward, while the synchronizator circuit generates the

synchronization signal. Infact the device has a synchronization pin that can works both as

master and slave.

As master to synchronize external devices to the internal switching frequency.