A5973AD_0808 Datasheet, PDF (8/19 Pages) STMicroelectronics – Up to 1.5 A step down switching regulator for automotive applications

A5973AD
Functional description
4.1
Power supply and voltage reference
The internal regulator circuit (shown in Figure 4) 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).
The preregulator block supplies the bandgap cell with a preregulated voltage V_REG that has
a very low supply voltage noise sensitivity.
4.2
Voltages monitor
An internal block senses continuously the VCC, VREF and VBG. If the voltages go higher than
their thresholds, the regulator starts to work. There is also an hysteresis on the VCC (UVLO).
Figure 4. Internal regulator circuit
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