SI82390AD-IS Datasheet, PDF (11/38 Pages) Silicon Laboratories – 4.0 A ISODrivers with 2.5 V VDDI and Safety Features

Si8239x Data Sheet
System Overview
2.6.2 Undervoltage Lockout
Undervoltage Lockout (UVLO) is provided to prevent erroneous operation during device startup and shutdown or when VDD is below its
specified operating circuits range. The input (control) side, Driver A and Driver B, each have their own undervoltage lockout monitors.
The Si8239x input side enters UVLO when VDDI < VDDIUV–, and exits UVLO when VDDI > VDDIUV+. The driver outputs, VOA and
VOB, remain low when the input side of the Si8239x is in UVLO and their respective VDD supply (VDDA, VDDB) is within tolerance.
Each driver output can enter or exit UVLO independently for the Si82394/5/6/7/8 products. For example, VOA unconditionally enters
UVLO when VDDA falls below VDDAUV– and exits UVLO when VDDA rises above VDDAUV+. For the Si82390/1 products, when ei-
ther VDDA or VDDB falls under VDDxUV–, this information is fed back through the isolation barrier to the input side logic which forces
VOB or VOA to be driven low respectively under these conditions. If the application is driving a transformer for an isolated power con-
verter, for example, this behavior is useful to prevent flux imbalances in the transformer. Please note that this feature implies that it can
only be implemented when the VDDA and VDDB power supplies are independent from each other. If a bootstrap circuit is used for
Si82390/1, it will prevent the IC from powering up. Please do not use the Si82390/1 in conjunction with a bootstrap circuit for driver
power.
Figure 2.16. Si82391/6/8 Device Behavior during Normal Operation and Shutdown
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