si8405 Silicon Laboratories, si8405 Datasheet - Page 15

• Manufacturer Part Number: si8405
• Description: Bidirectional I 2c Isolators With Unidirectional Digital Channels
• Manufacturer: Silicon Laboratories

3. Device Operation
Device behavior during start-up, normal operation, and shutdown is shown in Figure 12, where UVLO+ and UVLO-
are the positive-going and negative-going thresholds respectively. Refer to Table 11 to determine outputs when
power supply (VDD) is not present.
3.1. Device Startup
Outputs are held low during powerup until VDD is above the UVLO threshold for time period tSTART. Following
this, the outputs follow the states of inputs.
3.2. Under Voltage Lockout
Under Voltage Lockout (UVLO) is provided to prevent erroneous operation during device startup and shutdown or
when VDD is below its specified operating circuits range. Both Side A and Side B each have their own under
voltage lockout monitors. The Si840x Side A enters UVLO when AVDD < V
AVDDUV+. Side B operates the same as Side A with respect to its BVDD supply. Each side can enter or exit UVLO
independently. For example, Side A unconditionally enters UVLO when AVDD falls below AVDDUV– and exits
UVLO when AVDDA rises above AVDD
BVDD
INPUT
OUTPUT
AVDD
UVLO+
UVLO-
UVLO+
UVLO-
tSTART
Figure 12. Device Behavior during Normal Operation
tSD
tSTART
UV+
.
Preliminary Rev. 0.1
tSTART
AUVH
–, and exits UVLO when AVDD >
tPHL
tPLH
Si840x
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