Datasheet

TXD
DTO
RXD
DTO
Thermal
Shutdown
FAULT
GND
UV
Lockout
V
CC
or V
IO
µP
FAULT
Input
SN65HVD255
SN65HVD256, SN65HVD257
SLLSEA2C –DECEMBER 2011–REVISED SEPTEMBER 2013 www.ti.com
Undervoltage Lockout
The supply pins have undervoltage detection that places the device in protected mode. This protects the bus
during an undervoltage event on either the V
CC
or V
RXD
supply pins.
Table 4. Undervoltage Lockout 5V Only Devices (SN65HVD255 and SN65HVD257)
V
CC
DEVICE STATE BUS OUTPUT RXD
GOOD Normal Per Device State and TXD Mirrors Bus
BAD Protected High Impedance High Impedance (3-state)
Table 5. Undervoltage Lockout 5V and V
RXD
Device (SN65HVD256)
V
CC
V
RXD
DEVICE STATE BUS OUTPUT RXD
GOOD GOOD Normal Per Device State and TXD Mirrors Bus
BAD GOOD Protected High Impedance High (Recessive)
GOOD BAD Protected Recessive High Impedance (3-state)
BAD BAD Protected High Impedance High Impedance (3-state)
APPLICATION NOTE: After an undervoltage condition is cleared and the supplies have returned to valid
levels, the device typically resumes normal operation in 300 µs.
FAULT Pin (SN65HVD257)
If one or more of the faults (TXD-Dominant Timeout, RXD dominant Timeout, Thermal Shutdown or
Undervoltage Lockout) occurs, the FAULT pin (open-drain) turns off, resulting in a high level when externally
pulled up to V
CC
or IO supply.
Figure 5. FAULT Pin Function Diagram and Application
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Product Folder Links: SN65HVD255 SN65HVD256 SN65HVD257