ZHCSL04A March 2020 – July 2020 ISO1044
PRODUCTION DATA
The supply pins have undervoltage detection that places the device in protected or default mode which protects the bus during an undervoltage event on the VCC1 or VCC2 supply pins. If the bus-side power supply, VCC2, is less than about 4 V, the power shutdown circuits in the ISO1044B device disable the transceiver to prevent false transmissions because of an unstable supply. If the VCC1 supply is still active when this occurs, the receiver output (RXD) goes to a default HIGH (recessive) value. Table 8-1 summarizes the undervoltage lockout and fail-safe behavior.
| VCC1 | VCC2 | DEVICE STATE | BUS OUTPUT | RXD |
|---|---|---|---|---|
| > UVVCC1 | > UVVCC2 | Functional | Per Device State and TXD | Mirrors Bus |
| <UVVCC1 | > UVVCC2 | Protected | Recessive | Undetermined |
| >UVVCC1 | < UVVCC2 | Protected | High Impedance | Recessive (Default High) |
After an undervoltage condition is cleared and the supplies have returned to valid levels, the device typically resumes normal operation in 300 µs.