Use the  open-drain logic to run at 1.8V at the 1-Wire master IO. Most 1-Wire slave devices cannot run at 1.8V. Here, the application  presents an RD (reference design) of a circuit that translates from a 1.8V 1-Wire master to a 5V 1-Wire slave device. The Reference Design  is used for driving typical 1-Wire slave devices. In this design the MAX3394E voltage-level translator is featured.

Devices such as FPGAs, microprocessors, the DS2482-100, and DS2480B are examples of 1-Wire master devices. The 1-Wire/iButton® slave devices are manufactured by Maxim and comprise an extensive family of parts that typically operate from 2.8V to 5.25V. The 1-Wire masters and slave devices have traditionally been 5V open-drain logic in the past.

Today designers need open-drain logic to run at 1.8V at the 1-Wire master IO. While most 1-Wire slave devices can run safely at 5V, most of those same devices cannot run at 1.8V. A bidirectional voltage-level translator circuit is needed to overcome this limitation. This RD (reference design) features the Maxim® MAX3394E, which is a bidirectional voltage-level translator for these applications.

The MAX3394E is a dual-level translator available in an 8-pin, 3mm x 3mm TDFN package. It is ideal for driving high-capacitive loads, thanks to its internal slew-rate enhancement circuitry. 1-Wire slave devices often have capacitive loading greater than 500pF. The MAX3394E's VCC I/O pins are protected to ±15kV HBM (Human Body Model), which protects the 1-Wire master. The 1-Wire bus architectures often interface to the external world, making HBM essential. However, it is recommended that a DS9503P be added as ESD protection for the pullup resistor (R3), the optional strong pullup circuitry, and the 1-Wire slave device.

This RD for 1.8V to 5V 1-Wire bidirectional logic-level translation drives typical 1-Wire slave devices. The design was built and then tested.

Reference Design of a 1-Wire® Bidirectional Voltage-Level Translator for 1.8V to 5V