Reference Circuit 4477

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



Introduction

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.

Voltage-Level Translator

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.

Application Circuit

The circuit in Figure 1 shows the MAX3394E used to perform bidirectional 1.8V to 5V voltage-level translation in an open-drain system.

Figure 1. Schematic of 1-Wire bidirectional voltage level translation from 1.8V to 5V. Note that the pins I/O VL and I/O VCC have a typical 10kΩ internal pullup. The BOM (bill of materials) for this reference design is given in Table 1.

Introduction

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.

Voltage-Level Translator

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.

Application Circuit

The circuit in Figure 1 shows the MAX3394E used to perform bidirectional 1.8V to 5V voltage-level translation in an open-drain system.

Figure 1. Schematic of 1-Wire bidirectional voltage level translation from 1.8V to 5V. Note that the pins I/O VL and I/O VCC have a typical 10kΩ internal pullup. The BOM (bill of materials) for this reference design is given in Table 1.

Table 1. Bill of Materials
Item Quantity Reference Part Manufacturer Part Number
1 1 C1 1.0µF 0402 Panasonic ECJ-0EB0J105M
2 2 C2, C3 0.1µF 0201 Panasonic ECJ-ZEB0J104K
3 1 Q1 BSS84-7-F Diodes, Inc/Zetex BSS84-7-F
4 1 R1 33Ω 0201 Panasonic ERJ-1GEJ330C
5 1 R2 10kΩ 0402 Panasonic ERJ-2RKF1002X
6 1 R3 1kΩ 0402 Panasonic ERJ-2RKF1001X
7 1 R4 2.2kΩ 0402 Panasonic ERJ-2RKF2201X
8 2 CH1, CH2 TEST POINT N/A N/A
9 1 U1 MAX3394E Maxim MAX3394EETA+

Waveform Measurements/Test Results

The test results in Figures 2 through 5 were generated from the board built for evaluating the circuit. Setup:

  • VL = 1.8V
  • VCC = 5.0V
  • CH1: 1-Wire master (OW_MASTER)
  • CH2: DS1920 (OW_SLAVE)
  • OW_SLAVE wire length: 2.4m, max.
  • Test results did not include the optional strong pullup circuitry in Figure 1.
  • Room temperature measurements only

Figure 2. The scope plot of a 1-Wire Reset shows the performance of the MAX3394E with presence pulse amplitude of no more than 250mV, lower than a typical 1-Wire master VIL maximum of 0.4V.
Figure 2. The scope plot of a 1-Wire Reset shows the performance of the MAX3394E with presence pulse amplitude of no more than 250mV, lower than a typical 1-Wire master VIL maximum of 0.4V.

Figure 3. The scope plot of a 1-Wire Write, one timeslot with a clean tLOW1 < 15µs.

Figure 4. The scope plot of a 1-Wire Write, zero timeslot with 60µs < tLOW0 < 120µs.
Figure 5. The scope plot of a 1-Wire Read, zero timeslot with an active 1-Wire slave open-drain return and lower than a typical 1-Wire master VIL maximum of 0.4V.
Figure 5. The scope plot of a 1-Wire Read, zero timeslot with an active 1-Wire slave open-drain return and lower than a typical 1-Wire master VIL maximum of 0.4V.

Conclusion

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. The circuit schematic, BOM, and typical waveforms have been presented.

Resources

MAX31820PAR
1-Wire Parasite-Power, Ambient Temperature Sensor

  • Unique 1-Wire Interface Requires Only One Port Pin for Communication
  • Derives Power from Data Line (Parasite Power); No Local Power Supply Needed
  • Multidrop Capability Simplifies Distributed Temperature-Sensing Applications

MAX31820
1-Wire Ambient Temperature Sensor

  • Unique 1-Wire Interface Requires Only One Port Pin for Communication
  • Each Device has a Unique 64-Bit Serial Code Stored in On-Board ROM
  • Multidrop Capability Simplifies Distributed Temperature-Sensing Applications

MAX31826
1-Wire Digital Temperature Sensor with 1Kb Lockable EEPROM

  • Unique 1-Wire Interface Requires Only One Port Pin for Communication
  • Integrated Temperature Sensor and EEPROM Reduce Component Count
  • Multidrop Capability Simplifies Multisensor Systems

DS1922E
iButton High-Temperature Logger with 8KB Data-Log Memory

  • High Accuracy, Full-Featured Digital Temperature Logger Simplifies Temperature Data Collection and Dissemination of Electronic Temperature Record
  • Rugged Construction Survives Harsh Environments
  • Simple Serial Port Interfaces to Most Microcontrollers for Rapid Data Transfer

DS28EC20
20Kb 1-Wire EEPROM

  • 20480 Bits of Nonvolatile (NV) EEPROM Partitioned into Eighty 256-Bit Pages
  • Individual 8-Page Groups of Memory Pages (Blocks) can be Permanently Write Protected or Put in OTP EPROM-Emulation Mode ("Write to 0")
  • Read and Write Access Highly Backward-Compatible to Legacy Devices (e.g., DS2433)

DS28EA00
1-Wire Digital Thermometer with Sequence Detect and PIO

  • Digital Thermometer Measures Temperatures from -40°C to +85°C
  • Thermometer Resolution is User-Selectable from 9 to 12 Bits
  • Unique 1-Wire Interface Requires Only One Port Pin for Communication

DS1972
iButton 1024-Bit EEPROM

  • 1024 Bits of EEPROM Memory Partitioned into Four Pages of 256 Bits
  • Individual Memory Pages can be Permanently Write Protected or Put in EPROM-Emulation Mode ("Write to 0")
  • Switchpoint Hysteresis and Filtering to Optimize Performance in the Presence of Noise

MAX3394E
±15kV ESD-Protected, High-Drive Current, Dual-/Quad-/Octal-Level Translators with Speed-Up Circuitry

  • ±15kV ESD Protection on I/O VCC_ Lines
  • Bidirectional Level Translation Without Direction Pin
  • I/O VL_ and I/O VCC_ 10mA Sink-/15mA Source-Current Capability

DS28E01-100
1Kb Protected 1-Wire EEPROM with SHA-1 Engine

  • 1024 Bits of EEPROM Memory Partitioned Into Four Pages of 256 Bits
  • On-Chip 512-Bit SHA-1 Engine to Compute 160-Bit Message Authentication Codes (MAC) and to Generate Secrets
  • Write Access Requires Knowledge of the Secret and the Capability of Computing and Transmitting a 160-Bit MAC as Authorization

DS28E04-100
4096-Bit Addressable 1-Wire EEPROM with PIO

  • 4096 bits of EEPROM Memory Partitioned into 16 Pages of 256 Bits
  • Seven Address Inputs for Physical Location Configuration
  • Two General-Purpose PIO Pins with Pulse-Generation Capability

DS1923
iButton Hygrochron Temperature/Humidity Logger with 8KB Data-Log Memory

  • High Accuracy, Full-Featured Digital Temperature and Humidity Logger Simplifies Temperature Data Collection and Dissemination of Electronic Temperature Record
  • Rugged Construction Survives Harsh Environments
  • Simple Serial Port Interfaces to Most Microcontrollers for Rapid Data Transfer

DS2431
1024-Bit 1-Wire EEPROM

  • Easily Add Traceability and Relevant Information to Any Individual System
  • Minimalist 1-Wire Interface Lowers Cost and Interface Complexity

DS1922L
iButton Temperature Loggers with 8KB Data-Log Memory

  • High Accuracy, Full-Featured Digital Temperature Logger Simplifies Temperature Data Collection and Dissemination of Electronic Temperature Record
  • Rugged Construction Survives Harsh Environments
  • Simple Serial Port Interfaces to Most Microcontrollers for Rapid Data Transfer

DS1922T
iButton Temperature Loggers with 8KB Data-Log Memory

  • High Accuracy, Full-Featured Digital Temperature Logger Simplifies Temperature Data Collection and Dissemination of Electronic Temperature Record
  • Rugged Construction Survives Harsh Environments
  • Simple Serial Port Interfaces to Most Microcontrollers for Rapid Data Transfer

DS1977
iButton 32KB EEPROM

SPECIAL FEATURES
  • 32KB EEPROM Organized as Pages of 64 Bytes Each
  • Optional Password Protection with Different 64-Bit Passwords for Read and Full Access
  • Communicates to Host with a Single Digital Signal at Up to 15.3kbps at Standard Speed or Up to 125kbps in Overdrive Mode Using 1-Wire Protocol
COMMON iButton FEATURES
  • Unique Factory-Lasered 64-Bit Registration Number Assures Error-Free Device Selection and Absolute Traceability Because No Two Parts are Alike
  • Built-In Multidrop Controller for 1-Wire Net
  • Chip-Based Data Carrier Stores Digital Identification and Information, Armored in a Durable Stainless-Steel Case

DS1921G
Thermochron iButton Device

  • High Accuracy, Full-Featured Digital Temperature Logger Simplifies Temperature Data Collection and Dissemination of Electronic Temperature Record
  • Rugged Construction Survives Harsh Environments
  • Simple Serial Port Interfaces to Most Microcontrollers for Rapid Data Transfer

DS18S20
1-Wire Parasite-Power Digital Thermometer

  • Unique 1-Wire® Interface Requires Only One Port Pin for Communication
  • Maximize System Accuracy in Broad Range of Thermal Management Applications
  • Parasite Power Mode Requires Only 2 Pins for Operation (DQ and GND)

DS1961S
iButton 1Kb EEPROM with SHA-1 Engine

  • 1128 bits of 5V EEPROM memory partitioned into four pages of 256 bits, a 64-bit write-only secret and up to five general purpose read/write registers
  • Write access requires knowledge of the secret and the capability of computing and transmitting a 160-bit MAC as authorization
  • Secret and data memory can be write-protected (all or page 0 only) or put in EPROM-emulation mode ("write to 0", page 1)
Common iButton Features
  • Unique, factory-lasered and tested 64-bit registration number (8-bit family code + 48-bit serial number + 8-bit CRC tester) assures absolute traceability because no two parts are alike
  • Multidrop controller for 1-Wire net
  • Digital identification and information by momentary contact

DS1822
Econo 1-Wire Digital Thermometer

  • Unique 1-Wire® Interface Requires Only One Port Pin for Communications
  • Reduced Component Count with Integrated Temperature Sensor and Interface
  • Simplifies Distributed Temperature Sensing with Multidrop Capability

DS1921H
High-Resolution Thermochron iButton Devices

  • Digital thermometer measures temperature 1/8°C increments with ±1°C accuracy
  • Built-in real-time clock (RTC) and timer has accuracy of ±2 minutes per month from 0°C to 45°C
  • Water resistant or waterproof if placed inside DS9107 iButton capsule (Exceeds Water Resistant 3 ATM requirements)
Common iButton Features
  • Digital identification and information by momentary contact
  • Unique, factory-lasered and tested 64-bit registration number (8-bit family code + 48-bit serial number + 8-bit CRC tester) assures absolute traceability because no two parts are alike
  • Multidrop controller for 1-Wire net

DS1921Z
High-Resolution Thermochron iButton Devices

  • Digital thermometer measures temperature 1/8°C increments with ±1°C accuracy
  • Built-in real-time clock (RTC) and timer has accuracy of ±2 minutes per month from 0°C to 45°C
  • Water resistant or waterproof if placed inside DS9107 iButton capsule (Exceeds Water Resistant 3 ATM requirements)
Common iButton Features
  • Digital identification and information by momentary contact
  • Unique, factory-lasered and tested 64-bit registration number (8-bit family code + 48-bit serial number + 8-bit CRC tester) assures absolute traceability because no two parts are alike
  • Multidrop controller for 1-Wire net

DS18B20
Programmable Resolution 1-Wire Digital Thermometer

  • Unique 1-Wire® Interface Requires Only One Port Pin for Communication
  • Reduce Component Count with Integrated Temperature Sensor and EEPROM
  • Parasitic Power Mode Requires Only 2 Pins for Operation (DQ and GND)

DS18S20-PAR
Parasite-Power Digital Thermometer

  • Unique 1-Wire Interface Requires Only One Port Pin for Communication
  • Derives Power from Data Line ("Parasite Power")—Does Not Need a Local Power Supply
  • Multi-Drop Capability Simplifies Distributed Temperature Sensing Applications

DS18B20-PAR
1-Wire Parasite-Power Digital Thermometer

  • Unique 1-Wire Interface Requires Only One Port Pin for Communication
  • Derives Power from Data Line ("Parasite Power")—Does Not Need a Local Power Supply
  • Multi-Drop Capability Simplifies Distributed Temperature Sensing Applications

DS2432
1Kb Protected 1-Wire EEPROM with SHA-1 Engine

  • 1128 Bits of 5V EEPROM Memory Partitioned Into Four Pages of 256 Bits, a 64-Bit Write-Only Secret, and Up to Five General-Purpose Read/Write Registers
  • On-Chip 512-Bit ISO/IEC 10118-3 SHA-1 Engine to Compute 160-Bit Message Authentication Codes (MACs) and to Generate Secrets
  • Write Access Requires Knowledge of the Secret and the Capability of Computing and Transmitting a 160-Bit MAC as Authorization

DS2450
1-Wire Quad A/D Converter

  • Four high-impedance inputs to measure analog voltages over the 1-Wire bus
  • User programmable input range (2.56V, 5.12V), resolution (1 to 16 bits) and alarm thresholds
  • 5V, single supply operation

DS1973
iButton 4Kb EEPROM

  • 4096 bits Electrically Erasable Programmable Read Only Memory (EEPROM)
  • Overdrive mode boosts communication speed to 142kbps
  • 256-bit scratchpad ensures integrity of data transfer

DS1971
iButton 256-Bit EEPROM

  • 256-bit Electrically Erasable Programmable Read Only Memory (EEPROM) communicates with the economy of one signal plus ground
  • EEPROM organized as one 256-bit page
  • 64-bit one-time programmable application register is automatically write-protected after programming

DS1920
Temperature iButton

  • Digital Thermometer Measures Temperatures from -55°C to +100°C in Typically 0.2s
  • Zero Standby Power
  • 0.5°C Resolution, Digital Temperature Reading is Two's Complement of °C Value