DS1482

1-Wire Level Shifter and Line Driver with Load Sensor


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Description

The DS1482 is a simple 1-Wire® line driver with load sensor and level shifter, designed to function as an interface between a 3V host system and a 1-Wire system that runs on 5V. Two supplies are provided, a 5V supply for the 1-Wire operations (VCC) and an interface supply (VCCQ). The DS1482 can connect directly to a synchronous serial port if it supports the appropriate bit rates to generate 1-Wire timing.

Figure 1, of the full data sheet, shows the DS1482 block diagram. TXD is buffered and controls an N-channel transistor, which drives the 1-Wire pin I/O low, e.g., to initiate a time slot. The logic level of the I/O pin is returned through a level-shifting buffer to the RXD pin for the host processor to read. Figure 3, of the full data sheet, shows the relationship of these signals in case of a 1-Wire read time slot.

The SPU input generates a control signal (PCTLZ) for an external low-impedance PMOS transistor (Figure 2 of the full data sheet) that bypasses the 1-Wire pullup resistor (RPUP) to provide power for 1-Wire devices with a high-load current. PCTLZ is gated by the inverted TXD signal. This prevents a high through-current in case TXD and SPU are high at the same time.

The DS1482 contains a high-precision comparator because it is important for the host micro to know when the high load on the 1-Wire side is no longer active. As shown in Figure 4, of the full data sheet, the high current load causes a small drop of the voltage on the I/O pin. The comparator detects when the high current phase ends, and enables DONE after the deglitching time tCF is over. The START signal allows the host micro to selectively enable DONE.

Key Features

  • Works with All iButtons® and 1-Wire Devices
  • Communicates at Regular and Overdrive 1-Wire Speed (Host-Dependent)
  • Separate Interface Power Supply to Level Shift to Non-5V Systems
  • External Strong-Pullup Control Pin can be Used to Provide Low-On-Resistance-High Current Power Source
  • Load Sensor to Detect when Strong-Pullup Power Delivery is no Longer Needed
  • Power Delivery DONE Signal can be Connected to Host Interrupt
  • Low-Cost 16-Pin SO Surface-Mount Package
  • Operating Temperature Range: -40°C to +85°C

Applications/Uses

  • 3.3V Processor Systems Requiring a 5V 1-Wire Interface
Product Reliability Reports: DS1482.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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