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032103

DS1482

1-Wire Level Shifter and Line Driver

with Load Sensor

www.maxim-ic.com

FEATURES

§ Works with All iButtons

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

PIN ASSIGNMENT

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

N.C.

SPU

START

TXD

N.C.

GND

N.C.

N.C.

PCTLZ

DONE

RXD

N.C.

I/O

N.C.

ORDERING INFORMATION

DS1482S

SO-16

DS1482S/T&R

SO-16, Tape-and-Reel

Contact the factory for versions with different

signal polarities.

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

directly to a synchronous serial port if it supports the appropriate bit rates to generate 1-Wire timing.

Figure 1 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 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

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when the high load on the 1-Wire side is no longer active.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, the high current load

causes a small drop of the voltage on the I/O pin. The comparator detects when the high current phase

to selectively enable DONE.

iButton and 1-Wire are registered trademarks of Dallas Semiconductor.