DS1482S/TR 데이터 시트보기 (PDF) - Maxim Integrated

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DS1482S/TR

1-Wire Level Shifter and Line Driver with Load Sensor

Maxim Integrated 

www.maxim-ic.com

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

DS1482

1-Wire Level Shifter and Line Driver

with Load Sensor

PIN ASSIGNMENT

1 VCCQ

N.C. 2

SPU 3

START 4

TXD 5

N.C. 6

GND 7

N.C. 8

16 VCC

15 N.C.

14 PCTLZ

13 DONE

12 RXD

11 N.C.

10 I/O

9 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

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 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

(Figure 2) 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when the high load on the 1-Wire side is no longer active.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, 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.

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

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