PIN CONFIGURATIONS

PIN

NAME

FUNCTION

TO-92

1,2,6,

7,8

—

N.C.

No Connection

3

 

3

 

VDD

Optional VDD. VDD must be grounded for operation

in parasite power mode.

4

 

 

2

 

 

DQ

Data Input/Output. Open-drain 1-Wire interface pin.

Also provides power to the device when used in parasite

power mode (see the Powering the DS18B20 section.)

5

1

GND

Ground

 

OVERVIEW

Figure 1 shows a block diagram of the DS18B20, and pin descriptions are given in the Pin Description

table. The 64-bit ROM stores the device’s unique serial code. The scratchpad memory contains the 2-byte

temperature register that stores the digital output from the temperature sensor. In addition, the scratchpad

provides access to the 1-byte upper and lower alarm trigger registers (TH and TL) and the 1-byte

configuration register. The configuration register allows the user to set the resolution of the temperature-

to-digital conversion to 9, 10, 11, or 12 bits. And there are 2-byte user programmable EEPROM. The

TH, TL, configuration registers, and 2-byte user programmable EEPROM are nonvolatile (EEPROM), so

they will retain data when the device is powered down.

 

The DS18B20 uses 1-Wire bus protocol that implements bus communication using one control signal. The

control line requires a weak pullup resistor since all devices are linked to the bus via a 3-state or open-drain

port (the DQ pin in the case of the DS18B20). In this bus system, the microprocessor (the master device)

identifies and addresses devices on the bus using each device’s unique 64-bit code. Because each device has

a unique code, the number of devices that can be addressed on one bus is virtually unlimited. The 1-Wire

UMW

R

UMW DS18B20

www.umw-ic.com

2

友台半导体有限公司