DS1821

2 of 19

ORDERING INFORMATION

PART

PACKAGE MARKING

PIN-PACKAGE

DS1821C+

DS1821

3 TO92

DS1821S+

DS1821S

8 SO (208 mils)

DS1821S+T&R

DS1821S

8 SO (208 mils), 2000 Piece

Tape-and-Reel

+Denotes a lead(Pb)-free/RoHS-compliant package.

T&R = Tape and reel.

DETAILED PIN DESCRIPTIONS Table 1

TO92

8-PIN

SO*

SYMBOL

DESCRIPTION

1

2

GND

Ground pin.

2

1

DQ

Open drain data input/output pin – 1-Wire operation; Open drain

thermostat output pin –thermostat operation.

3

8

Power supply pin.

*All pins not specified in this table are “No Connect” pins.

OVERVIEW

Figure 1 shows a block diagram of the DS1821 and pin descriptions are given in Table 1. The DS1821

can operate as a standalone thermostat with user-programmable trip-points or as 8-bit temperature sensor

with a 1-Wire digital interface. The open-drain DQ pin functions as the thermostat output for thermostat

operation and as the data I/O pin for 1-Wire communications. The 1-Wire interface provides user access

and the temperature register.

When configured as standalone thermostat, temperature conversions start immediately at power-up. In

this mode, the DQ pin becomes active when the temperature of the DS1821 exceeds the limit

The DS1821 uses Maxim’s exclusive 1-Wire bus protocol that implements bus communication with one

control signal. This system is explained in detail in the 1-Wire BUS SYSTEM section of this datasheet.