DS1925 datasheet(6/46 Pages) MAXIM

6 / 46 page

Detailed Description

The DS1925 is an ideal device to monitor for extended

time periods the temperature of any object it is attached to

or shipped with, such as fresh produce, medical drugs, and

supplies, and for use in refrigerators and freezers. Note

that the initial sealing level of the DS1925 achieves IP56.

Aging and use conditions can degrade the integrity of the

seal over time, so for applications with significant expo-

sure to liquids, sprays, or other similar environments, it is

recommended to place the DS1925 in the DS9107 iButton

capsule. The DS9107 provides a watertight enclosure that

has been rated to IP68 (refer to

Application Note 4126:

Understanding the IP (Ingress Protection) Ratings

of iButton Data Loggers and Capsule). Software for

setup and data retrieval through the 1-Wire interface is

available for free download from the Maxim website at

www.maximintegrated.com/1-wiredrivers. This soft-

ware also includes drivers for the serial and USB port of a

PC, and routines to access the general-purpose memory

for storing application- or equipment-specific data files.

Overview

Figure 1 shows the relationships between the DS1925’s

major control and memory sections. The device has five

main data components: 1) 64-bit lasered ROM, 2) 256-bit

scratchpad, 3) 512-byte general-purpose memory, 4) two

256-bit register pages of timekeeping, control, status, and

counter registers and passwords, and 5) 122KB of data-

logging memory. Except for the ROM and the scratchpad,

all other memory is arranged in a single linear address

space. The data-logging memory, counter registers, and

several other registers are read-only for the user. Both

programmed for a mission. The password registers, one

for a read password and another one for a read/write

password, can only be written, never read.

Figure 2 shows the hierarchical structure of the 1-Wire

protocol. The bus master must first provide one of the

eight ROM function commands: 1) Read ROM, 2) Match

ROM, 3) Search ROM, 4) Conditional Search ROM, 5)

Skip ROM, 6) Overdrive-Skip ROM, 7) Overdrive-Match

ROM, or 8) Resume. Upon completion of an Overdrive

ROM command byte executed at standard speed, the

device enters overdrive mode, where all subsequent com-

munication occurs at a higher speed. Figure 12 describes

the protocol required for these ROM function commands.

After a ROM function command is successfully executed,

the memory and control functions become accessible

and the master can provide any one of the eight available

commands. Figure 9 describes the protocol for these

memory and control function commands.

All data is read

and written least significant bit first.

DS1925

iButton High-Capacity Temperature Logger

with 122KB Data-Log Memory

www.maximintegrated.com

Maxim Integrated │ 6

Pin Configuration

Pin Description

5.89mm

0.51mm

BRANDING

F5 SIZE

GND

17.35mm

16.25mm

1-Wire

000000FBC52B

Thermochron®

NAME

FUNCTION

Input/Output

GND

Ground

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