Datasheet

Thermochron iButton Device
Maxim Integrated 7
DS1921G
Detailed Description
The DS1921G is an ideal device to monitor the temper-
ature of any object it is attached to or shipped with,
such as perishable goods or containers of temperature-
sensitive chemicals. The general-purpose battery-
backed SRAM can store an electronic copy of shipping
information, date of manufacture and other important
data written as clear as well as encrypted files. Note
that the initial sealing level of the DS1921G achieves
IP56. Aging and use conditions can degrade the
integrity of the seal over time, therefore, for applications
with significant exposure to liquids, sprays, or other
similar environments, it is recommended to place the
Thermochron in the DS9107 capsule. The DS9107 pro-
vides 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 ).
Overview
Figure 1 shows the relationships between the major
control and memory sections of the DS1921G. The
device has seven main data components: 64-bit
lasered ROM; 256-bit scratchpad; 4096-bit general-
purpose SRAM; 256-bit register page of timekeeping,
control, and counter registers; 96 bytes of alarm time-
stamp and duration logging memory; 126 bytes of
histogram memory; and 2048 bytes of data-log mem-
GENERAL-PURPOSE
SRAM
ALARM TIMESTAMP AND
DURATION LOGGING
MEMORY
REGISTER PAGE
MEMORY
FUNCTION
CONTROL
64-BIT
LASERED
ROM
256-BIT
SCRATCHPAD
CONTROL
LOGIC
32.768kHz
OSCILLATOR
3V LITHIUM
IO
TEMPERATURE
CORE
DATA-LOG MEMORY
INTERNAL
TIMEKEEPING,
CONTROL REGISTERS,
AND COUNTERS
HISTOGRAM
MEMORY
ROM
FUNCTION
CONTROL
1-Wire PORT
PARASITE-POWERED
CIRCUITRY
DS1921G
Figure 1. Block Diagram