DS1922T-F5# Maxim Integrated Products, DS1922T-F5# Datasheet - Page 20

• Manufacturer Part Number: DS1922T-F5#
• Description: IBUTTON TEMP LOGGER
• Manufacturer: Maxim Integrated Products
• Series: iButton®r

Specifications of DS1922T-F5#

• Rohs Information: IButton RoHS Compliance Plan
• Memory Size: 512B
• Memory Type: NVSRAM (Non-Volatile SRAM)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Temperature Logger iButton with 8KB
Data-Log Memory
The DS1922L’s temperature range begins at -40°C and
ends at +85°C. The temperature range for the DS1922T
begins at 0 and ends at +125°C. Temperature values
are represented as an 8-bit or 16-bit unsigned binary
number with a resolution of 0.5°C in 8-bit mode and
0.0625°C in 16-bit mode.
The higher temperature byte TRH is always valid. In
16-bit mode, only the three highest bits of the lower
byte TRL are valid. The five lower bits all read 0. TRL is
undefined if the device is in 8-bit temperature mode. An
out-of-range temperature reading is indicated as 00h or
0000h when too cold and FFh or FFE0h when too hot.
With TRH and TRL representing the decimal equivalent
of a temperature reading, the temperature value is cal-
culated as:
Table 1. Temperature Conversion Examples
Table 2. Temperature Alarm Threshold Examples
20
ADDRESS
020Ch
020Dh
______________________________________________________________________________________
MODE
16-Bit
16-Bit
ϑ(°C) = TRH/2 - 41 + TRL/512 (16-bit mode,
8-Bit
8-Bit
65.5
30.0
ϑ(°C) = TRH/2 - 41 (8-bit mode, TLFS = 0,
(°C)
TLFS = 1, see address 0213h)
BIT 7
T10
T2
see address 0213h)
HEX
54h
17h
54h
17h
Temperature Conversion
HEX
85h
3Eh
BIT 6
TALM (DS1922T)
T1
T9
TRH
DECIMAL
BIT 5
T0
T8
DECIMAL
84
23
84
23
133
62
Latest Temperature Conversion Result Register Bitmap
BIT 4
T7
0
HEX
00h
60h
—
—
This equation is valid for converting temperature read-
ings stored in the data-log memory as well as for data
read from the Latest Temperature Conversion Result
register. The “-41” applies to the DS1922L. For the
DS1922T, use “-1” instead of “-41.”
To specify the temperature alarm thresholds, the previ-
ous equations are resolved to:
The “+82” applies to the DS1922L. For the DS1922T, use
“+2.” Because the temperature alarm threshold is only
one byte, the resolution or temperature increment is limit-
ed to 0.5°C. The TALM value must be converted into
hexadecimal format before it can be written to one of the
Temperature Alarm Threshold registers (Low Alarm
address 0208h; High Alarm address 0209h).
Independent of the conversion mode (8-bit or 16-bit),
only the most significant byte of a temperature conver-
sion is used to determine whether an alarm is generated.
BIT 3
T6
0
TRL
-10.0
DECIMAL
25.5
(°C)
BIT 2
96
—
—
0
T5
0
TALM = 2 x ϑ(°C) + 82
BIT 1
T4
0
DS1922L
-29.3125
HEX
85h
3Eh
1.000
-29.5
1.0
TALM (DS1922L)
BIT 0
T3
0
(°C)
DECIMAL
DS1922T
10.6875
41.000
133
41.0
10.5
62
BYTE
TRH
TRL