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DS1841

Temperature-Controlled, NV, I

Logarithmic Resistor

8 _______________________________________________________________________________________

Temperature Conversion and Supply

Voltage Monitoring

Temperature Conversion

The DS1841 features an internal 8-bit temperature sen-

sor that can drive the LUT and provide a measurement

of the ambient temperature over I

C by reading the

value stored in address 0Ch. The sensor is functional

over the entire operating temperature range and is

stored in signed two’s complement format with a resolu-

tion of 1°C/bit. See Table 2, Register 0Ch description for

the temperature sensor’s bit weights. To calculate the

temperature, treat the two’s complement binary value as

an unsigned binary number, then convert it to decimal.

If the result is greater than or equal to 128, subtract 256

from the result.

LUT

The DS1841 monitors the internal temperature by

repeatedly polling the sensor’s result with update rate

FRAME

. During each cycle, the DS1841 reads the inter-

nal temperature, and, based on that temperature,

points to the corresponding LUT address. Every two

degrees of temperature will convert into one tempera-

ture address slot. See Table 3 for a list of temperatures

and their corresponding LUT addresses.

The LUT features one-degree hysteresis to prevent

chattering if the measured temperature falls on the

boundary between two windows (see Figure 1).

Table 3. LUT Registers and Temperature Ranges

TEMPERATURE (°C)

TEMPERATURE VALUE FOR GIVEN

TEMPERATURE (HEX)

CORRESPONDING LUT ADDRESS

(HEX)

-40 or less D8 80

-39 to -38 D9 to DA 81

-37 to -36 DB to DC 82

-35 to -34 DD to DE 83

— — —

+95 to +96 5F to 60 C4

+97 to +98 61 to 62 C5

+99 to +100 63 to 64 C6

+101 or more 65 C7

LUT Mode and LUT Adder Mode Block Diagram (Update Mode Bit = 1)

1 OF 128 MULTIPLEXERS

IVR

ON POWER-UP

ONLY WHEN IN

LUT ADDER MODE

INITIAL VALUE REGISTER (IVR)

00h*

CONTROL

LOGIC/

REGISTERS

LUT

ADDRESS

(LUTAR)

08h

72-BYTE

LOOKUP

TABLE

(LUT)

80h–C7h

WIPER

(WR)

09h*

ADC

INTERFACE

TEMP

SENSOR

VOLTAGE

TEMP

0Ch

(V)

0Eh

GND

SCL

SDA

POS 7Fh

POS 00h

RGND

CONTROL

DATA

*NOTE THAT WHEN IN LUT OR LUT ADDER MODE, WR IS ACCESSED THROUGH 09h WHILE IVR REMAINS AT 00h.

∑

LUTVAL

IVR

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

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