2-WIRE SERIAL TEMPERATURE
SENSOR AND THERMAL MONITOR
PRELIMINARY INFORMATION
TCN75
Address Byte
Immediately following the Start Condition, the host must
next transmit the address byte to the TCN75. The four most
significant bits of the Address Byte (A6, A5, A4, A3) are fixed
to 1001(B). The states of A2, A1 and A0 in the serial bit
stream must match the states of the A2, A1 and A0 address
inputs for the TCN75 to respond with an Acknowledge
(indicating the TCN75 is on the bus and ready to accept
data). The eighth bit in the Address Byte is a Read-Write Bit.
This bit is a 1 for a read operation or 0 for a write operation.
Acknowledge (ACK)
Acknowledge (ACK) provides a positive handshake
between the host and the TCN75. The host releases SDA
after transmitting eight bits then generates a ninth clock
cycle to allow the TCN75 to pull the SDA line LOW to
acknowledge that it successfully received the previous eight
bits of data or address.
Data Byte
After a successful ACK of the address byte, the host
must next transmit the data byte to be written or clock out the
data to be read. (See the appropriate timing diagrams.) ACK
will be generated after a successful write of a data byte into
the TCN75.
Stop Condition (STOP)
Communications must be terminated by a stop condi-
tion (a LOW to HIGH transition of SDA while SCL is HIGH).
The Stop Condition must be communicated by the transmit-
ter to the TCN75.
Power Supply
To minimize temperature measurement error, the
TCN75VO_-3 is factory calibrated at a supply voltage of
3.3V
±5V
and the TCN75CO_-5 is factory calibrated at a
supply voltage of 5V
±5%.
Either device is fully operational
ERROR (°0)
over the power supply voltage range of 2.7V to 5.5V, but
with a lower measurement accuracy. Figure 2 shows the
worst case temperature measurement error for the
TCN75CO_-3 operated at a power supply voltage of 5V
±
10%. Figure 3 shows the worst case temperature measure-
ment error for the TCN75CO_-3 operated at a power supply
voltage of 3.3V
±10%.
±5
±4
ERROR (°0)
±3
±2
±1
20
35
50
65
80
95
110
125
TCN75 Case Temeprature (°C)
Figure 2. TCN75CO_-3 Measurement Error at V
DD
= 5V
±
10%
±5
±4
±3
±2
±1
+V
DD
(3V to 5.5V)
C
Bypass
8
A
0
Address
(Set as Desired) A
1
A
2
7
6
5
TCN75
I
2
C Interface SDA
SCL
1
2
4
0.1µF Recommended
Unless Device is Mounted
Close to CPU
20
35
50
65
80
95
110
125
TCN75 Case Temeprature (°C)
Figure 3. TCN75CO_-5 Measurement Error at V
DD
= 3.3V
±
10%
3
TO PROCESSOR
INT/CMPTR
Figure 1. Typical Application
TCN75-04 6/16/97
5
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
