CAT6095_11 Datasheet, PDF (5/15 Pages) ON Semiconductor – Digital Output Temperature Sensor

CAT6095
Pin Description
SCL: The Serial Clock input pin accepts the Serial Clock
generated by the Master (Host).
SDA: The Serial Data I/O pin receives input data and
transmits data stored in the internal registers. In transmit
mode, this pin is open drain. Data is acquired on the positive
edge, and is delivered on the negative edge of SCL.
A0, A1 and A2: The Address pins set the device address.
These pins have on−chip pull−down resistors.
EVENT: The open−drain EVENT pin can be programmed
to signal over/under temperature limit conditions.
Power−On Reset
The CAT6095 incorporates Power−On Reset (POR)
circuitry which monitors the supply voltage, and then resets
(initializes) the internal state machine below a POR trigger
level of approximately 2.0 V, i.e. well below the minimum
recommended V_CC value.
The temperature sensor (TS) powers-up into conversion
mode. The internal state machine will operate properly
above the POR trigger level, but valid temperature readings
can be expected only after the first conversion cycle started
and completed at nominal supply voltage.
Device Interface
The CAT6095 supports I²C and SMBus data transmission
protocols. These protocols describe serial communication
between transmitters and receivers sharing a 2−wire data
bus. Data flow is controlled by a Master device, which
generates the serial clock and the START and STOP
conditions. The CAT6095 acts as a Slave device. Master and
Slave alternate as transmitter and receiver. Up to 8 CAT6095
devices may be present on the bus simultaneously, and can
be individually addressed by matching the logic state of the
address inputs A0, A1, and A2.
I²C/SMBus Protocol
The I²C/SMBus uses two ‘wires’, one for clock (SCL) and
one for data (SDA). The two wires are connected to the V_CC
supply via pull−up resistors. Master and Slave devices
connect to the bus via their respective SCL and SDA pins.
The transmitting device pulls down the SDA line to
‘transmit’ a ‘0’ and releases it to ‘transmit’ a ‘1’.
Data transfer may be initiated only when the bus is not
busy (see A.C. Characteristics).
During data transfer, the SDA line must remain stable
while the SCL line is HIGH. An SDA transition while SCL
is HIGH will be interpreted as a START or STOP condition
(Figure 8).
START
The START condition precedes all commands. It consists
of a HIGH to LOW transition on SDA while SCL is HIGH.
The START acts as a ‘wake−up’ call to all Slaves. Absent a
START, a Slave will not respond to commands.
STOP
The STOP condition completes all commands. It consists
of a LOW to HIGH transition on SDA while SCL is HIGH.
The STOP tells the Slave that no more data will be written
to or read from the Slave.
Device Addressing
The Master initiates data transfer by creating a START
condition on the bus. The Master then broadcasts an 8−bit
serial Slave address. The first 4 bits of the Slave address (the
preamble) select the Temperature Sensor (TS preamble =
0011) as shown in Figure 9. The next 3 bits, A2, A1 and A0,
select one of 8 possible TS Slave devices. The last bit, R/W,
specifies whether a Read (1) or Write (0) operation is being
performed.
Acknowledge
A matching Slave address is acknowledged (ACK) by the
Slave by pulling down the SDA line during the 9^th clock
cycle (Figure 10). After that, the Slave will acknowledge all
data bytes sent to the bus by the Master. When the Slave is
the transmitter, the Master will in turn acknowledge data
bytes in the 9^th clock cycle. The Slave will stop transmitting
after the Master does not respond with acknowledge
(NoACK) and then issues a STOP. Bus timing is illustrated
in Figure 11.
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