CAT34TS02 Datasheet, PDF (6/22 Pages) ON Semiconductor – Digital Output Temperature Sensor with On-board SPD EEPROM

CAT34TS02
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 accept the device
address. These pins have on-chip pull-down resistors.
E¯¯V¯E¯N¯T¯: The open-drain E¯¯V¯E¯N¯T¯ pin can be
programmed to signal over/under temperature limit
conditions.
POWER-ON RESET (POR)
The CAT34TS02 incorporates Power-On Reset
(POR) circuitry which protects the device against
powering up to invalid state. The TS component will
power up into conversion mode after V_CC exceeds
the TS POR trigger level and the SPD component
will power up into standby mode after V_CC exceeds
the SPD POR trigger level. Both the TS and SPD
components will power down into Reset mode when
V_CC drops below their respective POR trigger levels.
This bi-directional POR behavior protects the
CAT34TS02 against brown-out failure following a
temporary loss of power. The POR trigger levels are
set below the minimum operating V_CC level.
DEVICE INTERFACE
The CAT34TS02 supports the Inter-Integrated
Circuit (I²C) and the System Management Bus
(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 Ma ster device, which
generates the serial clock and the START and
STOP conditions. The CAT34TS02 acts as a Slave
device. Master and Slave alternate as transmitter
and receiver. Up to 8 CAT34TS02 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 1).
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 either the Temperature
Sensor (TS) registers (0011) or the EEPROM memory
contents (1010), as shown in Figure 2. The next 3 bits,
A2, A1 and A0, select one of 8 possible 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 3). 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 4.
Doc. No. MD-1129 Rev. G
6
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Characteristics subject to change without notice