Data Sheet

SMBus ALERT FUNCTION HIGH-SPEED (Hs) MODE
TIMEOUT FUNCTION
NOISE
GENERAL CALL
TMP102
SCL SDA
GND V+
ALERT ADD0
C
F
10nF³
R
F
5k£ W
SupplyVoltage
TMP102
www.ti.com ............................................................................................................................................... SBOS397B – AUGUST 2007 – REVISED OCTOBER 2008
The TMP102 supports the SMBus Alert function. In order for the two-wire bus to operate at frequencies
When the TMP102 operates in Interrupt mode (TM = above 400kHz, the master device must issue an
'1'), the ALERT pin may be connected as an SMBus Hs-mode master code (00001xxx) as the first byte
Alert signal. When a master senses that an ALERT after a START condition to switch the bus to
condition is present on the ALERT line, the master high-speed operation. The TMP102 does not
sends an SMBus Alert command (00011001) to the acknowledge this byte, but switches its input filters on
bus. If the ALERT pin is active, the device SDA and SCL and its output filters on SDA to operate
acknowledges the SMBus Alert command and in Hs-mode, allowing transfers at up to 3.4MHz. After
responds by returning its slave address on the SDA the Hs-mode master code has been issued, the
line. The eighth bit (LSB) of the slave address byte master transmits a two-wire slave address to initiate a
indicates if the ALERT condition was caused by the data transfer operation. The bus continues to operate
temperature exceeding T
HIGH
or falling below T
LOW
. in Hs-mode until a STOP condition occurs on the bus.
For POL = '0', this bit is low if the temperature is Upon receiving the STOP condition, the TMP102
greater than or equal to T
HIGH
; this bit is high if the switches the input and output filters back to
temperature is less than T
LOW
. The polarity of this bit fast-mode operation.
is inverted if POL = '1'. Refer to Figure 15 for details
of this sequence.
If multiple devices on the bus respond to the SMBus
The TMP102 resets the serial interface if SCL is held
Alert command, arbitration during the slave address
low for 30ms (typ). The TMP102 releases the bus if it
portion of the SMBus Alert command determines
is pulled low and waits for a START condition. To
which device will clear its ALERT status. The device
avoid activating the timeout function, it is necessary
with the lowest two-wire address wins the arbitration.
to maintain a communication speed of at least 1kHz
If the TMP102 wins the arbitration, its ALERT pin
for SCL operating frequency.
becomes inactive at the completion of the SMBus
Alert command. If the TMP102 loses the arbitration,
its ALERT pin remains active.
The TMP102 is a very low-power device and
generates very low noise on the supply bus. Applying
an RC filter to the V+ pin of the TMP102 can further
The TMP102 responds to a two-wire General Call
reduce any noise the TMP102 might propagate to
address (0000000) if the eighth bit is '0'. The device
other components. R
F
in Figure 11 should be less
acknowledges the General Call address and
than 5k Ω and C
F
should be greater than 10nF.
responds to commands in the second byte. If the
second byte is 00000110, the TMP102 internal
registers are reset to power-up values. The TMP102
does not support the General Address acquire
command.
Figure 11. Noise Reduction
Copyright © 2007 – 2008, Texas Instruments Incorporated Submit Documentation Feedback 11
Product Folder Link(s): TMP102