TMP102 datasheet(11/19 Pages) TI

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SMBus ALERT FUNCTION

HIGH-SPEED (Hs) MODE

TIMEOUT FUNCTION

NOISE

GENERAL CALL

TMP102

SCL

SDA

GND

V+

ALERT

ADD0

10nF

SupplyVoltage

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.

the

ALERT

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 THIGH or falling below TLOW.

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 THIGH; this bit is high if the

switches

the

input

and

output

filters

back

temperature is less than TLOW. 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. RF in Figure 11 should be less

acknowledges

the

General

Call

address

and

than 5k

Ω and CF 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

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