Datasheet

TMP411-Q1
SBOS527F –DECEMBER 2010–REVISED NOVEMBER 2013 www.ti.com
SMBUS ALERT FUNCTION UNDERVOLTAGE LOCKOUT
The TMP411-Q1 supports the SMBus alert function. The TMP411-Q1 senses when the power-supply
When pin 6 is configured as an alert output, the voltage has reached a minimum voltage level for the
ALERT pin of the TMP411-Q1 may be connected as ADC converter to function. The detection circuitry
an SMBus alert signal. When a master detects an consists of a voltage comparator that enables the
alert condition on the ALERT line, the master sends ADC converter after the power supply (V+) exceeds
an SMBus alert command (0001 1001) on the bus. If 2.45 V (typical). The comparator output is
the ALERT pin of the TMP411-Q1 is active, the continuously checked during a conversion. The
device acknowledges the SMBus alert command and TMP411-Q1 does not perform a temperature
responds by returning its slave address on the SDA conversion if the power-supply output is not
line. The eighth bit (LSB) of the slave address byte adequate. The last valid measured temperature is
indicates whether the temperature exceeding one of used for the temperature measurement result.
the temperature high limit settings or falling below
one of the temperature low limit settings caused the GENERAL-CALL RESET
alert condition. This bit will is if the temperature is
The TMP411-Q1 supports reset via the two-wire
greater than or equal to one of the temperature high-
general-call address 00h (0000 0000b). The TMP411-
limit settings; this bit is low if the temperature is less
Q1 acknowledges the general-call address and
than one of the temperature low-limit settings. See
responds to the second byte. If the second byte is
Figure 17 for details of this sequence.
06h (0000 0110b), the TMP411-Q1 executes a
If multiple devices on the bus respond to the SMBus software reset. This software reset restores the
alert command, arbitration during the slave address power-on-reset state to all TMP411-Q1 registers,
portion of the SMBus alert command determines aborts any conversion in progress, and clears the
which device clears its alert status. If the TMP411-Q1 ALERT and THERM pins. The TMP411-Q1 takes no
wins the arbitration, its ALERT pin becomes inactive action in response to other values in the second byte.
at the completion of the SMBus alert command. If the
TMP411-Q1 loses the arbitration, the ALERT pin IDENTIFICATION REGISTERS
remains active.
The TMP411-Q1 allows for the two-wire bus
controller to query the device for manufacturer and
SHUTDOWN MODE (SD)
device IDs. This feature allows for software
The TMP411-Q1 shutdown mode allows the user to identification of the device at the particular two-wire
save maximum power by shutting down all device bus address. The manufacturer ID is obtained by
circuitry other than the serial interface, reducing reading from pointer address FEh. The TMP411-Q1
current consumption to typically less than 3 μA; see manufacturer code is 55h. The device ID depends on
typical characteristic curve Shutdown Quiescent the specific model; see the Register Map (Table 4).
Current vs Supply Voltage. Shutdown mode is These registers are read-only.
enabled when the SD bit of the Configuration
Register is high; the device shuts down once the FILTERING
current conversion is completed. When SD is low, the
Remote junction temperature sensors are usually
device maintains a continuous conversion state.
implemented in a noisy environment. Noise is most
often created by fast digital signals, and it can corrupt
SENSOR FAULT
measurements. The TMP411-Q1 has a built-in 65-
The TMP411-Q1 senses a fault at the D+ input kHz filter on the inputs of D+ and D− to minimize the
resulting from incorrect diode connection or an open effects of noise. However, a bypass capacitor placed
circuit. The detection circuitry consists of a voltage differentially across the inputs of the remote
comparator that trips when the voltage at D+ exceeds temperature sensor is recommended to make the
(V+) − 0.6 V (typical). The comparator output is application more robust against unwanted coupled
continuously checked during a conversion. If a fault is signals. The value of the capacitor should be
detected, the last valid measured temperature is used between 100 pF and 1 nF. Some applications attain
for the temperature measurement result, the OPEN better overall accuracy with additional series
bit (Status Register, bit 2) is set high, and, if the alert resistance; however, this increased accuracy is
function is enabled, ALERT asserts low. setup-specific. When series resistance is added, the
value should not be greater than 3 kΩ.
When not using the remote sensor with the TMP411-
Q1, the D+ and D− inputs must be connected If filtering is needed, the suggested component
together to prevent meaningless fault warnings. values are 100 pF and 50 Ω on each input. Exact
values are application-specific.
28 Submit Documentation Feedback Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: TMP411-Q1