Datasheet

LM95234
www.ti.com SNIS136D –AUGUST 2006–REVISED MARCH 2013
FUNCTIONAL DESCRIPTION
LM95234 is an 11-bit digital temperature sensor with a 2-wire System Management Bus (SMBus) interface that
can monitor the temperature of four remote diodes as well as its own temperature. The LM95234 can be used to
very accurately monitor the temperature of up to four external devices such as microprocessors, graphics
processors or diode-connected 2N3904 transistor. The LM95234 includes TruTherm BJT beta compensation
technology that allows sensing of Intel processors 90 nm or 65 nm process thermal diodes accurately.
The LM95234 reports temperature in two different formats for +127.875°C/–128°C range and 0°C/255°C range.
The LM95234 has a Sigma-Delta ADC (Analog-to-Digital Converter) core which provides the first level of noise
imunity. For improved performance in a noisy environment the LM95234 includes programmable digital filters for
Remote Diode 1 and 2 temperature readings. When the digital filters are invoked the resolution for Remote Diode
1 and 2 readings increases to 0.03125°C. The LM95234 contains a diode model selection register that includes
bits for each channel that select between thermal diodes of Intel processors on 65 nm process or 2N3904s. For
maximum flexibility and best accuracy the LM95234 includes offset registers that allow calibration of other diode
types.
Diode fault detection circuitry in the LM95234 can detect the absence or fault state of a remote diode: whether
D+ is shorted to V
DD
, D- or ground, or whether D+ is floating.
The LM95234 TCRIT1, TCRIT2 and TCRIT3 active low outputs are triggered when any unmasked channel
exceeds its corresponding programmable limit and can be used to shutdown the system, to turn on the system
fans or as a microcontroller interrupt function. The current status of the TCRIT1, TCRIT2 and TCRIT3 pins can
be read back from the status registers via the SMBus interface. Two of the remote channels have two separate
limits each that control the TCRIT1 and TCRIT2 pins. The remaining two channels and the local channel each
have one limit to control both the TCRIT1 and TCRIT2 pins. The TCRIT3 pin shares the limits of the TCRIT2 pin
but allows for different masking options. All limits have a shared programmable hysteresis register.
Remote Diode 1 and 2 temperature channels have programmable digital filters while the other two remote
temperature channels utilize a fault-queue in order to avoid false triggering the TCRIT pins.
LM95234 has a three-level address pin to connect up to 3 devices to the same SMBus master. LM95234 also
has programmable conversion rate register as well as a shutdown mode for power savings. One round of
conversions can be triggered in shutdown mode by writing to the one-shot register through the SMBus interface.
LM95234 can be programmed to turn off unused channels for more power savings.
The LM95234 register set has an 8-bit data structure and includes:
1. Temperature Value Registers with signed format
– Most-Significant-Byte (MSB) and Least-Significant-Byte (LSB) Local Temperature
– MSB and LSB Remote Temperature 1
– MSB and LSB Remote Temperature 2
– MSB and LSB Remote Temperature 3
– MSB and LSB Remote Temperature 4
2. Temperature Value Registers with unsigned format
– MSB and LSB Remote Temperature 1
– MSB and LSB Remote Temperature 2
– MSB and LSB Remote Temperature 3
– MSB and LSB Remote Temperature 4
3. Diode Configuration Registers
– Diode Model Select
– Remote 1 Offset
– Remote 2 Offset
– Remote 3 Offset
– Remote 4 Offset
4. General Configuration Registers
– Configuration (Standby, Fault Queue enable for Remote 3 and 4; Conversion Rate)
– Channel Conversion Enable
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