LM95241

www.ti.com

SNIS143E – AUGUST 2006 – REVISED MARCH 2013

FUNCTIONAL DESCRIPTION

The LM95241 is a digital sensor that can sense the temperature of 3 thermal zones using a sigma-delta analog-

to-digital converter. It can measure its local die temperature and the temperature of two external transistor

junctions using a

Intel processor on 65nm or 90mn process thermal diode or a 2N3904 diode connected transistor. The transistor

type is register programmable and does not require software intervention after initialization. The LM95241 has an

advanced input stage using Texas Instruments' TruTherm technology that reduces the spread in non-ideality

found in Intel processors on 65nm or 90nm process. Internal analog filtering has been included in the thermal

diode input stage thus minimizing the need for external thermal diode filter capacitors. In addition a digital filter

has been added. These noise immunity improvements in the analog input stage along with the digital filtering will

allow longer trace tracks or cabling to the thermal diode than previous thermal diode sensor devices.

The 2-wire serial interface, of the LM95241, is compatible with SMBus 2.0 and I2C. Please see the SMBus 2.0

specification for a detailed description of the differences between the I2C bus and SMBus.

The temperature conversion rate is programmable to allow the user to optimize the current consumption of the

LM95241 to the system requirements. The LM95241 can be placed in shutdown to minimize power consumption

when temperature data is not required. While in shutdown, a 1-shot conversion mode allows system control of

the conversion rate for ultimate flexibility.

The remote diode temperature resolution is variable and depends on whether the digital filter is activated. When

the digital filter is active the resolution is thirteen bits and is programmable to 13-bits unsigned or 12-bits plus

sign, with a least-significant-bit (LSb) weight for both resolutions of 0.03125°C. When the digital filter is inactive

the resolution is eleven bits and is programmable to 11-bits unsigned or 10-bits plus sign, with a least-significant-

bit (LSb) weight for both resolutions of 0.125°C. The unsigned resolution allows the remote diodes to sense

temperatures above 127°C. Local temperature resolution is not programmable and is always 9-bits plus sign and

has a 0.25°C LSb.

The LM95241 remote diode temperature accuracy is trimmed for the typical thermal diode of a Intel processor on

65nm or 90nm process or a typical 2N3904 transistor and the accuracy is ensured only when using either of

these diodes when selected appropriately. TruTherm mode should be enabled when measuring a Intel processor

on 65nm or 90nm process and disabled when measuring a 3904 transistor.

Diode fault detection circuitry in the LM95241 can detect the presence of a remote diode.

The LM95241 register set has an 8-bit data structure and includes:

1. Most-Significant-Byte (MSB) Local Temperature Register

2. Least-Significant-Byte (LSB) Local Temperature Register

3. MSB Remote Temperature 1 Register

4. LSB Remote Temperature 1 Register

5. MSB Remote Temperature 2 Register

6. LSB Remote Temperature 2 Register

7. Status Register: busy, diode fault

8. Configuration Register: resolution control, conversion rate control, standby control

9. Remote Diode Filter Setting

10. Remote Diode Model Select

11. Remote Diode TruTherm Mode Control

12. 1-shot Register

13. Manufacturer ID

14. Revision ID

Copyright © 2006–2013, Texas Instruments Incorporated

Submit Documentation Feedback

9

Product Folder Links: LM95241