LM95241 datasheet(8/19 Pages) NSC

8 / 19 page

1.0 Functional Description (Continued)

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 guaranteed 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 transis-

tor.

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:

Most-Significant-Byte (MSB) Local Temperature Regis-

ter

Least-Significant-Byte (LSB) Local Temperature Regis-

ter

MSB Remote Temperature 1 Register

LSB Remote Temperature 1 Register

MSB Remote Temperature 2 Register

LSB Remote Temperature 2 Register

Status Register: busy, diode fault

Configuration Register: resolution control, conversion

rate control, standby control

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

1.1 CONVERSION SEQUENCE

In the power up default state the LM95241 typically takes

77.8 ms to convert the Local Temperature, Remote Tem-

perature 1 and 2, and to update all of its registers. Only

during the conversion process is the busy bit (D7) in the

Status register (02h) high. These conversions are addressed

in a round robin sequence. The conversion rate may be

modified by the Conversion Rate bits found in the Configu-

ration Register (03h). When the conversion rate is modified a

delay is inserted between conversions, the actual maximum

conversion time remains at 88.9 ms. Different conversion

rates will cause the LM95241 to draw different amounts of

supply current as shown in Figure 1.

1.2 POWER-ON-DEFAULT STATES

LM95241 always powers up to these known default states.

The LM95241 remains in these states until after the first

conversion.

Command Register set to 00h

Local Temperature set to 0˚C until the end of the first

conversion

Remote Diode Temperature set to 0˚C until the end of

the first conversion

Remote Diode digital filters are on.

Remote Diode 1 model is set to Intel processor on 65nm

or 90nm process with TruTherm Mode enabled. Remote

Diode 2 model is set to 2N3904/MMBT3904 with TruTh-

erm mode disabled.

Status Register depends on state of thermal diode in-

puts

Configuration register set to 00h; continuous conversion

1.3 SMBus INTERFACE

The LM95241 operates as a slave on the SMBus, so the

SMBCLK line is an input and the SMBDAT line is bidirec-

tional. The LM95241 never drives the SMBCLK line and it

does not support clock stretching. According to SMBus

specifications, the LM95241 has a 7-bit slave address. All

bits A6 through A0 are internally programmed and cannot be

changed by software or hardware. The SMBus slave ad-

dress is dependent on the LM95241 part number ordered:

Version

A6 A5 A4 A3 A2 A1 A0

LM95241CIMM

010101

LM95241CIMM-1

001100

LM95241CIMM-2

010101

1.4 TEMPERATURE DATA FORMAT

Temperature data can only be read from the Local and

Remote Temperature registers .

Remote temperature data with the digital filter off is repre-

sented by an 11-bit, two’s complement word or unsigned

binary word with an LSb (Least Significant Bit) equal to

20199706

FIGURE 1. Conversion Rate Effect on Power Supply

Current

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