Typical Performance Characteristics

Thermal Diode Capacitor or PCB Leakage Current Effect

Remote Diode Temperature Reading

Remote Temperature Reading Sensitivity to Thermal

Diode Filter Capacitance

20094305

20094307

Conversion Rate Effect on Average Power Supply

Current

20094306

1.0 Functional Description

The LM95221 is a digital sensor that can sense the tempera-

ture of 3 thermal zones using a sigma-delta analog-to-digital

converter. It can measure its local die temperature and the

temperature of two diode connected MMBT3904 transistors

using a

∆V

interface, of the LM95221, 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 LM95221

to the system requirements. The LM95221 can be placed in

shutdown to minimize power consumption when tempera-

ture data is not required. While in shutdown, a 1-shot con-

version mode allows system control of the conversion rate

for ultimate flexibility.

The remote diode temperature resolution is eleven bits and

is programmable to 11-bits unsigned or 10-bits plus sign.

The least-significant-bit (LSb) weight for both resolutions is

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 LM95221 remote diode temperature accuracy will be

trimmed for the thermal diode of a Prescott processor and

the accuracy will be guaranteed only when using this diode.

Diode fault detection circuitry in the LM95221 can detect the

presence of a remote diode: whether D+ is shorted to V

D- or ground, or whether D+ is floating.

The LM95221 register set has an 8-bit data structure and

includes:

1.

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

ter

2.

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

ter

3.

MSB Remote Temperature 1 Register

4.

LSB Remote Temperature 1 Register

5.

MSB Remote Temperature 2 Register

6.

LSB Remote Temperature 2 Register

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