LM93 datasheet(10/95 Pages) TI1

10 / 95 page

LM93

SNAS210E – DECEMBER 2003 – REVISED MARCH 2013

www.ti.com

SPACER

Zone

Description

Zone 1

Processor 1 remote diode

(REMOTE1+, REMOTE1

−)

Zone 2

Processor 2 remote diode

(REMOTE2+, REMOTE2

−)

Zone 3

Internal LM93 on-chip sensor

Zone 4

External Digital Sensor written in from SMBus

3.3.1

Temperature Data Format

Most of the temperature data for the LM93 is represented in a common format. The format is an 8-bit,

twos complement byte with the LSB equal to 1.0 °C. This applies to temperature measurements as well as

any temperature limit registers and some configuration registers. Some fan control configuration registers

use four bits and have a binary format, please see the Fan Control configuration register descriptions for

further details on this 4-bit format.

SPACER

Temperature(1)

Binary

Hex

+125°C

0111 1101

7Dh

+25°C

0001 1001

19h

+1.0°C

0000 0001

01h

0°C

0000 0000

00h

−1.0°C

1111 1111

FFh

−25°C

1110 0111

E7h

−55°C

1100 1001

C9h

−127°C

1000 0001

81h

(1)

Note: A value of 80h has a special meaning in the limit registers. It means that the temperature

channel is masked. In addition, temperature readings of 80h indicate thermal diode faults.

3.3.2

Thermal Diode Fault Status

The LM93 provides for indications of a fault (open or short circuit) with the remote thermal diodes. Before

a remote diode conversion is updated, the status of the remote diode is checked for an open or short

circuit condition. If such a fault condition occurs, a status bit is set in the status register. A short circuit is

defined as the input pins being connected to each other. When an open or short circuit is detected, the

corresponding temperature register is set to 80h.

3.4

VOLTAGE MONITORING

The LM93 contains inputs for monitoring voltages. Scaling is such that the correct value refers to

approximately 3/4 scale or 192 decimal on all inputs except the ±12V. Input voltages are converted by an

8-bit Delta-Sigma (

ΔΣ) A/D. The Delta-Sigma A/D architecture provides inherent filtering and spike

smoothing of the analog input signal.

The ±12V inputs must be scaled externally. A full scale reading is achieved when 1.236V is applied to

these inputs. For optimum performance the +12V should be scaled to provide a nominal ¾ full scale

reading, while the

−12V should be scaled to provide a nominal ¼ scale reading. The thevenin resistance

at the pin should be kept between 1 k

Ω and 7 kΩ.

Functional Description

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