LM93 datasheet(33/95 Pages) TI1

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DIODE TEMPERATURE (°C)

LM93

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SNAS210E – DECEMBER 2003 – REVISED MARCH 2013

Temperature errors are masked by writing a high temperature limit value of 80h. This is the default high

limit for all temperatures. Masking a temperature channel masks both temperature errors and diode fault

errors.

The GPI Mask register allows GPI errors to be masked. Any bits that are set in this register mask events

for the corresponding GPIO_x pin.

User PROCHOT status is not really an error but it can be used to notify the user of processor throttling

past a preset USER limit. A user limit of FFh acts as the mask for this register. Error bits associated with

the predefined PROCHOT thresholds cannot be masked. It is important to note though, that these error

bits do not cause BMC_ERR, HOST_ERR, or ALERT to be asserted under any condition.

Fan tach errors are masked if the tach limit for the given tach is set to FFh .

SCSI_TERMx errors and VRDx_HOT errors can be masked by setting the appropriate bit in the VRD

THERMTRIP and SCSI_TERM Error Mask register.

When the LM93 powers up, the ALERT output is disabled. The ALERT output can be enabled by setting

the ALERT_EN bit in the LM93 Configuration register.

In addition the manual masking options, the LM93 also masks some errors depending on the sleep state

of the system. The sleep state of the system is communicated to the LM93 by writing to the Sleep State

Control register. Some types of error events are always masked in certain sleep modes. Some types of

error events are optionally masked in certain sleep modes if their sleep mask register bit is set. Refer to

the Register Descriptions for more information.

3.16.8 LAYOUT AND GROUNDING

Analog components such as voltage dividers should be physically located as close as possible to the

LM93.

The LM93 bypass capacitors, the parallel combination of 100 pF, 10 µF (electrolytic or tantalum) and 0.1

µF (ceramic) bypass capacitors must be connected between power pin (pin 39) and ground, and should

be located as close as possible to the LM93. The 100 pF capacitor should be placed closest to the power

pin.

3.16.9 THERMAL DIODE APPLICATION

To measure temperature external to the LM93, we need to use a remote discrete diode to sense the

temperature of external objects or ambient air. Remember that the temperature of a discrete diode is

effected, and often dominated, by the temperature of its leads.

Most silicon diodes do not lend themselves well to this application. It is recommended that a MMBT3904

transistor type base emitter junction be used with the collector tied to the base.

Figure 3-3. Thermal Diode Temperature vs. LM93 Temperature Reading

Functional Description

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