TPS2340A

SLUS528A – MARCH 2002 – REVISED AUGUST 2002

13

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APPLICATION INFORMATION

fault handling

When PGOOD is asserted (main power is valid), the serial interface is available for use. At this time, Auxflt and

Faultx (i.e. Faultx = Pwrfltx

• Auxflt) signals are present in the registers and can be read back over the serial

interface.

When PGOOD is deasserted (main power is not valid), the serial interface is inactive, so the TPS2340A provides

an alternate path for observing the Auxfltx signals. In this case, Auxfltx is presented on the ATTLEDx open-drain

output, so 3Vaux faults can be observed. Systems that do not require Auxfltx indications when main power is

off should use main power to supply current to the attention LEDs.

In addition, when TEST is asserted after PGOOD has changed from 0 to 1, the AND of Pwrfltx and Auxfltx is

present on the ATTLEDx open-drain output, so the attention LEDs can be used to report any faults on each

channel.

follows the fault status of the main power fault (Pwrfltx).

Table 1. Fault Reporting Using ATTLED

SWx

PGOOD

TEST

ATTLEDx

< VDIGVCC

0

x

Auxfltx

< VDIGVCC

1

1

Pwrfltx

• Auxfltx

> VDIGVCC, < VV5IN

1

0

Pwrfltx

= VV5IN

x

x

Pwrfltx

PCI–XCAP resolution

Add-in cards indicate their PCI-X mode and frequency capabilities by connection of the PCI-XCAP pin. The

TPS2340A utilizes a three-level comparator to resolve the PCI-XCAP input so as to decode operating mode

and generate the PCI-XCAP2 and PCI-XCAP1 internal signals. With PCI-XCAP open, the TPS2340A selects

PCI-X 133-MHz operation. PCI-X 66-MHz operation is selected by a 10-k

Ω pull-down resistor on PCI-XCAP.

With PCI-XCAP grounded, conventional PCI-2.2 operation is selected. This decoding conforms to the standard

PCI-X specification for PCI-XCAP resolution.

Table 2. PCI-XCAP Pin State Resolution

PCI-XCAP

PCI-XCAP2

PCI-XCAP1

DESCRIPTION

GND

0

0

Conventional PCI 2.2 operation

10-k

Ω Pull-down Resistor

0

1

PCI-X 66-MHz operation

Open Circuit

1

1

PCI-X 133-MHz operation