RE: [IBIS] Determining correct Junction temperature for IBIS models

Tom,

Good advice. I agree that the operating dissipation is key. The operating dissipation that I am quoting includes the I/O power dissipation and the rest of the chip; or the total power dissipation.

That being the case, would you recommend options 7, 8, 9, or 10 for the correct calculation?

Best Regards,

Bonnie Baker
Signal Integrity Engineer
Texas Instruments, Tucson

5411 E. Williams
Tucson, Arizona 85711

(520) 750-2116 (work)
(520) 548-3111 (cell)

From: Tom Dagostino [mailto:tom@teraspeed.com]
Sent: Sunday, June 26, 2011 2:58 PM
To: Baker, Bonnie; 'ibis@server.eda-stds.org'
Subject: RE: [IBIS] Determining correct Junction temperature for IBIS models

Bonnie

I think you should look at operating temperatures and ignore the quiescent dissipation. The part does not have SI characteristics if no real work is being done. Does your operating dissipation include the I/O drivers' power dissipation or just the chip. You really need to look at total dissipation.

Common practice is to use the actual die temperature at the conditions of operation.

Tom Dagostino

Teraspeed Labs
9999 SW Wilshire St.
Suite 102
Portland, OR 97225
USA

971-279-5325 Office
971-279-5326 FAX
503-430-1065 Cell

tom@teraspeed.com<mailto:tom@teraspeed.com>
www.teraspeed.com<http://www.teraspeed.com/>

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827

From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Baker, Bonnie
Sent: Sunday, June 26, 2011 2:23 PM
To: ibis@server.eda-stds.org
Subject: [IBIS] Determining correct Junction temperature for IBIS models

IBIS experts,

I am in the midst of creating numerous IBIS models for a wide variety of products. The issue that has come up is the selection of the proper junction temperature values for my 3 corners.

Given that the specified temperature for a device is -40 C to 85C.

Corner supplies are 4.5V, 5V, and 5.5V.

The package theta-ja 100 C/W.

The nominal room temperature quiescent power dissipation at 5V power supply voltage is 50 mW. theta-ja * 50mW = 5C

The nominal room temperature operating power dissipation at 5V power supply voltage is 100 mW. theta-ja * 100mW = 10C

The nominal cold power quiescent dissipation (@ -40C, 5V supply) is 40mW. theta-ja * 40mW = 4C

The nominal cold power operating dissipation (@ -40C, 5V supply) is 80mW. theta-ja * 80mW = 8C

The nominal hot power quiescent dissipation (@ 85C, 5V supply) is 60mW. theta-ja * 60mW = 6C

The nominal hot power operating dissipation (@ 85C, 5V supply) is 120mW. theta-ja * 120mW = 12C

Which option is correct?

Option 1: Create IBIS model with

-40C, 25C, and 85C temperatures

Option 2: Calculate nominal quiescent room temperature power dissipation and multiply that times the package theta-ja. Add this delta temperature to all three temperatures. In this case the IBIS temperatures are

-35C, 30C, and 90C.

Option 3: Calculate nominal quiescent room temperature power dissipation and multiply that times the package theta-ja. Add this delta temperature to the two higher temperatures. In this case the IBIS temperatures are

-40C, 30C, and 90C.

Option 4: Calculate the quiescent power dissipation at all temperatures and multiply that times theta-ja. The IBIS temperatures in this case would be

-36C, 30C, and 91C.

Option 5: Apply the mathematics of quiescent power and theta-ja to the two higher temperatures. In this case the IBIS temperatures are

-40C, 30C, and 91C.

Option 7: Apply Option 2 to operating power dissipation conditions. In this case the IBIS temperatures are

-30C, 35C, and 95C.

Option 8: Apply Option 3 to operating power dissipation conditions. In this case the IBIS temperatures are

-40C, 35C, and 95C.

Option 9: Apply Option 4 to operating power dissipation conditions. In this case the IBIS temperatures are

-32C, 35C, and 97C.

Option 10: Apply Option 5 to operating power dissipation conditions. In this case the IBIS temperatures are

-40C, 35C, and 97C.

Option 11: Add 15 deg C to -40C, 25C, and 85C or create IBIS model with

-25C, 40C, and 100C.

Option 12: Add 15 deg C to 25C and 85C or create IBIS model with

-40C, 40C, and 100C.

Bonnie

--
This message has been scanned for viruses and
dangerous content by MailScanner<http://www.mailscanner.info/>, and is
believed to be clean.
-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
--------------------------------------------------------------------
|For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org
|with the appropriate command message(s) in the body:
|
|  help
|  subscribe   ibis       <optional e-mail address, if different>
|  subscribe   ibis-users <optional e-mail address, if different>
|  unsubscribe ibis       <optional e-mail address, if different>
|  unsubscribe ibis-users <optional e-mail address, if different>
|
|or e-mail a request to ibis-request@eda-stds.org.
|
|IBIS reflector archives exist under:
|
|  http://www.eda-stds.org/pub/ibis/email_archive/ Recent
|  http://www.eda-stds.org/pub/ibis/users_archive/ Recent
|  http://www.eda-stds.org/pub/ibis/email/         E-mail since 1993