Logic Design for Array-Based Circuits

Copyright © 1996, 2001, 2002, 2008, 2016 Donnamaie E. White, WhitePubs Enterprises, Inc.

• Table of Contents
  
• Preface
  
• Overview
  
• Chapter 1 Introduction
  
• Chapter 2 Structured Design Methodology
• Chapter 3 Sizing the Design
• Chapter 3 Appendix = Case Study in Sizing a Design
• Chapter 4 Design Optimization
• Chapter 5 Timing Analysis for Arrays
• Chapter 6 External Set-up and Hold Times
• Chapter 7 Power Considerations
• Case Study: DC Power Computation
  • Steps Required to Compute DC Power - Example Array Series
  • Build the Macro Occurence Table
  • Find the Tital Interface Macro Current
  • Computer the Worst-Case Interface Current
  • Compute the Total Typical Internal Macro Current
  • Compute the Worst-Case Internal Current
  • Compute the Total Typical Overhead Current
  • Compute the Worst-Case Overhead Current
  • Sum the ICC and IEE Currents
  • Multiply by Worst-Case Voltage
  • Determine ECL Static Power PEO
  • ECL Output Termination Current
  • Sum the Result - Total DC Power
  • Exercises
• Case Study: AC Power Computation
  • Build the Macro Occurrence Table
  • Find the Number of Darlington Outputs
  • Compute AC Power for all ECL Darlington Output Macros
  • Find the Number of ECL Inputs
  • Compute AM Power for all ECL Input Macros
  • Find the Number of Internal Macros
  • Compute AC Power for all Internal Macros
  • Sum All Components of AC Power
  • Total Power Dissipation
  • Exercises
• Chapter 8 Simulation
• Case Study: Simulation
• Chapter 9 Faults and Fault Detection
• Chapter 10 Design Submission
• ASIC Glossary
  • Glossary A-D
  • Glossary E-K
  • Glossary L-R
  • Glossary S-Z
  • Symbols

Power Considerations

Last Edit July 22, 2001

Step 10: Determine ECL Static Power PEO

The equation used by the AMCC MacroMatrix ERC software to compute ECL static power dissipation for ECL outputs is:

PEO = XXmA * 1.3V * NUMBER_OF_ECL_OUTPUTS

The 1.3V term represents the average between VOH and VOL. This is considered to be the statistical worst-case for this function

If there is more than one termination, the power for each type of termination is computed and summed to find the total PECL outputs

ECL Output Termination Current

Table 7-15 provides the ECL output termination currents used by the AMCC MacroMatrix ERC software. The currents shown are the average current (average of IOH and IOL)

AMCC automated ECL static power is computed with the 50 or 25 ohm termination under the assumption of 50% terminations active. This is because AMCC provides macros that drive 50 ohm loads and macros that drive 25 ohm loads. These assumptions may vary with the vendor.

Table 7-15 ECL Termination Current

* the average current (average of IOH and IOL) for termination to -2V

* When 50 ohm or 25 ohm Terminations are Not Used

Resistive loads that differ from that used by automation software will require manual computation. These loads should be identified when performing design submission to any vendor.

If other ECL output load resistances are used, the actual current value must be computed for use in the ECL static power equation. For a -2V termination, to find the average current in mA, use the following equation.

I in mA = 0.7/( R * (10-3)) for any R

* When VT Ê -2V

For other termination voltages, an adjustment to the power dissipation computation must be made by the designer. For a termination voltage VT, to find the average current in mA, use the following equation.

I in mA = (-1.3V - VT)/( R * (10-3)) for any R

* Darlington ECL Outputs

Darlington ECL outputs are treated as a standard ECL outputs for static power computations.

* On-Chip Series Termination

There is no IOEF output current for on-chip series termination ECL output macros. All current (power) dissipated is specified in the macro docu-mentation.

Step 11: Sum the Result - Total DC power

Sum the results of the macro and overhead current power computations with any ECL output macro static power dissipation to obtain the total worst-case DC power dissipation for the circuit:

PdDC = PCCDC + PEEDC + PEO

The result is the total worst-case DC power dissipated by the circuit on the target array.

Exercises

1. Determine how current or power is specified for an array series of interest. Is it worst-case? If not, find out how the data is converted to worst-case for Commercial and for Military operating conditions.

2. Determine how overhead current is accounted for by this array series. Is it variable? If so, determine what affects it, e.g., number of I/O by type or their placement.

3. What other adjustments are required before a final DC power value can be obtained? If the manual is not specific, consult the vendor.

4. AMCC Q20000 Exercise. A 100% ECL circuit has been designed using the Q20080 (8K) array. It uses the following example values:
   
   

   Macro Name:	Number Used:	Current: IEE mA
   FF10S	32	0.98
   FF46S	32	0.93
   GT09S	0	0.39
   GT55D	4	0.91
   GT60L	6	0.64
   GT60S	6	0.78
   GT87D	2	0.49
   IE31H	1	2.20
   IE93S	82	1.03
   IEVCC	9	0.00
   MX21S	20	0.66
   OE42S	69	8.72

   Typical current is specified for one occurrence of each macro. The power supply is nominal -5.2V. The circuit is military. Compute its DC power dissipation given the above portion of the macro occurrence table and the other tables provided in the text. [Ans.: 8.32 Watts (1994 data)]

5. Substitute 32 OE14S macros that use 6.69 mA each for 64 of the OE42S macros and delete one of the GT87D macros. Now how much power is dissipated?

Copyright © 1996, 2001, 2002, 2008, 2016 Donnamaie E. White , WhitePubs Enterprises, Inc.
For problems or questions on these pages, contact donnamaie@-no-spam-sbcglobal.net