Logic Design for Array-Based Circuits

by Donnamaie E. White

Copyright © 1996, 2001, 2002 Donnamaie E. White

 

Power Considerations

Last Edit July 22, 2001


Step 4: Compute the Total Typical Internal Macro Current

The macro current for individual internal macros is multiplied by the number of occurrences to determine the total for the use of that macro in the circuit. Change the labels if power has been specified

Compute the total current used by all occurrences of each internal macro and sum these totals to find:

    IinternalEE = SUM INTERNAL MACROS IEE CURRENT
    IinternalCC = SUM INTERNAL MACROS ICC CURRENT

Unless the circuit uses a single-power supply these two sums must be kept separate

Step 5: Compute the Worst-Case Internal Current

Multiply both sums by the worst-case current multiplier for the internal macros (WCCM2) to obtain the worst-case current due to interface macros

    IinternalCCwc = WCCM2 * IinternalCC
    IinternalEEwc = WCCM2 * IinternalEE

Step 6: Compute the Total Typical Overhead Current

Compute the total overhead current used by the circuit

    IoverheadEE = Table entry for array and I/O mode
    IoverheadCC = Table entry for array and I/O mode

Unless the circuit uses a single-power supply these two terms must be kept separate.

The vendor may specify a computation based on number of inputs or outputs of a given type. AMCC specifies a typical overhead current by array, by I/O mode (ECL-TTL or mixed) and power supply

Note: The DECL and the mixed ECL/TTL dual supply arrays dissipate the same overhead current. In the case of the DECL circuit, some of the ma-cros that require the use of two power supplies will dissipate an ICC current component

Table 7-13 Q20000 Series Example Typical Overhead Currents

ARRAY ECL Mode
IEE, mA
ECL Mode
"DECL"
Dual Supply
IEE/ICC, mA
ECL/TTL
Mixed Mode
IEE/ICC, mA
Q20160 400 400/40 400/40
Q20080 180 180/26 180/26
Q20045 126 126/26 126/26
Q20025 126 126/26 126/26
Q20010 67 67/13 67/13

 

Copyright @ 2001, 2002 Donnamaie E. White, White Enterprises
For problems or questions on these pages, contact dew@Donnamaie.com

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