The bipolar array may have internal current limits that need to be honored. Drivers reduce the number of other macros that would be required but their use may increase the overall power required by the circuit. For some bipolar interface macros, as defined in the macro library documentation, the current is state-dependent. The ICC and IEE values for many of the interface macros are specified for HIGH and LOW input. For those arrays with placement-dependent overhead current, the knowledge that a designer might influence power by careful placement is dangerous.
Placement is driven by speed performance requirements and array placement restrictions.
The AMCC Q24000B BiCMOS array has placement-dependent overhead current. The numbers are the same for an ECL 100K array, whether or not both ECL 10K and ECL 100K outputs are used. There will be some variation in the complexity of the steps between vendors, depending on the method used to specify current or power dissipation for individual macros. The following example methodology assumes that typical current is specified. Keep IEE and ICC separate Sum all individual internal macro currents and multiply by the internal macro worst-case current multiplier.