The load-share bus driver is a unity-gain buffer amplifier to provide separation between the output of the current-sense amplifier and the load-share bus voltage. The circuit implements an ideal diode with virtually 0V forward voltage drop by placing the diode inside the feedback loop of the amplifier. The diode function is used to automatically establish the role of the leader module in the overall load-sharing system. In the system, the UCC29002 device that becomes the leader uses the load-share bus driver amplifier to drive its output-current information onto the load-share bus for all follower modules to emulate.

Assuming identical module design, any UCC29002 may assume the role of leader at any time depending on input and output conditions. Leadership is not fixed to one specific module. All follower modules will have lower output current levels by definition, and their ideal diodes are reversed biased (V_CSO < V_LS). Consequently, the follower V_CSO and V_LS signals will be separated. This separation allows the error amplifier of the follower UCC29002 device to compare its respective module output current to the output current of the leader module and make the necessary feedback-loop adjustments to achieve a balanced current distribution.

Because the LS bus is always driven by a single load-share bus driver (in the leader module), the total number of load-sharing modules (N_m) that may be connected to the LS bus is limited by the output-current capability of the leader's bus-driver amplifier according to Equation 1.

where

• I_OUT,MIN is the minimum limit of I_{OUT_LS} given in the Electrical Characteristics table.
• V_{LS,FULL_SCALE} is the maximum voltage on the LS bus at full load.
• 100kΩ is the input impedance of the LS pin as shown in the Functional Block Diagram.