9.1.1.7.1 Current Sharing and TurboTrans™

When using TurboTrans while paralleling two modules, the TurboTrans resistor, R_TT, must be connected from the TurboTrans pin (pin 19) of the Master module to the +Sense pin (pin 17) of the Master module. When paralleling modules the procedure to calculate the proper value of output capacitance and R_TT is similar to that explained in the section, however the values must be calculated for a single module. Therefore, the total output current load step must be halved before determining the required output capacitance and the R_TT value as explained in the section. The value of output capacitance calculated is the minimum required output capacitance per module and the value of R_TT must be calculated using this value of output capacitance. The TurboTrans pin of the Slave module must be left open.

As an example, take a look at a 12-V application requiring a 60 mV deviation during an 30 A load transient. A majority of 470 μF, 10 mΩ output capacitors are used. Use the 12 V, Type B capacitor chart, Figure 15. First, halving the load transient gives 15 A. Dividing 60 mV by 15 A gives 4 mV/A transient voltage deviation per amp of transient load step. Select 4 mV/A on the Y-axis and read across to the 'With TurboTrans' plot. Following this point down to the X-axis gives us a minimum required output capacitance of approximately 1500 μF. This is the minimum required output capacitance per module. Hence, the total minimum output capacitance is 2 × 1500 μF = 3000 μF. The required R_TT resistor value for 1500 μF can then be calculated or selected from Table 5. The required R_TT resistor is approximately 17.4 kΩ.