VTM48Ex096y025A00  
					Using the control signals VC, PC, TM, IM  
					Start Up Behavior  
					The VTM Control (VC) pin is an input pin which powers the  
					internal VCC circuitry when within the specified voltage range of  
					11.5V to 16.5V. This voltage is required for VTM current multiplier  
					start up and must be applied as long as the input is below 26V.  
					In order to ensure a proper start, the slew rate of the applied  
					voltage must be within the specified range.  
					Depending on the sequencing of the VC with respect to the input  
					voltage, the behavior during start up will vary as follows:  
					nꢀNormal operation (VC applied prior to VIN): In this case the  
					controller is active prior to ramping the input. When the  
					input voltage is applied, the VTM module output voltage will  
					track the input (See Figure 13). The inrush current is  
					determined by the input voltage rate of rise and output  
					capacitance. If the VC voltage is removed prior to the input  
					reaching 26V, the VTM may shut down.  
					Some additional notes on the using the VC pin:  
					nꢀIn most applications, the VTM module will be powered by  
					an upstream PRM™ regulator which provides a 10ms VC  
					pulse during start up. In these applications the VC pins of  
					the PRM regulator and VTM current multiplier should be  
					tied together.  
					nꢀStand-alone operation (VC applied after VIN): In this case the  
					VTM output will begin to rise upon the application of the  
					VC voltage (See Figure 14). The Adaptive Soft Start Circuit  
					may vary the output rate of rise in order to limit the  
					inrush current to its maximum level. When starting into high  
					capacitance, or a short, the output current will be limited for  
					a maximum of 1200µs. After this period, the Adaptive Soft  
					Start Circuit will time out and the VTM module may shut  
					down. No restart will be attempted until VC is re-applied or PC  
					is toggled. The maximum output capacitance is limited to  
					1600µF in this mode of operation to ensure a sucessful start.  
					nꢀThe VC voltage can be applied indefinitely allowing for  
					continuous operation down to 0VIN.  
					nꢀThe fault response of the VTM module is latching. A positive  
					edge on VC is required in order to restart the unit. If VC is  
					continuously applied the PC pin may be toggled to restart  
					the VTM module.  
					Primary Control (PC) pin can be used to accomplish the  
					following functions:  
					Thermal Considerations  
					nꢀDelayed start: Upon the application of VC, the PC pin will  
					source a constant 100µA current to the internal RC  
					network. Adding an external capacitor will allow further  
					delay in reaching the 2.5V threshold for module start.  
					VI Chip® products are multi-chip modules whose temperature  
					distribution varies greatly for each part number as well as with the  
					input/output conditions, thermal management and environmental  
					conditions. Maintaining the top of the VTM48EF096T025A00  
					case to less than 100ºC will keep all junctions within the VI Chip  
					module below 125ºC for most applications.  
					nꢀAuxiliary voltage source: Once enabled in regular  
					operational conditions (no fault), each VTM PC provides a  
					regulated 5V, 2mA voltage source.  
					The percent of total heat dissipated through the top surface  
					versus through the J-lead is entirely dependent on the particular  
					mechanical and thermal environment. The heat dissipated  
					through the top surface is typically 60%. The heat  
					nꢀOutput disable: PC pin can be actively pulled down in order  
					to disable the module. Pull down impedance shall be lower  
					than 400Ω.  
					dissipated through the J-lead onto the PCB board surface is  
					typically 40%. Use 100% top surface dissipation when designing  
					for a conservative cooling solution.  
					nꢀFault detection flag: The PC 5V voltage source is internally  
					turned off as soon as a fault is detected. It is important to  
					notice that PC doesn’t have current sink capability. Therefore,  
					in an array, PC line will not be capable of disabling  
					neighboring modules if a fault is detected.  
					It is not recommended to use a VI Chip module for an extended  
					period of time at full load without proper heat sinking.  
					nꢀFault reset: PC may be toggled to restart the unit if VC  
					is continuously applied.  
					Temperature Monitor (TM) pin provides a voltage proportional  
					to the absolute temperature of the converter control IC.  
					It can be used to accomplish the following functions:  
					nꢀMonitor the control IC temperature: The temperature in  
					Kelvin is equal to the voltage on the TM pin scaled  
					by 100. (i.e. 3.0V = 300K = 27ºC). If a heat sink is applied,  
					TM can be used to thermally protect the system.  
					nꢀFault detection flag: The TM voltage source is internally  
					turned off as soon as a fault is detected. For system  
					monitoring purposes (microcontroller interface) faults are  
					detected on falling edges of TM signal.  
					VTM™ Current Mulitplier  
					Page 11 of 19  
					Rev 1.3  
					09/2016  
					vicorpower.com  
					800 927.9474