VTM48Ex040y050B0R  
					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.  
					Using the Control Signals VC, PC, TM, IM  
					The VTM Control (VC) pin is a primary referenced 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 primary is  
					below 26V. In order to ensure a proper start, the slew rate of the  
					applied voltage must be within the specified range.  
					Start Up Behavior  
					Depending on the sequencing of the VC voltage with respect  
					to the same voltage, whether the source is on the primary or  
					secondary, the behavior during start up will vary as follows:  
					Some additional notes on the using the VC pin:  
					nꢀIn most applications, the VTM module primary side 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.  
					nꢀNormal operation (VC applied prior to the source voltage):  
					In this case, the controller is active prior to the source  
					ramping. When the source voltage is applied, the VTM  
					module load voltage will track the source (See Figure 13).  
					The inrush current is determined by the source voltage rate  
					of rise and load capacitance. If the VC voltage is removed  
					prior to the primary voltage reaching 26V, the VTM may  
					shut down.  
					nꢀIn bi-directional applications, the primary of the VTM may  
					also be providing power to a PRM input. In these  
					applications, a proper VC voltage within the specified range  
					must be applied any time the primary voltage of the VTM is  
					below 26V.  
					nꢀStand-alone operation (VC applied after VPRI): In this case the  
					VTM secondary will begin to rise upon the application of the  
					VC voltage (See Figure 14). The Adaptive Soft Start Circuit may  
					vary the secondary voltage rate of rise in order to limit the inrush  
					current to its maximum level. When starting into high  
					capacitance, or a short, the secondary 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 secondary capacitance is limited to 9100µF in this  
					mode of operation to ensure a successful start.  
					nꢀThe VC voltage can be applied indefinitely allowing for  
					continuous operation down to 0VPRI  
					.
					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) is a primary referenced pin that can be used  
					to accomplish the following functions:  
					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.  
					Thermal Considerations  
					VI Chip® products are multi-chip modules whose temperature  
					distribution varies greatly for each part number as well as with  
					the line/load conditions, thermal management and environmental  
					conditions. Maintaining the top of the VTM48EF040T050B0R 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.  
					nꢀDisable: PC pin can be actively pulled down in order  
					to disable the module. Pull down impedance shall be lower  
					than 400Ω.  
					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 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.  
					nꢀFault reset: PC may be toggled to restart the unit if VC  
					It is not recommended to use a VI Chip module for an extended  
					period of time at full load without proper heat sinking.  
					is continuously applied.  
					Temperature Monitor (TM) is a primary referenced pin that  
					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.  
					VTM™ Current Multiplier  
					Page 13 of 21  
					Rev 1.3  
					11/2016  
					vicorpower.com  
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