QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC1059A TM DUAL IDEAL DIODE POWERPATH DEMOBOARD LTC4416 DESCRIPTION TM WARNING: READ THIS MANUAL FIRST BEFORE Demonstration circuit DC1059A is a dual PowerPath OPERATING THE DEMOBOARD. THERE ARE ILLEGAL circuit featuring the LTC4416. With the PFETs installed POWER CONFIGURATIONS OR VOLTAGE LEVELS THAT at the factory, the operational input voltage is 5 to 36V. CAN POTENTIALLY DAMAGE THE DEMOBOARD. The maximum charge current is 7A. The factory con- figuration features the standard LTC4416 setup for From the factory: Power Diode-Or and load sharing of two input power 1) MINIMUM INPUT VOLTAGE: The installed P- supplies assuming they both have identical ratings. It MOSFETS, SI7463DP have a minimum rated 4.5Vgs- can be quickly converted to other configurations on. Operating any FET below it minimum Vgs-on rating Although the board works as is, to get the most per- at any time can result in destruction of the FET. The formance out of the Demoboard, one FIRST needs to FETs are on the bottom of the board. determine what correct configuration you need for target 2) CONFIGURATION: Only the FETs blocking reverse applications. Some configurations may require user current flow, Q5 and Q7, are operational. If one acti- modification to the board prior to testing. Whatever vates the Off feature, which ever FET is turned off, will configuration you chose, you must understand the limits still pass forward current to the load via the FETs in- of that configuration. Refer to the schematic for more ternal parasitic diode. If the load current is high information. enough and passes through the FET that is turned off, Design files for this circuit board are available. Call the FET may burn up. the LTC factory. Table 1. Demoboard Performance Summary PARAMETER CONDITION/NOTES VALUE Maximum Input Voltage Derating relative to Absolute max of 40V. +36V Recommended Minimum Input Voltage Limited by Vgs rating of the installed PFET. 4.5V, 5V recommended. Reverse Input Stand-Off Voltage -14V Maximum. Maximum Current Limited by PFET Rds versus Pd rating of the De- 7A moboard. Shutdown Configuration. Id rating of installed SI7463DP PFET (Max) See PFET datasheet for most up to date information. 15A -4.5Vgs 18.6A -10Vgs Typical Forward Voltage Regulation (Vfd) See LTC4416 for complete information. 25mV (not guaranteed) Rds-on of installed SI7463DP PFET (Max) See PFET datasheet for most up to date information. 0.014 Ohms -4.5Vgs, 0.0092 Ohms -10Vgs Estimated actual Rds-on with Vin > 10V. Using SI7463DP PFET. Typical data. 0.008 Ohms -8Vgs Current level where Rds x I load > Vfd, 1 FET Using 25mV Vfd. 1 FET always on configuration. 3A Current level where Rds x I load > Vfd, 2 FET Using 25mV Vfd. 2 FET shutdown configuration. 1.5A 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC1059A TM DUAL IDEAL DIODE POWERPATH DEMOBOARD Changing the Default Configuration: The demo board has been configured as a dual Ideal-diode Power-Or Circuit with no shutoff capability by default. However a jumper, JMP5/6, is provided for each path such that if removed, will enable a second installed FET to be- come operational and allow shutdown capability for that path. Only in this mode can the On/Off control jumper be used safely under all load conditions. FET Package Options: The installed FETs are located on the bottom side of the Demoboard. The PCB footprint is compatible with standard SO-8 and Power SO-8 packages. Unstuffed PCB footprints supporting DD or TO-263 package are located on the top. This was done to permit airflow and/or heat-sinking as required for these bigger FETs. If you install the TO-263 part on the top, you should remove any and all FETs on the bottom. Only have the number of FETs you really need in- stalled. FET Types Supported: Any FET you chose must be a P-Channel MOSFET. There are no charge pumps to support N-Channel MOSFETs. See the datasheet for more information about FETs. Optimizing Factory Default Configuration: If you plan to never shut off a given power path, you should remove Q6 or Q8 in that path and leave JMP6 or JMP 5 installed respectively. If you never plan to shutoff any path, remove both Q6 and Q8 and leave both JMP5/6 installed. Removing the unused FET will speed up the response of the path in terms of it implementing the Idea diode function. See speed optimization section. PowerPath Shutdown Configuration: If you wish to enable shutdown of one or both paths, simply remove JMP5/6 as needed to activate the second FETs. Speed Optimization: Adding or leaving any un-necessary FETs installed will slow down the response time to less than what you will get in the real application. The gate drive is in the form of a current sink/source. Speed will be a function of the total Qg of all the FETs seen by the gate driver. Higher Qg gives slower response. Likewise lower Qg will result in faster re- sponse. For a given stated of FET technology, higher Qg FETs offer lower Rds-on while lower Qg FETs have higher Rds-on. Thus there is tradeoff between speed and Rds-on. If the voltages being managed by the LTC4416 are fast in coming or going, speed may be more important than Rds-on. Installing a LTC4416-1: This board will support an LTC4416-1 if you replace the supplied LTC4416. The LTC4416-1 offers a Fast-Off feature that is often more suitable when the two supplies rails are NOT going to share the load current. 2