Analog Devices LT8645SA | Demoboard EVAL-LT8645SA-AZ

Beschreibung

The evaluation circuit EVAL-LT8645SA-AZ is a 65V, 8A synchronous step-down second generation Silent Switcher® with spread spectrum frequency modulation featuring the LT8645SA. The evaluation board is designed for 5V output from a 5.6V to 65V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8645SA is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. The integrated bypass capacitors optimize all the fast current loops and make it easier to minimize EMI/EMC emissions by reducing layout sensitivity. Selectable spread spectrum mode can further improve EMI/EMC performance. Ultralow quiescent current in Burst Mode® operation achieves high efficiency at very light loads. Fast minimum on-time of 40ns enables high VIN to low VOUT conversion at high frequency.The LT8645SA switching frequency can be programmed either through oscillator resistor or external clock over a 200kHz to 2.2MHz range. The default frequency of EVAL-LT8645SA-AZ is 2MHz. The SYNC pin on the demo board is grounded (JP1 at BURST position) by default for low ripple Burst Mode operation. To synchronize to an external clock, move JP1 to SYNC and apply the external clock to the SYNC terminal. Select the spread spectrum mode and forced continuous mode (FCM), respectively, by moving the JP1 shunt. Figure 1 in the User Guide shows the efficiency of the circuit at 12V input and 24V input in Burst Mode operation (input from VIN terminal to bypass the EMI filter). Figure 2 shows the LT8645SA temperature rising on EVAL-LT8645SA-AZ board under different load conditions. The rated maximum load current is 8A, while derating is necessary for certain input voltage and thermal conditions. Low switching frequency can extend the output load capability by reducing the power dissipation. Figure 3 in the User Guide shows the temperature rising at 400kHz switching frequency.Please see the User Guide for the full description.

Eigenschaften

The evaluation circuit EVAL-LT8645SA-AZ is a 65V, 8Asynchronous step-down second generation SilentSwitcher® with spread spectrum frequency modulationfeaturing the LT8645SA. The evaluation board isdesigned for 5V output from a 5.6V to 65V input. Thewide input range allows a variety of input sources, suchas automotive batteries and industrial supplies. TheLT8645SA is a compact, ultralow emission, highefficiency, and high speed synchronous monolithicstep-down switching regulator. The integrated bypasscapacitors optimize all the fast current loops and makeit easier to minimize EMI/EMC emissions by reducinglayout sensitivity. Selectable spread spectrum modecan further improve EMI/EMC performance. Ultralowquiescent current in Burst Mode® operation achieveshigh efficiency at very light loads. Fast minimum on-timeof 40ns enables high VIN to low VOUT conversion at highfrequency.TheLT8645SA switching frequency can beprogrammed either through oscillator resistor orexternal clock over a 200kHz to 2.2MHz range. Thedefault frequency of EVAL-LT8645SA-AZ is 2MHz. TheSYNC pin on the demo board is grounded (JP1 atBURST position) by default for low ripple Burst Modeoperation. To synchronize to an external clock, moveJP1 to SYNC and apply the external clock to the SYNCterminal. Select the spread spectrum mode and forcedcontinuous mode (FCM), respectively, by moving theJP1 shunt. Figure 1 shows the efficiency of the circuit at12V input and 24V input in Burst Mode operation (inputfrom VIN terminal to bypass the EMI filter). Figure 2shows the LT8645SA temperature rising on EVALLT8645SA-AZ board under different load conditions.The rated maximum load current is 8A, while deratingis necessary for certain input voltage and thermalconditions. Low switching frequency can extend theoutput load capability by reducing the powerdissipation. Figure 3 shows the temperature rising at400kHz switching frequency.The evaluation board has an EMI filter installed.Figure 4 shows the EMI performance of the board (withEMI filter). The red line in conducted and radiated EMIperformance is CISPR25 class 5 peak limit. The figureshows that the circuit passes the test with a widemargin. To achieve EMI/EMC performance, as shownin Figure 4, the input EMI filter is required, and the inputvoltage should be applied at the VEMI terminal. Aninductor can be added in the EMI filter to further reducethe conducted emission. The EMI filter can be bypassedby applying the input voltage at VIN terminal.The LT8645SA data sheet gives a complete descriptionof the part, operation and application information. Thedata sheet must be read in conjunction with this userguide for EVAL-LT8645SA-AZ. The LT8645SA isassembled in a 6mm x 4mm LQFN package withexposed pads for low thermal resistance. The layoutrecommendations for low EMI operation and maximumthermal performance are available in the data sheetsection Low EMI PCB Layout and ThermalConsiderations.

Typische Anwendungen

Weiterführende Informationen

• Datenblatt
• Produktseite des IC-Herstellers