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CT600-PX0624GM MCU, which has been factory-programmed to generate primary-side transformer switch timing. Figure 1. ISOvolt Isolated DC/DC Block Diagram voltage is regulated by a linear output regulator (U4). J1 and J2, and VOUT+ supplies bias to the output side of the isolator. volt Isolated DC-DC Converter Reference Design Users Guide”.
to 5.5 V dc; therefore, the gate drivers must provide a 0 to VIN output swing from a maximum input signal of 3.3 V. To meet this criterion, the discrete gate driver circuits use a bootstrap circuit to level-shift driver output swing. charges to approximately (VIN – 0.7 V). When the MCU outp ut transitions high, Q1 base is driven by Vboot (i.e. circuit (C5, R2) provides “speed-up” for Q2 (Channel 2, Figure 2). Figure 2. Bootstrap Driver Operation for transistor Q1. It also helps to keep the base of transistor pulled high till the microcontroller starts switching. normal value before the next switching cycle begins. conduction, which can lower efficiency or destroy the converter. The driver layout should be as tight as possible to minimize inductance.
Figure 3. Active Clamp selected for power dissipation.
6 Rev. 0.2 2. Adjusting Converter Performance The gate driver used in this reference design is a general -purpose driver that can be used to drive any high- and low-side drive with the proper selection of components. Th e selection of the bootstrap capacitor and resistor is important (see "1.1. Gate Driver Circuit s" on page 2 for details). Increasing the gate drive current requires higher current drive transistors (e.g. Q1 and Q2 in Figure 2). 2.1. Changing Output Voltage The dc-dc converter can be adapted for different output vo ltages by modifying the turns-ratio of the isolation transformer. The secondary rectifiers (diodes D1 and D2 shown in Figure 1) should be rated for at least twice the maximum clamped voltage at the input to the linear regulato r. In practice, it is recommended to use at least 50% overhead above this value to accommodate the voltage spikes due to circuit parasitics. The output filter capacitor should also be rated according to the maximum output voltage generated.
8 Rev. 0.2 DOCUMENT CHANGE LIST Revision 0.1 to Revision 0.2 Changed “Si8441” to “Si8641” throughout.
Rev. 0.2 9 NOTES:
Silicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products must not be used within any Life Support System without the specific written consent of Silicon Laboratories. A "Life Support System" is any product or system intended to support or sustain life and/or health, which, if it fails, can be reasonably expected to result in significant personal injury or death. Silicon Laboratories products are generally not intended for military applications. Silicon Laboratories products shall under no circumstances be used in weapons of mass destruction including (but not limited to) nuclear, biological or chemical weapons, or missiles capable of delivering such weapons. Trademark Information Silicon Laboratories Inc., Silicon Laboratories, Silicon Labs, SiLabs and the Silicon Labs logo, CMEMS®, EFM, EFM32, EFR, Energy Micro, Energy Micro logo and combinations thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZMac®, EZRadio®, EZRadioPRO®, DSPLL®, ISOmodem ®, Precision32®, ProSLIC®, SiPHY®, USBXpress® and others are trademarks or registered trademarks of Silicon Laboratories Inc. ARM, CORTEX, Cortex-M3 and THUMB are trademarks or registered trademarks of ARM Holdings. Keil is a registered trademark of ARM Limited. All other products or brand names mentioned herein are trademarks of their respective holders. http://www.silabs.com Silicon Laboratories Inc.
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