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RT9619A Datasheet(PDF) 10 Page - Richtek Technology Corporation |
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RT9619A Datasheet(HTML) 10 Page - Richtek Technology Corporation |
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10 / 11 page  RT9619/A 10 DS9619/A-06 April 2011 www.richtek.com Layout Consideration Figure 5 shows the schematic circuit of a two-phase synchronous buck converter to implement the RT9619/A. The converter operates from 5V to 12V of VIN. When layout the PCB, it should be very careful. The power- circuit section is the most critical one. If not configured properly, it will generate a large amount of EMI. The junction of Q1, Q2, L2 should be very close. Next, the trace from UGATE, and LGATE should also be short to decrease the noise of the driver output signals. PHASE signals from the junction of the power MOSFET, carrying the large gate drive current pulses, should be as heavy as the gate drive trace. The bypass capacitor C4 should be connected to PGND directly. Furthermore, the bootstrap capacitors (CB) should always be placed as close to the pins of the IC as possible. VCC VIN PGND BOOT UGATE PHASE LGATE RT9619/A 1uF C L 3nF 20 C U 3nF 2N7002 2N7002 +12V +12V 1uF PWM 1N4148 C BOOT 10 0 100 200 300 400 500 600 700 800 900 1000 0 200 400 600 800 1000 Frequency (kHz) CU=CL=3nF CU=CL=1nF CU=CL=2nF Power Dissipation vs. Frequency The operating junction temperature can be calculated from the power dissipation curves (Figure 4). Assume VCC=12V, operating frequency is 200kHz and the CU=CL=1nF which emulate the input capacitances of the high side and low side power MOSFETs. From Figure 4, the power dissipation is 100mW. For RT9619/A, the package thermal resistance θJA is 160°C/W, the operating junction temperature is calculated as : Figure 3. Test Circuit This dissipation is a function of switching frequency and total gate charge of the selected MOSFET. Figure 3 shows the power dissipation test circuit. CL and CU are the UGATE and LGATE load capacitors, respectively. The bootstrap capacitor value is 1 μF. Figure 4 shows the power dissipation of the RT9619/A as a function of frequency and load capacitance. The value of the CU and CL are the same and the frequency is varied from 100kHz to 1MHz. Figure 4. Power Dissipation vs. Frequency TJ = (160 °C/W x 100mW) + 25°C = 41°C (11) where the ambient temperature is 25 °C. The method to improve the thermal transfer is to increase the PCB copper area around the RT9619/A first. Then, adding a ground pad under IC to transfer the heat to the peripheral of the board. Figure 5. Two-Phase Synchronous Buck Converter Circuit BOOT UGATE PHASE LGATE VCC VIN 14 2 5 7 8 PGND 10 1uF 12V 1uF PHB83N03LT PHB95N03LT 2uH 1uF 1000uF 1.2uH 12V 1500uF 6 L1 C1 L2 C3 Q2 Q1 C2 CB D1 R1 C4 PWM V IN V CORE |
Similar Part No. - RT9619A |
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Similar Description - RT9619A |
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