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BA33D18HFP Datenblatt(PDF) 6 Page - Rohm |
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BA33D18HFP Datenblatt(HTML) 6 Page - Rohm |
6 / 9 page BA3258HFP, BA33D15HFP, BA33D18HFP Technical Note 6/8 www.rohm.co 2009.04 - Rev.A © 2009 ROHM Co., Ltd. All rights reserved. Thermal Design If the IC is used under excessive power dissipation conditions, the chip temperature will rise, which will have an adverse effect on the electrical characteristics of the IC, such as a reduction in current capability. Furthermore, if the temperature exceeds Tjmax, element deterioration or damage may occur. Implement proper thermal designs to ensure that the power dissipation is within the permissible range in order to prevent instantaneous IC damage resulting from heat and maintain the reliability of the IC for long-term operation. Refer to the power derating characteristics curves in Fig. 29. Power Consumption (Pc) Calculation Method Power consumption of 3.3V power transistor: Pc1 = (Vcc − 3.3) Io1 Power consumption of Vo2 power transistor: Pc2 = (Vcc − Vo2) Io2 Power consumption due to circuit current: Pc3 = Vcc Icc → Pc = Pc1 + Pc2 + Pc3 Refer to the above and implement proper thermal designs so that the IC will not be used under excessive power dissipation conditions under the entire operating temperature range. Calculation example (BA33D15HFP) Example: Vcc = 5V, Io1 = 200mA, and Io2 = 100mA Power consumption of 3.3V power transistor: Pc1 = (Vcc − 3.3) Io1 = (5 − 3.3) 0.2 = 0.34W Power consumption of 1.5V power transistor: Pc2 = (Vcc − 1.5) Io2 = (5 − 1.5) 0.2 = 0.35W Power consumption due to circuit current: Pc3 = Vcc Icc = 5 0.0085 = 0.0425 (W) (See Figs. 14 and 15) Implement proper thermal designs taking into consideration the dissipation at full power consumption (i.e., Pc1 + Pc2 + Pc3 = 0.34 + 0.35 + 0.0425 = 0.7325W). Explanation of External Components BA3258HFP 1) Pin 1 (Vcc pin) Connecting a ceramic capacitor with a capacitance of approximately 3.3 F between Vcc and GND as close to the pins as possible is recommended. 2) Pins 4 and 5 (Vo pins) Insert a capacitor between the Vo and GND pins in order to prevent output oscillation. The capacitor may oscillate if the capacitance changes as a result of temperature fluctuations. Therefore, it is recommended that a ceramic capacitor with a temperature coefficient of X5R or above and a maximum capacitance change (resulting from temperature fluctuations) of 10% be used. The capacitance should be between 1F and 1,000 F. (Refer to Fig. 30) BA33D□□ Series 1) Pin 1 (Vcc pin) Insert a 1 F capacitor between Vcc and GND. The capacitance will vary depending on the application. Check the capacitance with the application set and implement designing with a sufficient margin. 2) Pins 4 and 5 (Vo pins) Insert a capacitor between the Vo and GND pins in order to prevent oscillation. The capacitance may vary greatly with temperature changes, thus making it impossible to completely prevent oscillation. Therefore, use a tantalum aluminum electrolytic capacitor with a low ESR (Equivalent Serial Resistance). The output will oscillate if the ESR is too high or too low, so refer to the ESR characteristcs in Fig. 31 and operate the IC within the stable operating region. If there is a sudden load change, use a capacitor with higher capacitance. A capacitance between 10 F and 1,000 F is recommended. Fig. 29 Thermal Derating Curves Fig. 30 BA3258HFP ESR characteristics Fig. 31 BA33D□□ Series ESR AMBIENT TEMPERATURE:Ta[℃] 8 10 9 7 6 5 4 3 2 1 0 25 50 75 100 125 150 Board size: 70 mm 70 1.6 mm (with a thermal via incorporated by the board) Board surface area: 10.5 mm 10.5 mm (1) 2-layer board (Backside copper foil area: 15 mm 15mm) (2) 2-layer board (Backside copper foil area: 70 mm 70 mm) (3) 4-layer board (Backside copper foil area: 70 mm 70mm) 0 Io [mA] 200 400 600 800 1000 0 0.01 0.1 0.5 1.0 2.0 0.02 0.05 0.2 5.0 不安定領域 10.0 安定領域 0.15 4.0 不安定領域 200 400 600 800 1000 0 0.01 0.1 0.5 1.0 2.0 Io [mA] 安定領域 0.02 0.05 0.2 5.0 不安定領域 10.0 (3) 7.3 W (2) 5.5 W (1) 2.3 W *Vcc: Applied voltage Io1: Load current on Vo1 side Io2: Load current on Vo2 side Icc: Circuit current * The Icc (circuit current) varies with the load. (See reference data in Figs. 2, 3, 14, and 15.) Unstable region Unstable region Unstable region Stable region Stable region Vo1 Vo2 Controller 3.3 V output ower Vcc GND Vcc Vcc Power Tr Power Tr 1.5 V output or 1.8 V output I P Icc IO1 IO2 |
Ähnliche Teilenummer - BA33D18HFP |
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Ähnliche Beschreibung - BA33D18HFP |
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