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ACT4910QW データシート(PDF) 23 Page - Active-Semi, Inc |
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ACT4910QW データシート(HTML) 23 Page - Active-Semi, Inc |
23 / 34 page ACT4910QW Rev 1.0, 15-Sept-2017 Innovative PowerTM www.active-semi.com ActiveSwitcherTM is a trademark of Active-Semi Copyright © 2017 Active-Semi, Inc. 23 Where Vripple is the desired output ripple voltage, FSW is the switching frequency in Hz, and ΔIL is the maximum ripple current in Amperes. As with the input capacitor selection, use X5R or X7R dielectrics and be sure to consider the capacitor’s DC bias effects. Storage Boost Converter General Description The ACT4910 contains an integrated peak current- mode, synchronous boost converter. It minimizes system level costs by using the same components as the buck converter. The peak current is adjustable between 250mA and 950mA, allowing for system optimization. The output voltage is adjustable between 5V and 36V via I2C registers and an external resistor. The peak current-mode control topology eliminates the need for compensation. The boost automatically charges up the storage capacitors from the input voltage so they are ready to provide backup power in the event of a system fault. Startup The boost converter automatically starts when the IC exits the SOFTSTART state. Note that the IC exits the SOFTSTART state 10ms after the output voltage is within 200mV of the input voltage. When the storage voltage reaches regulation, the boost enters standby mode and monitors the storage voltage. It automatically turns back on and “tops off” the storage capacitors when the storage voltage drops below 95% of the programmed voltage. The boost converter automatically turns off if it is “topping off” the storage capacitors when the IC enters supplement mode. The average input current when the boost charges the storage capacitors is approximately ½ of the peak switching current. The peak switch current is programed by register BST_CLIM[1:0]. Table 4: Boost Peak Current Settings BST_CLIM[1:0] (mA) 00 250 01 650 10 950 11 1500 Operating Mode The boost converter operates in peak current mode, non-fixed frequency mode. The power FET stays on until its current reaches programmed peak current. It then turns off until the inductor current drops to 0A, at which time it turns on again. Storage Capacitor Voltage Setting The buck converter output voltage is set by either the I2C register BSTVSET[4:0], or a combination the register and a resistor placed between the BSET pin to VSS. When using only the BSTVSET[4:0] leave the BSET pin floating. Table 5 shows the programmed storage voltage. The default value is determined by the IC’s specific CMI option. Table5: Storage Capacitor Voltage Settings with BSET Pin Open BSTVSET[3:0] BSTVSET[4] 0 1 0000 5V 21V 0001 5.6V 22V 0010 7V 23V 0011 8V 24V 0100 9V 25V 0101 10V 26V 0110 11V 27V 0111 12V 28V 1000 13V 29V 1001 14V 30V 1010 15V 31V 1011 16V 32V 1100 17V 33V 1101 18V 34V 1110 19V 35V 1111 20V 36V Using both the BSTVSET[4:0] register and an external resistor provides additional output voltage resolution. In this configuration, the following equation calculates the output voltage. ∗ Ω Equation 8 Where VBSTVSET is the voltage set by the BSTVSET register in Table 5 and RBSET is the resistor on the BSET pin in ohms. |
同様の部品番号 - ACT4910QW |
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同様の説明 - ACT4910QW |
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