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Motore di ricerca datesheet componenti elettronici |
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SP6650 Scheda tecnica(PDF) 14 Page - Sipex Corporation |
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SP6650 Scheda tecnica(HTML) 14 Page - Sipex Corporation |
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14 / 17 page  14 Date: 5/25/04 SP6650 High Efficiency 600mA Synchronous Buck Regulator © Copyright 2004 Sipex Corporation Figure 19. Additional Application Circuit: VIN = 5.0V, VOUT = 12V, and Max ILOAD = 150mA. RB 100k SP6650 U1 10 9 8 7 6 1 2 3 4 5 L3 47µH COUT1 100µF/16V R2 86k R3 10k PVIN VIN BLON ILIM SHDN LX PGND GND VOUT FB ® ® 12V/150mA VIN 4.5-6.5 VDC RVIN 5.0 R2 4.02k CIN 47µF D1 MBR0530TI Q1 FDS637AN R1 11.3k CVIN 1.0µF Figure 20. Additional Application Circuit: VIN= 5.0V, VOUT = 5.0V, ILOAD = 250mA. RB 100k SP6650 U1 10 9 8 7 6 1 2 3 4 5 L1 47µH COUT1 47µF R2 30.9k R3 10.2k PVIN VIN BLON ILIM SHDN LX PGND GND VOUT FB ® ® 5V/250mA VIN 4.5-6.5 VDC RVIN 10.0 R2 4.02k CIN 47µF D1 MBR0530T1 Q1 FDS637AN Cf2 470pF R1 11.3k CVIN 4.7µF COUT2 47µF SP6650 can also be configured with few external components to achieve buck-boost voltage con- version. Efficiency of 75% to 87% can often be obtained depending on the load current and output voltage. Figure 19 and Figure 20 demonstrate two typical applications in which the USB input is converted to a 12V and a well regulated 5V. The operation of the circuit is as follows. When the internal high side PMOS turns on, the LX pin swings to the input voltage which turns on the external NMOS Q1. A voltage equal to Vin is then applied to the inductor to cause the inductor current rise linearly. Since there’s no current delivered to the output, the output capacitor is discharged by the load current. Therefore, the internal PMOS can be only turned off by the over-current comparator since the loop com- parator would never toggle during this state. When the internal PMOS is open, the internal low side NMOS is turned on. This pulls the LX pin to the ground and turns off the Q1. As a ADDITIONAL APPLICATION CIRCUITS: continued result, the Schottky D2 is forward biased and conducts the inductor current to the output. Now the inductor experiences a reversed voltage equal to Vout and its current ramps down linearly. As expressed in the Operation section under In- ductor Over-Current Protection, a minimum TOFF timer is activated after the over-current comparator is triggered in the previous state. Before Toff expires, the internal PMOS will not turn on, and the inductor will not be recharged even when the output voltage drops below the regulation voltage. This reduces the maximum load current that can be delivered by this circuit. Since TOFF is reverse proportional to the VOUT pin voltage, the VOUT pin is pulled up using a voltage divider tying to the input voltage. As a result, a 5V to 12V conversion can provide maximum 120mA load. This buck-boost circuit can regulate an output voltage higher, lower or equal to the input voltage. |
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