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XC9509K Datasheet(PDF) 7 Page - Torex Semiconductor |
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XC9509K Datasheet(HTML) 7 Page - Torex Semiconductor |
7 / 9 page Synchronous Step-Down DC/DC Converter with Built-In LDO Regulator in Parallel plus Voltage Detector " TYPICAL APPLICATION CIRCUIT CIN : 4.7 µF (ceramic, TAIYO-YUDEN) CL1 : 10 µF (ceramic, TAIYO-YUDEN) CL2 : 1 µF (ceramic, TAIYO-YUDEN), VROUT>1.5V : 2.2 µF (ceramic, TAIYO-YUDEN), VROUT<1.5V " OPERATIONAL EXPLANATION % DC/DC Converter < Reference Voltage Source > The reference voltage source provides the reference voltage to ensure stable output voltage of the DC/DC converter. < Ramp Wave Circuit > < Error Amplifier > < PWM/PFM > XC9509 Series L The XC9509 series consists of a synchronous step-down DC/DC converter, a high speed LDO voltage regulator, and a voltage detector. FOSC 4.7 µH (CDRH4D28C, SUMIDA) 10 µH (CDRH4D28C, SUMIDA) 22 µH (CDRH4D28C, SUMIDA) 1.2MHz 600kHz 300kHz The error amplifier is designed to monitor output voltage. The amplifier compares the reference voltage with the feedback voltage divided by the internal split resistors. When a voltage lower than the reference voltage is fed back, the output voltage of the error amplifier increases. The gain and frequency characteristics of the error amplifier output are fixed internally to deliver an optimized signal to the mixer. The ramp wave circuit determines switching frequency. The frequency is fixed internally and can be selected from 300kHz, 600 kHz and 1.2 MHz. Clock pulses generated in this circuit are used to produce ramp waveforms needed for PWM operation, and to synchronize all the internal circuits. MSOP-10 (TOP VIEW) The series consists of a reference voltage source, ramp wave circuit, error amplifier, PWM comparator, phase compensation circuit, output voltage adjustment resistors, driver transistor, synchronous switch, current limiter circuit, U.V.L.O. circuit and others. The series ICs compare, using the error amplifier, the voltage of the internal voltage reference source with the feedback voltage from the VOUT pin through split resistors. Phase compensation is performed on the resulting error amplifier output, to input a signal to the PWM comparator to determine the turn-on time during PWM operation. The PWM comparator compares, in terms of voltage level, the signal from the error amplifier with the ramp wave from the ramp wave circuit, and delivers the resulting output to the buffer driver circuit to cause the Lx pin to output a switching duty cycle. This process is continuously performed to ensure stable output voltage. The current feedback circuit monitors the P-channel MOS driver transistor current for each switching operation, and modulates the error amplifier output signal to provide multiple feedback signals. This enables a stable feedback loop even when a low ESR capacitor, such as a ceramic capacitor, is used, ensuring stable output voltage. The PWM mode of the XC9509A to F series are controlled on a specified frequency from light loads through the heavy loads. Since the frequency is specified, the composition of a noise filter etc. becomes easy. However, the efficiency at the time of the light load may become low. The XC9509H to L series can switch in any timing between PWM control and PWM/PFM automatic switching control. The series can not control only PFM mode. If needed, the operation can be set on a specified frequency; therefore, the control of the noise etc. is possible and the high efficiency at the time of the light load during PFM control mode is possible. With the automatic PWM/PFM switching control function, the series ICs are automatically switched from PWM control to PFM control mode under light load conditions. If during light load conditions the coil current becomes discontinuous and on-time rate falls lower than 30%, the PFM circuit operates to output a pulse with 30% of a fixed on-time rate from the Lx pin. During PFM operation with this fixed on-time rate, pulses are generated at different frequencies according to conditions of the moment. This causes a reduction in the number of switching operations per unit of time, resulting in efficiency improvement under light load conditions. However, since pulse output frequency is not constant, consideration should be given if a noise filter or the like is needed. Necessary conditions for switching to PFM operation depend on input voltage, load current, coil value and other factors. Semiconductor Ltd. LX DCOUT VROUT MODE AGND PGND CE PVDD AVDD 1 CL2 L CL1 SD 2 3 4 5 6 7 8 9 10 CIN2 VDOUT VROUT DCOUT CIN1 Data Sheet 7 |
Similar Part No. - XC9509K |
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Similar Description - XC9509K |
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