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ADP5071ACPZ-R7 数据表(PDF) 15 Page - Analog Devices |
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ADP5071ACPZ-R7 数据表(HTML) 15 Page - Analog Devices |
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15 / 28 page  ADP5071 Data Sheet Rev. A | Page 14 of 27 THEORY OF OPERATION ERROR AMP + – INBK SWITCH CONTROL BOOST PWM CONTROL INBK SW1 VOUT1 FB1 COMP1 VIN CIN CURRENT SENSE PVIN1 SYNC/FREQ HV BAND GAP PGND SW2 FB2 INVERTER PWM CONTROL PVIN2 + – ERROR AMP HV REGULATOR EN1 EN2 PVINSYS VREG CVREG COMP2 SEQ SLEW SS AGND CURRENT SENSE START-UP TIMERS PLL 4µA REF1 REF2 REF1 REF2 SEQUENCE CONTROL OSCILLATOR SLEW SLEW BOOST_ENABLE INVERTER_ENABLE EN1 EN2 L1 D1 COUT1 RFT1 RFB1 RFT2 RFB2 L2 D2 COUT2 RC1 CC1 RC2 CC2 RSS (OPTIONAL) THERMAL SHUTDOWN UVLO VREF OVP VREG FB1 FB2 REFERENCE GENERATOR REF_1V6 REF_1V6 CVREF Figure 40. Functional Block Diagram PWM MODE The boost and inverting regulators in the ADP5071 operate at a fixed frequency set by an internal oscillator. At the start of each oscillator cycle, the MOSFET switch turns on, applying a positive voltage across the inductor. The inductor current increases until the current sense signal crosses the peak inductor current threshold that turns off the MOSFET switch; this threshold is set by the error amplifier output. During the MOSFET off time, the inductor current declines through the external diode until the next oscillator clock pulse starts a new cycle. It regulates the output voltage by adjusting the peak inductor current threshold. PSM MODE During light load operation, the regulators can skip pulses to maintain output voltage regulation. Skipping pulses increases the device efficiency. UNDERVOLTAGE LOCKOUT (UVLO) The undervoltage lockout circuitry monitors the PVINSYS pin voltage level. If the input voltage drops below the VUVLO_FALLING threshold, both regulators turn off. After the PVINSYS pin voltage rises above the VUVLO_RISING threshold, the soft start period initiates, and the regulators are enabled. OSCILLATOR AND SYNCHRONIZATION The ADP5071 initiates the drive of the boost regulator SW1 pin and the inverting regulator SW2 pin 180° out of phase to reduce peak current consumption and noise. A phase-locked loop (PLL)-based oscillator generates the internal clock and offers a choice of two internally generated frequency options or external clock synchronization. The switching frequency is configured using the SYNC/FREQ pin options shown in Table 6. For external synchronization, connect the SYNC/FREQ pin to a suitable clock source. The PLL locks to an input clock within the range specified by fSYNC. Table 6. SYNC/FREQ Pin Options SYNC/FREQ Pin Switching Frequency High 2.4 MHz Low 1.2 MHz External Clock 1 × clock frequency INTERNAL REGULATORS The internal VREG regulator in the ADP5071 provides a stable power supply for the internal circuitry. The VREG supply can be used to provide a logic high signal for device configuration pins but must not be used to supply external circuitry. The VREF regulator provides a reference voltage for the inverting regulator feedback network to ensure a positive feedback voltage on the FB2 pin. A current-limit circuit is included for both regulators to protect the circuit from accidental loading. |
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