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ADP1607 Fiches technique(PDF) 11 Page - Analog Devices |
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ADP1607 Fiches technique(HTML) 11 Page - Analog Devices |
11 / 16 page Data Sheet ADP1607 Rev. C | Page 11 of 16 operates in PFM mode for light load currents and switches to PWM mode for medium and heavy load currents. Pulse Frequency Modulation (PFM) When the auto mode version of the ADP1607 is operating under light load conditions, the effective switching frequency and supply current are decreased and varied using PFM to regulate the output voltage. This results in improved efficiencies and lower quiescent currents. In PFM mode, the converter only switches when necessary to keep the output voltage between the PFM comparator high output voltage threshold and the lower sleep mode exit voltage threshold. Switching stops when the upper PFM limit is reached and resumes when the lower sleep mode exit threshold is reached. When VOUT exceeds the upper PFM threshold, switching stops and the part enters sleep mode. In sleep mode, the ADP1607 is mostly shut down, significantly reducing the quiescent current. The output voltage is then discharged by the load until the output voltage reaches the lower sleep mode exit threshold. After crossing the lower sleep mode exit threshold, switching resumes and the process repeats. Mode Transition The auto mode version of the ADP1607 switches automatically between PFM and PWM modes to maintain optimal efficiency. Switching to PFM allows the converter to save power by sup- plying the lighter load current with fewer switching cycles. The mode transition point depends on the operating conditions. See Figure 14 for typical transition levels for VOUT = 2.5 V. Hysteresis exists in the transition point to prevent instability and decreased efficiencies that may result if the converter oscillates between PFM and PWM for a fixed input voltage and load current. The output voltage in PWM can be above or below the PFM voltage of that part. INTERNAL CONTROL FEATURES Input to Output Isolation While in shutdown, the ADP1607 manages the voltage of the bulk of the PMOS to force it off and internally isolate the path from the input to output. This allows the output to drop to ground, reducing the current consumption of the application in shutdown. Soft Start The ADP1607 soft start sequence is designed for optimal control of the part. When EN goes high, or when the part recovers from a TSD, the start-up sequence begins. The output voltage increases through a sequence of stages to ensure that the internal circuitry is powered up in the correct order as the output voltage rises to its final value. Current Limit The ADP1607 is designed with a fixed 1 A typical current limit that does not vary with duty cycle. Synchronous Rectification In addition to the N-channel MOSFET switch, the ADP1607 has a P-channel MOSFET switch to build the synchronous rectifier. The synchronous rectifier improves efficiency, especially for heavy load currents, and reduces cost and board space by eliminating the need for an external Schottky diode. Compensation The PWM control loop of the ADP1607 is internally compen- sated to deliver maximum performance with no additional external components. The ADP1607 is designed to work with 2.2 μH chip inductors and 10 μF ceramic capacitors. Other values may reduce performance and/or stability. Thermal Shutdown (TSD) Protection The ADP1607 includes thermal shutdown (TSD) protection when the part is in PWM mode only. If the die temperature exceeds 150°C (typical), the TSD protection activates and turns off the power devices. They remain off until the die temperature falls below 135°C (typical), at which point the converter restarts. |
Numéro de pièce similaire - ADP1607 |
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Description similaire - ADP1607 |
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