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ADP1612ARMZ-R7 Datenblatt(PDF) 11 Page - Analog Devices |
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ADP1612ARMZ-R7 Datenblatt(HTML) 11 Page - Analog Devices |
11 / 28 page ADP1612/ADP1613 Rev. A | Page 11 of 28 THEORY OF OPERATION FREQ SW PWM COMPARATOR UVLO COMPARATOR TSD COMPARATOR OSCILLATOR S R Q D COMPARATOR DREF + + 7 VIN CURRENT SENSING 5µA DRIVER BAND GAP N1 BG RESET 1.1M Ω AGND VIN UVLOREF TSENSE TREF ERROR AMPLIFIER VBG SOFT START 2 1 5µA VSS RCOMP CCOMP COMP SS FB CSS R1 R2 CIN VOUT 6 VIN L1 D1 A VOUT COUT 5 3 4 GND AGND >1.6V EN ADP1612/AD1613 8 VIN <0.3V >1.6V <0.3V Figure 34. Block Diagram with Step-Up Regulator Application Circuit The ADP1612/ADP1613 current-mode step-up switching converters boost a 1.8 V to 5.5 V input voltage to an output voltage as high as 20 V. The internal switch allows a high output current, and the high 650 kHz/1.3 MHz switching frequency allows for the use of tiny external components. The switch current is monitored on a pulse-by-pulse basis to limit it to 1.4 A typical (ADP1612) or 2.0 A typical (ADP1613). CURRENT-MODE PWM OPERATION The ADP1612/ADP1613 utilize a current-mode PWM control scheme to regulate the output voltage over all load conditions. The output voltage is monitored at FB through a resistive voltage divider. The voltage at FB is compared to the internal 1.235 V reference by the internal transconductance error amplifier to create an error voltage at COMP. The switch current is internally measured and added to the stabilizing ramp. The resulting sum is compared to the error voltage at COMP to control the PWM modulator. This current-mode regulation system allows fast transient response, while maintaining a stable output voltage. By selecting the proper resistor-capacitor network from COMP to GND, the regulator response is optimized for a wide range of input voltages, output voltages, and load conditions. FREQUENCY SELECTION The frequency of the ADP1612/ADP1613 is pin-selectable to operate at either 650 kHz to optimize the regulator for high efficiency or at 1.3 MHz for use with small external components. If FREQ is left floating, the part defaults to 650 kHz. Connect FREQ to GND for 650 kHz operation or connect FREQ to VIN for 1.3 MHz operation. When connected to VIN for 1.3 MHz operation, an additional 5 μA, typical, of quiescent current is active. This current is turned off when the part is shutdown. SOFT START To prevent input inrush current to the converter when the part is enabled, connect a capacitor from SS to GND to set the soft start period. Once the ADP1612/ADP1613 are turned on, SS sources 5 μA, typical, to the soft start capacitor (CSS) until it reaches 1.2 V at startup. As the soft start capacitor charges, it limits the peak current allowed by the part. By slowly charging the soft start capacitor, the input current ramps slowly to prevent it from overshooting excessively at startup. When the ADP1612/ ADP1613 are in shutdown mode (EN ≤ 0.3 V), a thermal shut- down event occurs, or the input voltage is below the falling undervoltage lockout voltage, SS is internally shorted to GND to discharge the soft start capacitor. |
Ähnliche Teilenummer - ADP1612ARMZ-R7 |
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Ähnliche Beschreibung - ADP1612ARMZ-R7 |
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