A4401 Allegro MicroSystems, Inc., A4401 Datasheet
A4401
Related parts for A4401
A4401 Summary of contents
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... Internal diagnostics provide comprehensive protection against overloads, input undervoltage, and overtemperature conditions. The A4401 is supplied in an 8-pin narrow SOIC package (suffix L), which is lead (Pb) free, with 100% matte-tin leadframe plating. Typical Application VIN ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC Selection Guide Part Number A4401KL-T Tube, 98 pieces/tube A4401KLTR-T Tape and reel, 3000 pieces/reel *Contact Allegro for additional packing options. Absolute Maximum Ratings* Characteristic VIN Pin Voltage LX Pin Voltage ISS Pin Voltage EN Pin Voltage VA Pin Voltage ESD Rating – Human Body Model ESD Rating – ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC Optional V BAT EMI Filter 7 to 40V VIN Linear Adaptive turn-on control Control Enable Logic kΩ Shutdown UVLO Fault TSD GND VIN COMP GND ISS 4 5 Functional Block Diagram C3 100 nF ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC 1,2 ELECTRICAL CHARACTERISTICS Characteristics General VIN Quiescent Current LX Leakage Current LX Input Bias Current Minimum Frequency Soft Start Gate Drive Drive High Voltage, V > Drive High Voltage > V > Rise Time, V > Rise Time > V > ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC Basic Operation A peak current-mode control scheme is used to regu- late one of the converter outputs, which will typically be the highest output voltage. The regulated output voltage is potentially divided down and fed into a Gm stage, where the resulting error signal acts as the control reference ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC In the event of an overload, the current demand signal produced by the Gm amplifier restricts the output cur- rent by introducing pulse-by-pulse current limiting. Regulation Voltage The feedback resistors, R5 and R6, determine the voltage of the output rail to which they are connected, according to the following formula: × ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC If there is a special requirement for larger output capacitors, and the onboard soft start is insufficient, an external soft start can be introduced. This can be implemented by “pulling” down the amplifier output (COMP pin) and then “releasing” it gradually over the duration of the new soft start period. The pull-down circuit has to be capable of sinking at least 30 μ ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC The turn-on losses are Switching Turn-On Losses determined by the amount of energy the resonant capacitor, C11, has to discharge into the MOSFET. At low battery voltage, the resonant swing should force the volts across the capacitor to only a few volts, mak- ing this loss negligible ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC for more information). The current that flows in and out of the capacitor is similar to the current that flows through the corresponding rectifier diode. Worst case power dissipation due to the ESR will occur at V (min) and maximum load. The duty BAT cycle under these conditions is a maximum of 0 ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC • Magnetics sizing can be determined using techniques such as area product or geometric product fol- lowing manufacturers guidelines, usually in the form of nomograms. To simplify the design process, the resonant switch- ing transition is ignored and the calculations are based on the switcher operating at the boundary condition of continuous/discontinuous conduction ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC then: μ × (approx Because of flux fringing effects, the above air gap should be modified, according to the following formu- las. Given: (approx) ⎛ ⎜ ⎜ × ln ½ ⎝ where l (approx) is the previously calculated approxi- ...
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... RES L ⎝ ⎠ PRI is a half resonant period of 1 μ minimize parasitic noise appearing L PRI V BAT A4401 C IN Minimize this loop area Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com (34) LX node MOSFET Q1 ISS node ...
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... Figure 3 illustrates the main power loop. A local ground plane around the A4401 can be used to minimize ground bounce issues. This can be done with a simple connection from the ground pin of the A4401 to the star ground, being careful to avoid any connec- tion between this local ground plane and the power loop ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC It can be seen that at MOSFET turn-on there is a considerable sinusoidal ringing on the voltage sense, in the region of 3 MHz. In addition, there is a con- siderable ringing during the MOSFET turn-off, in the region of 6 MHz. These ringing effects are caused by the primary-to-secondary leakage inductance interact- ing with parasitic capacitance ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC A simple low-loss R-C snubber can be deployed to dampen these oscillations so, follow these sim- ple steps to determine the component values required: 1. Measure the voltage resonant frequency, f the LX node. 2. Add an additional capacitance (C11) between LX and ground until the resonant frequency is halved, ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC The capacitance selection has been dealt with in the Input Capacitor Selection section. In terms of select- ing an inductance, generally the higher the inductance the better as far as noise rejection of the differen- tial conducted emissions is concerned. However, a large inductance usually means additional cost and ...
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... A4401 Automotive Quasi-Resonant Flyback Control IC 4.90 ±0. 0.20 C 0.41 ±0.10 Copyright ©2007-2008, Allegro MicroSystems, Inc. The products described here are manufactured under one or more U.S. patents or U.S. patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec tions as may be required to per- mit improvements in the per for mance, reliability, or manufacturability of its products ...