sm72485sdx National Semiconductor Corporation, sm72485sdx Datasheet
sm72485sdx
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sm72485sdx Summary of contents
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... No loop compensation required ■ Ultra-Fast transient response ■ On time varies inversely with input voltage Typical Application, Basic Step-Down Regulator © 2011 National Semiconductor Corporation SM72485 ■ Operating frequency remains constant with varying line voltage and load current ■ Adjustable output voltage from 2.5V ■ ...
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... Connection Diagrams Top View 8-Lead LLP Ordering Information Order Number Package Type SM72485SDE SM72485SD LLP-8 SM72485SDX SM72485MME SM72485MM MSOP-8 SM72485MMX Pin Descriptions Pin Name Description 1 SW Switching Node 2 BST Boost Pin (Boot–strap capacitor input) 3 RCL Current Limit OFF time set pin ...
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Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications GND IN BST to GND SW to GND (Steady State) ESD Rating (Note 5) Human Body Model ...
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Symbol Parameter Minimum Off Time Minimum Off Timer Regulation and OV Comparators FB Reference Threshold FB Over-Voltage Threshold FB Bias Current Thermal Shutdown Tsd Thermal Shutdown Temp. Thermal Shutdown Hysteresis Thermal Resistance θ Junction to Ambient JA Note 1: Absolute ...
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Typical Performance Characteristics Efficiency vs. Load Current and V (Circuit of Figure ON-Time vs Input Voltage and R Maximum Frequency vs 30142324 Current Limit Off-Time vs 30142325 and V I OUT IN CC 30142326 5 ...
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Block Diagram Functional Description The SM72485 Step Down Switching Regulator features all the functions needed to implement a low cost, efficient, Buck bias power converter. This high voltage regulator contains a 100 V N-Channel Buck Switch, is easy to implement ...
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The SM72485 regulates the output voltage based on ripple voltage at the feedback input, requiring a minimum amount of ESR for the output capacitor C2. A minimum of 25mV to 50mV of ripple voltage at the feedback pin (FB) is ...
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Regulation Comparator The feedback voltage compared to an internal 2.5V reference. In normal operation (the output voltage is regulat- ed), an on-time period is initiated when the voltage at FB falls below 2.5V. The buck switch will ...
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FIGURE 3. Shutdown Implementation Current Limit The SM72485 contains an intelligent current limit OFF timer. If the current in the Buck switch exceeds 0.3A the present cycle is immediately terminated, and a non-resetable OFF timer is initiated. The length of ...
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SM72485’s current limit threshold (360 mA) with- out saturating, since the current limit is reached during start- up. The ...
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Bill of Materials Item Description C1 Ceramic Capacitor C2 Ceramic Capacitor C3 Ceramic Capacitor C4 Ceramic Capacitor C5 Ceramic Capacitor D1 Schottky Power Diode L1 Power Inductor R Resistor FB2 R Resistor FB1 R3 Resistor R Resistor T R Resistor ...
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LOW OUTPUT RIPPLE CONFIGURATIONS For applications where low output ripple is required, the fol- lowing options can be used to reduce or nearly eliminate the ripple. a) Reduced ripple configuration: In across R to AC-couple the ripple at V FB2 ...
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Minimum ripple configuration: If the application requires a lower value of ripple (<10 mVp-p), the circuit of be used removed, and the resulting output ripple volt- age is determined by the inductor’s ripple current and C2’s characteristics. ...
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FIGURE 9. Alternate Minimum Output Ripple 14 30142323 ...
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Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead LLP Package NS Package Number SDC08B 8-Lead MSOP Package NS Package Number MUA08A 15 www.national.com ...
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... National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other brand or product names may be trademarks or registered trademarks of their respective holders. ...