SM72485

Manufacturer Part NumberSM72485
ManufacturerTexas Instruments
SM72485 datasheet
 


Specifications of SM72485

Pin/package8QFN, 8VSSOP, 8WSON  
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SM72485
SM72485 SolarMagic 100V, 150 mA Constant On-Time Buck Switching Regulator
Literature Number: SNVS697C

SM72485 Summary of contents

  • Page 1

    ... SM72485 SM72485 SolarMagic 100V, 150 mA Constant On-Time Buck Switching Regulator Literature Number: SNVS697C ...

  • Page 2

    ... SolarMagic 100V, 150 mA Constant On-Time Buck Switching Regulator General Description The SM72485 Step Down Switching Regulator features all of the functions needed to implement a low cost, efficient, Buck bias regulator. This high voltage regulator contains an 100 V N-Channel Buck Switch. The device is easy to implement and is provided in the MSOP-8 and the thermally enhanced LLP-8 package ...

  • Page 3

    ... 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 ...

  • Page 4

    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 ...

  • Page 5

    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 ...

  • Page 6

    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 ...

  • Page 7

    ... Gate drive under-voltage lockout, Max Duty Cycle limit timer, intelligent current limit off timer, and a pre-charge switch. Control Circuit Overview The SM72485 is a Buck DC-DC regulator that uses a control scheme in which the on-time varies inversely with line voltage (V ). Control is based on a comparator and the on-time one- ...

  • Page 8

    ... When V is above the bypass thresh- IN old Q2 is turned off, and V is regulated at 7V. The V CC regulator output current is limited at approximately 9.2 mA. When the SM72485 is shutdown using the RT/SD pin, the V bypass switch is shut off regardless of the voltage When VIN exceeds the bypass threshold, the time required for Q2 to shut off is approximately µ ...

  • Page 9

    ... FIGURE 2. Startup Sequence On-Time Generator and Shutdown The on-time for the SM72485 is determined by the R and is inversely proportional to the input voltage (Vin), result- ing in a nearly constant frequency as Vin is varied over its range. The on-time equation for the SM72485 is ...

  • Page 10

    ... F and R : The recommended operating frequency range for s T the SM72485 is 50 kHz to 1.1 MHz. Unless the application requires a specific frequency, the choice of frequency is gen- erally a compromise since it affects the size of L1 and C2, and the switching losses. The maximum allowed frequency ...

  • Page 11

    ... However, the regulator requires a minimum amount of ripple voltage at the feedback input for proper loop operation. For the SM72485 the minimum ripple required at pin p-p, requiring a minimum ripple at V minimum ripple current (at minimum Vin p-p, the minimum ESR required 100 mV/ 3.12Ω ...

  • Page 12

    ... FB2 R Resistor FB1 R3 Resistor R Resistor T R Resistor CL U1 Switching Regulator FIGURE 4. SM72485 Example Circuit Part Number TDK C4532X7R2A105M TDK C4532X7R1E226M Kemet C1206C474K5RAC Kemet C1206C103K5RAC TDK C3216X7R2A104M Diodes Inc. DFLS1100 COILTRONICS DR125-221-R, or TDK SLF10145T-221MR65 Vishay CRCW12063011F Vishay CRCW12061001F Vishay CRCW12063R30F Vishay CRCW12063093F ...

  • Page 13

    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 ...

  • Page 14

    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. ...

  • Page 15

    FIGURE 9. Alternate Minimum Output Ripple 14 30142323 ...

  • Page 16

    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 ...

  • Page 17

    For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Amplifiers www.national.com/amplifiers Audio www.national.com/audio Clock and Timing www.national.com/timing Data Converters www.national.com/adc Interface www.national.com/interface LVDS www.national.com/lvds Power Management www.national.com/power Switching Regulators www.national.com/switchers LDOs ...

  • Page 18

    ... Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’ ...