lm5027mhx National Semiconductor Corporation, lm5027mhx Datasheet
lm5027mhx
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lm5027mhx Summary of contents
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... Additional features include Line Under Voltage Lockout (UVLO), separate soft- start of main and synchronous rectifier outputs, a timer for hiccup mode current limiting, a precision reference, and ther- mal shutdown. Typical Application Circuit © 2009 National Semiconductor Corporation LM5027 Features ■ Voltage-Mode control ■ ...
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... Connection Diagrams 20-Lead eTSSOP Ordering Information Order Number Package Type LM5027MH eTSSOP-20 LM5027MHX eTSSOP-20 LM5027SQ LLP-24 LM5027SQX LLP-24 www.national.com 30099002 NSC Package Drawing Package Marking MXA20A LM5027MH MXA20A LM5027MH SQA24B L5027 SQA24B L5027 2 30099090 24-Lead LLP Supplied As 73 units per Rail ...
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Pin Descriptions Pin Name Description 1 VIN Input voltage source 2 RAMP Feed-forward modulation ramp 3 TIME3 Overlap delay 3 4 TIME2 Overlap delay 2 5 TIME1 Overlap delay 1 6 AGND Analog ground 7 RT Oscillator frequency control and ...
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Pin Name Description 17 RES Restart timer 18 SSSR Soft-start for synchronous rectifier output. 19 OTP Over-Temperature Protection 20 UVLO Line under-voltage lockout EP Exposed pad, underside of package Note: The pin numbers shown are only for the eTSSOP package. ...
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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. VIN to GND VCC to GND UVLO to GND All other inputs to GND COMP Input Current COMP, REF ...
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Symbol Parameter OSCILLATOR Frequency1 Frequency2 Sync Threshold Sync Pulse Width Sync Frequency Range PWM COMPARATORS Delay to Output COMP to PWM Offset Duty Cycle Maximum CURRENT LIMIT RESTART (RES Pin) RES Threshold Charge Source Current Level 1 V Charge Source ...
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Symbol Parameter OUTSR GATE DRIVER VOL OUTSR Low-state Output Voltage VOH OUTSR High-state Output Voltage OUTSR Rise Time OUTSR High Side Fall Time IOHH Peak OUTSR Source Current IOLH Peak OUTSR Source Current OUTPUT TIMING CONTROL T1 Delay Leading Range ...
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Typical Performance Characteristics Efficiency VCC vs. I Oscillator Frequency vs R www.national.com 30099040 CC 30099025 Resistor T 30099027 8 VCC and V vs. VIN REF 30099024 V vs. I REF REF 30099026 Oscillator Frequency vs Temperature 30099028 ...
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Time1 Delay vs R (kΩ) TIME1 30099029 Time3 Delay vs R (kΩ) TIME3 30099031 Time2 Delay vs Temperature R = 28.7 kΩ TIME2 30099033 Time2 Delay vs R TIME2 Time1 Delay vs Temperature R = 33.2 kΩ TIME1 Time3 Delay ...
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SS Pin Current vs Temperature RES Pin Charging Current Level 1 vs Temperature www.national.com SSSR Pin Charging Current vs Temperature 30099035 30099037 10 30099036 ...
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Block Diagram FIGURE 1. Simplified Block Diagram 11 30099003 www.national.com ...
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Detailed Operating Description The LM5027 PWM controller contains all the features neces- sary to implement power converters utilizing the Active Clamp Reset technique with synchronous rectification. The device is configured to control a P-Channel clamp switch. With the ac- tive ...
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RES pin to gradually increase. If the RES voltage reaches the 1.0V threshold, the following restart se- quence occurs (also see Figure 2). • The SS and SSSR capacitors are fully discharged. • The RES 20 ...
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Soft-Start The soft-start circuit allows the regulator to gradually increase its output voltage until the steady state operating point is reached; thereby reducing start-up stresses and surge cur- rents. When bias power is supplied to the LM5027, the SS pin ...
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FIGURE 4. Soft-Start/Soft-Stop Timing FIGURE 5. Soft-Start and Drive Enable 15 30099006 30099007 www.national.com ...
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External Over-Temperature Protection An external set-point voltage divider between the REF, OTP, and AGND pins, as shown in Figure plement over-temperature protection shutdown. Typically a NTC thermistor is installed as the lower device of the voltage divider. The divider must ...
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Fault/Event Vcc UVLO UVLO<0.4V >6.2V - 2.0V<UVLO >6.2V - >0.4V SS< 1V >6.2V >2.0V SSSR <2.0V >6.2V >2.0V OTP >6.2V >2.0V <1.25V PWM Comparators The pulse width modulator (PWM) comparator compares the voltage ramp signal at the RAMP pin to ...
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Volt-Second Clamp An external resistor (R ) and a capacitor (C FF between the VIN, RAMP and AGND pins is required to create a saw-tooth modulation ramp signal as shown in slope of the RAMP will vary in proportion to ...
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Gate Drive Outputs The LM5027 contains three unique gate drivers. OUTA, the primary switch driver, is designed to drive the gate Channel MOSFET and is capable of sourcing and sinking a peak current of 2A. The active ...
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For Applications > 100V For applications where the system input voltage (V ceeds 100V, VIN can be powered from an external start-up regulator as shown in Figure 11. Connecting the VIN and VCC pins together allows the LM5027 to be ...
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FIGURE 12. UVLO Circuit with Shutdown Control Oscillator The oscillator frequency is generally selected in conjunction with the system magnetic components and any other aspects of the system which may be affected by the frequency. The R resistor selection equation ...
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Current Sense The CS pin receives an input signal representative of the transformer primary current, either from a current sense transformer or from a resistor in series with the source of the primary switch, as shown in Figure 14 cases ...
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Soft-Start The capacitor on the SS pin determines the time required for the output duty cycle to increase from zero to its final value for regulation. The minimum acceptable time is dependent on the output capacitance and the response of ...
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The hiccup mode provides the periodic cool-down time for the power converter in the event of a sustained overload or short Printed Circuit Board Layout The LM5027 Current Sense and PWM comparators are very fast and respond to short duration ...
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25 www.national.com ...
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Physical Dimensions www.national.com inches (millimeters) unless otherwise noted 20 Lead eTSSOP NS Package Number MXA20A 24 Lead LLP NS Package Number SQA24B 26 ...
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Notes 27 www.national.com ...
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