lm5045sqx National Semiconductor Corporation, lm5045sqx Datasheet
lm5045sqx
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lm5045sqx Summary of contents
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... MHz capable oscillator with synchronization capability and thermal shutdown. Packages ■ eTSSOP-28 ■ LLP-28 (5mm x 5mm) Simplified Full-Bridge Power Converter © 2011 National Semiconductor Corporation LM5045 Features ■ Highest Integration Controller for Small Form Factor, High Density Power Converters ■ High Voltage Start-up Regulator ■ ...
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Connection Diagrams www.national.com Top View 30145402 TSSOP28 2 ...
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... Ordering Information Order Number Package Type LM5045MH eTSSOP-28 LM5045MHX eTSSOP-28 LM5045SQ LLP-28 LM5045SQX LLP-28 Pin Descriptions TSSOP LLP Pin Name Pin 1 25 UVLO Line Under-Voltage Lockout 2 26 OVP/OTP Over Voltage Protection Top View LLP-28 Package NSC Package Drawing MXA28A MXA28A SQA28A ...
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TSSOP LLP Pin Name Pin 3 27 RAMP Input to PWM Comparator Current Sense Input 5 1 SLOPE Slope Compensation Current 6 2 COMP Input to the Pulse Width Modulator An external opto-coupler connected to the COMP ...
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TSSOP LLP Pin Name Pin 19 15 SR2 Synchronous Rectifier Driver 21 17 VCC Output of Start-Up Regulator 22 18 PGND Power Ground 23, 20 19, 16 LO1, LO2 Low Side Output Driver 24 20 SR1 Synchronous Rectifier Driver 25, ...
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Absolute Maximum Ratings VIN to GND HS to GND(Note 4) BST1/BST2 to GND BST1/BST2 to HS1/HS2 HO1/HO2 to HS1/HS2(Note 2) LO1/LO2/SR1/SR2(Note GND CC REF,SSOFF,RT,OVP,UVLO to GND RAMP COMP Electrical Characteristics junction temperature range of -40°C to +125°C. ...
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Symbol Parameter I SSSR charge current SSSR I SSSR discharge current 1 SSSR-DIS1 I SSSR discharge current 2 SSSR-DIS2 SSSR output low voltage SSSR threshold to enable SR1/SR2 Current Sense Input (CS Pin) V Current limit threshold CS CS delay ...
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Symbol Parameter Comp Pin V COMP current to RAMP offset PWM- RAMP offset SS-OS COMP current to RAMP gain SS to RAMP gain COMP current for SSSR charge current enable COMP to output delay Minimum duty cycle ...
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Typical Performance Characteristics Application Board Efficiency 100 OUT = 3. LOAD CURRENT (A) V and V vs. V VCC REF V vs. I REF REF 36V 48V 72V 25 30 ...
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Dead-Time T1 Threshold vs. Temperature www.national.com , R Dead-Time T1, T2 vs. Temperature 30145457 30145413 - 100 150 TEMPERATURE(°C) 30145454 ...
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Block Diagram FIGURE 1. 11 30145404 www.national.com ...
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Functional Description The LM5045 PWM controller contains all of the features nec- essary to implement a Full-Bridge topology power converter using either current mode or voltage mode control. This de- vice is intended to operate on the primary side of ...
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The synchronization pulse width should be between 15 and 200ns. The RT resistor is always required, whether the oscil- lator ...
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PWM Comparator The LM5045 pulse width modulator (PWM) comparator is a three input device, it compares the signal at the RAMP pin to the loop error signal or the soft-start, whichever is lower, to control the duty cycle. This comparator ...
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Soft-Start The soft-start circuit allows the power converter to gradually reach a steady state operating point, thereby reducing the start-up stresses and current surges. When bias is supplied to the LM5045, the SS capacitor is discharged by an internal MOSFET. ...
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Synchronous Rectifier Control Outputs (SR1 & SR2) Synchronous rectification (SR) of the transformer secondary provides higher efficiency, especially for low output voltage converters, compared to the diode rectification. The reduction of rectifier forward voltage drop (0.5V - 1.5V) to 10mV ...
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Soft-Start of the Synchronous Rectifiers In addition to the basic soft-start already described, the LM5045 contains a second soft-start function that gradually turns on the synchronous rectifiers to their steady-state duty cycle. This function keeps the synchronous rectifiers off dur- ...
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Soft-Stop Off The Soft-Start Off (SSOFF) pin gives additional flexibility by allowing the power converter to be configured for hard-stop during line UVLO and hiccup mode condition. If the SS OFF FIGURE 8. Stop-Stop Waveforms during a UVLO Event www.national.com ...
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Table 1: Soft-Stop in Fault Conditions Fault Condition UVLO (UVLO<1.25V) 3x the charging rate OVP (OVP>1.25V) Hiccup (CS>0.75 and RES>1V) 6x the charging rate VCC/VREF UV Internal Thermal Limit Note: All the above conditions are valid with SSOFF pin tied ...
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The recommended capacitor value range for C 100pF to 1800pF. Referring to Figure 9, it can be seen that C value must be small enough to be discharged with in the FF clock pulse-width which is typically within 50ns. The ...
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FIGURE 12. Start-up Regulator for VPWR>100V UVLO AND OVP VOLTAGE DIVIDER SELECTION Two dedicated comparators connected to the UVLO and OVP pins are used to detect under voltage and over voltage con- ditions. The threshold values of both these comparators ...
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FIGURE 13. Basic UVLO Configuration FIGURE 14. Basic OVP Configuration FIGURE 15. UVLO/OVP Divider 22 30145438 30145439 30145443 ...
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The UVLO and OVP can also be set together using a 3 re- sistor divider ladder as shown in Figure 15 explained in the basic UVLO divider selection. Using the same values the above two examples, ...
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CURRENT SENSE The CS pin receives an input signal representative of its transformer’s primary current, either from a current sense transformer or from a resistor located at the junction of source pin of the primary switches, as shown in Figure ...
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HICCUP MODE CURRENT LIMIT RESTART The operation of the hiccup mode restart circuit is explained in the Functional Description section. During a continuous current limit condition, the RES pin is charged with 30µA cur- rent source. The restart delay time ...
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Evaluation Board Schematic www.national.com 26 ...
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Physical Dimensions inches (millimeters) unless otherwise noted Molded TSSOP-28 NS Package Number MXA28A 28-Lead LLP Package NS Package Number SQA28A 27 www.national.com ...
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