lm5035asqx National Semiconductor Corporation, lm5035asqx Datasheet
lm5035asqx
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lm5035asqx Summary of contents
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... The oscillator can also be synchronized to an external clock. A current sense input and a pro- grammable timer provide cycle-by-cycle current limit and ad- justable hiccup mode overload protection. Simplified Application Diagram © 2008 National Semiconductor Corporation Features ■ 105V / 2A Half-Bridge Gate Drivers ■ ...
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Connection Diagrams www.national.com Top View 20-Lead TSSOP EP Top View 30034103 LLP-24 Package 2 30034102 ...
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... Ordering Information Order Number Package Type LM5035AMH TSSOP-20EP LM5035AMHX TSSOP-20EP LM5035ASQ LLP-24 LM5035ASQX LLP-24 Pin Descriptions TSSOP LLP PIN Name PIN 1 23 RAMP Modulator ramp signal 2 24 UVLO Line Under-Voltage Lockout 3 2 OVP Line Over-Voltage Protection 4 3 COMP Input to the Pulse Width Modulator An external opto-coupler connected to the COMP pin sources ...
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TSSOP LLP PIN Name PIN Boost voltage for the HO driver Switch node High side gate drive output Low side gate drive output PGND Power Ground ...
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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 HS to GND HB to GND VCC to GND CS, RT, DLY to ...
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Symbol Parameter Soft-Start (SS Pin) I Charging current in normal SS operation Charging current during a hiccup mode restart Soft-stop Current Sink Oscillator (RT Pin) F Frequency 1 (at HO, half oscillator SW1 frequency) F Frequency 2 (at HO, half ...
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Symbol Parameter Thermal Shutdown T Shutdown temperature SD Hysteresis Thermal Resistance θ Junction to ambient, 0 LFPM Air JA Flow θ Junction to Case (EP) Thermal JC resistance θ Junction to ambient, 0 LFM Air Flow LLP- ...
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Typical Performance Characteristics V and V VCC REF REF REF Oscillator Frequency vs Temperature www.national.com vs V VIN 30034105 30034107 Soft-Start & Stop Current vs Temperature 30034109 VCC VCC 30034106 Frequency vs RT ...
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Effective Comp Input Impedance 30034111 SR "T1" Parameter vs Temperature 30034113 R vs Deadtime DLY SR "T2" Parameter vs Temperature 9 30034112 30034114 www.national.com ...
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Block Diagram www.national.com FIGURE 1. 10 30034104 ...
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Functional Description The LM5035A PWM controller contains all of the features necessary to implement half-bridge voltage-mode controlled power converters. The LM5035A provides two gate driver outputs to directly drive the primary side power MOSFETs and two signal level outputs to ...
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Cycle-by-Cycle Current Limit The CS pin is driven by a signal representative of the trans- former primary current. If the voltage sensed at CS pin ex- ceeds 0.25V, the current sense comparator terminates the output driver pulse. ...
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FIGURE 2. Current Limit Restart Circuit FIGURE 3. Current Limit Restart Timing 13 30034115 30034116 www.national.com ...
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Soft-Start The soft-start circuit allows the regulator to gradually reach a steady state operating point, thereby reducing start-up stress- es and current surges. When bias is supplied to the LM5035A, the SS pin capacitor is discharged by an internal MOSFET. ...
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VIN while the threshold of the clamp fixed voltage (2.5V). An example will illustrate the use of the Volt • Second Clamp comparator to achieve a 50% duty cycle limit at 200kHz ...
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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. The reduction of rectifier forward voltage drop (0.5V - 1.5V) to 10mV - 200mV V DS significantly ...
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Applications Information The following information is intended to provide guidelines for the power supply designer using the LM5035A. VIN The voltage applied to the VIN pin, which may be the same as the system voltage applied to the power transformer’s ...
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FIGURE 9. Current Sense Using Current Sense Resistor (R1) If the current sense resistor method is used, the over-current condition will only be sensed while LO is driving the low-side MOSFET. Over-current while HO is driving the high-side MOSFET will ...
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T2 = .0007 10.01 ns DLY T1 and T2 can be set to minimum by not connecting a resistor to DLY, connecting a resistor greater than 300kΩ from DLY to ground, or connecting DLY to the REF ...
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The impedance seen looking into the resistor divider from the UVLO and OVP pins determines the hysteresis level. UVLO and OVP enable and disable thresholds are calculated using Outputs disabled due to VIN falling below UVLO threshold Outputs enabled due ...
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FIGURE 13. Remote Standby and Disable Control To maintain the threshold’s accuracy, a resistor tolerance better is recommended. The design process starts with the choice of the voltage dif- ference between the UVLO enabling and disabling thresh- ...
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Figure 15 shows an application of the OVP comparator for Remote Thermal Protection using a thermistor (or multiple thermistors) which may be located near the main heat sources of the power supply. The negative temperature co- efficient (NTC) thermistor is ...
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If the application requires no delay from the first detection of a current limit condition to ...
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Printed Circuit Board Layout The LM5035A Current Sense and PWM comparators are very fast, and respond to short duration noise pulses. The compo- nents at the CS, COMP, SS, OVP, UVLO, DLY and the RT pins should be as physically ...
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Physical Dimensions www.national.com inches (millimeters) unless otherwise noted Molded TSSOP-20 NS Package Number MXA20A 24-Lead LLP Package NS Package Number SQA24B 26 ...
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Notes 27 www.national.com ...
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