Fast Synchronous- Buck MOSFET Drivers with Dead Time Control <ul><li>Source: Texas Instruments </li></ul>
Introduction <ul><li>Purpose </li></ul><ul><ul><li>An Overview study on Fast Synchronous Buck MOSFET Driver. </li></ul></u...
Features <ul><li>Floating Bootstrap or Ground-Reference High-Side Driver  </li></ul><ul><li>Adaptive Dead-Time Control  </...
Functional Block Diagram
Typical Characteristics of  Q1 - Control MOSFET Q1 RDS(on) vs VGS Q1 VGS vs QG
Typical Characteristics of  Q2 – Synchronous Rectifier MOSFET Q2 VGS vs QG Q2 RDS(on) vs VGS
High-Side/Low Side Driver <ul><li>Low-side Driver </li></ul><ul><li>The low-side driver is designed to drive low  </li></u...
Control Functions <ul><li>Dead-time (DT) Control: </li></ul><ul><li>Dead-time control prevents shoot through current from ...
CROWBAR <ul><li>The CROWBAR terminal overrides the normal operation of the driver. </li></ul><ul><li>When the CROWBAR term...
Application Information 3.3-V 3-A Synchronous-Buck Converter Circuit
Synchronous Buck Power  and Driver Stage
MOSFET Driver Parasitics
Additional Resource <ul><li>For ordering  TPS2831 , please click the part list or </li></ul><ul><li>Call our sales hotline...
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Fast Synchronous- Buck MOSFET Drivers with Dead Time Control

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An Overview study on Fast Synchronous Buck MOSFET Driver

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  • Welcome to the training module on TPS2831. This training module introduces the features of Fast Synchronous- Buck MOSFET Drivers with Dead Time Control.
  • The TPS2830 and TPS2831 are MOSFET drivers for synchronous-buck power stages. These devices are ideal for designing a high-performance power supply using switching controllers that do not have MOSFET drivers. The drivers are designed to deliver 2.4-A peak currents into large capacitive loads. The high-side driver can be configured as a ground-reference driver or as a floating bootstrap driver. An adaptive dead-time control circuit eliminates shoot-through currents through the main power Field effect transistors during switching transitions, providing higher efficiency for the buck regulator. The TPS2830/31 drivers have additional control functions: ENABLE, SYNC, and CROWBAR. Both drivers are off when ENABLE is low. The driver is configured as a non synchronous-buck driver, disabling the low side driver when SYNC is low.
  • The TPS2830/31 drivers have additional control functions: ENABLE, SYNC, and CROWBAR. Both drivers are off when ENABLE is low. The driver is configured as a non synchronous-buck driver, disabling the low side driver when SYNC is low. The CROWBAR function turns on the low-side power FET, overriding the IN signal, for over-voltage protection against faulted high-side power FETs. The TPS2830 has a non-inverting input. The TPS2831 has an inverting input.
  • This page shows Typical Characteristics of Q1 - Control MOSFET, Graphs here highlights the RDS(on) values for VGS = 5 V and VGS = 9 V for the control MOSFET, Q1. Since it is more prone to switching loss, Q1 is normally selected based primarily upon lower gate charge, with secondary consideration given to RDS(on).
  • This page shows Typical Characteristics of Q2 – Synchronous Rectifier MOSFET. the RDS(on) values for VGS = 5 V and VGS = 9 V for the synchronous rectifier MOSFET, Q2. Since it is more prone to conduction loss, Q2 is selected based upon lowest possible RDS(on), with secondary consideration given to gate charge.
  • High-side gate drivers are used to drive a MOSFET or IGBT that is connected to the positive supply and is not ground-referenced but is floating. High-side drivers are more complicated than low-side drivers because of the required voltage translation to the supply and because it is more difficult to turn off a floating transistor. It refers to how you drive a load. High side means your switch is between the plus power and the load; low side means the switch is between the load and negative power.
  • This Page gives information about control function of TPS2831 device. Dead time control prevents shoot through current from flowing through the main power FET during switching transitions by controlling the turn-on times of the MOSFET driver. The SYNC terminal controls whether the drivers operate in synchronous or non- synchronous mode.
  • The CROWBAR function turns on the low-side power FET, overriding the IN signal, for over-voltage protection against faulted high-side power FETs. CROWBAR can to be driven by an external OVP circuit to protect against a short across the high-side MOSFET. If CROWBAR is driven low, the low-side driver will be turned on and the high-side driver will be turned off, independent of the status of all other control terminals.
  • This Slide the circuit schematic of a 100-kHz synchronous-buck converter implemented with a TL5001A pulse-width-modulation (PWM) controller and a TPS2831 driver. The converter operates over an input range from 4.5 V to 12 V and has a 3.3-V output. The circuit can supply 3 A continuous load.
  • Driving the gates of control MOSFET Q1 and synchronous MOSFET Q2 with one voltage level verses another requires careful consideration In order to weigh the benefit of one gate-source voltage (VGS) versus another, the RDS(on) versus gate drive voltage and gate drive voltage versus gate charge curves for each MOSFET must be carefully looked at.
  • Figure shows a representative model illustrating most of the parasitic elements that can impact switching power supply performance. The resistances associated with the driver sink and source impedances quite often are not the same value It is also important to mention the effect of parasitic inductance between the driver and the MOSFET. At higher frequency operation, this inductance can limit the gate current trying to charge the MOSFET input capacitance therefore minimizing the length of trace between the driver and the MOSFET, as well as running a short and wide gate trace directly over a ground plane, will reduce parasitic trace inductance.
  • Thank you for taking the time to view this presentation on “ TPS2831 ” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the Texas Instruments site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility. You may visit Element 14 e-community to post your questions.
  • Fast Synchronous- Buck MOSFET Drivers with Dead Time Control

    1. 1. Fast Synchronous- Buck MOSFET Drivers with Dead Time Control <ul><li>Source: Texas Instruments </li></ul>
    2. 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>An Overview study on Fast Synchronous Buck MOSFET Driver. </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Features and Functional Block Diagram. </li></ul></ul><ul><ul><li>Typical Characteristics of the Device. </li></ul></ul><ul><ul><li>High-Low Side Driver Concept. </li></ul></ul><ul><ul><li>Control Functions, Crowbar. </li></ul></ul><ul><ul><li>Application Circuit. </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>13 pages </li></ul></ul>
    3. 3. Features <ul><li>Floating Bootstrap or Ground-Reference High-Side Driver </li></ul><ul><li>Adaptive Dead-Time Control </li></ul><ul><li>50-ns Max Rise/Fall Times and 100-ns Max Propagation Delay </li></ul><ul><li>x96 3.3-nF Load </li></ul><ul><li>Ideal for High-Current Single or Multiphase Power Supplies </li></ul><ul><li>2.4-A Typical Peak Output Current </li></ul><ul><li>4.5-V to 15-V Supply Voltage Range </li></ul><ul><li>Internal Schottky Bootstrap Diode </li></ul><ul><li>SYNC Control for Synchronous or Non synchronous Operation </li></ul><ul><li>CROWBAR for OVP, Protects Against Faulted High-Side </li></ul><ul><li>Power FETs </li></ul><ul><li>Low Supply Current....3-mA Typical x96 </li></ul><ul><li>40°C to 125°C Operating Temperature Range </li></ul><ul><li>Available in SOIC and TSSOP PowerPAD Packages. </li></ul>
    4. 4. Functional Block Diagram
    5. 5. Typical Characteristics of Q1 - Control MOSFET Q1 RDS(on) vs VGS Q1 VGS vs QG
    6. 6. Typical Characteristics of Q2 – Synchronous Rectifier MOSFET Q2 VGS vs QG Q2 RDS(on) vs VGS
    7. 7. High-Side/Low Side Driver <ul><li>Low-side Driver </li></ul><ul><li>The low-side driver is designed to drive low </li></ul><ul><li>Rds(on) N-channel MOSFETs. </li></ul><ul><li>The current rating of the driver is 2 A, source </li></ul><ul><li>and sink. </li></ul><ul><li>High-side Driver </li></ul><ul><li>The high-side driver is designed to drive low </li></ul><ul><li>Rds(on) N-channel MOSFETs. </li></ul><ul><li>The current rating of the driver is 2 A, source </li></ul><ul><li>and sink. </li></ul><ul><li>The high-side driver can be configured as a </li></ul><ul><li>GND-reference driver or as a floating </li></ul><ul><li>bootstrap driver. </li></ul><ul><li>The internal bootstrap diode is a Schottky, </li></ul><ul><li>for improved drive efficiency. </li></ul><ul><li>The maximum voltage that can be applied </li></ul><ul><li>from BOOT to ground is 30 V. </li></ul>Low Side Driver Block Diagram High Side Driver Block Diagram
    8. 8. Control Functions <ul><li>Dead-time (DT) Control: </li></ul><ul><li>Dead-time control prevents shoot through current from flowing through </li></ul><ul><li>the main power FETs during switching transitions by controlling the </li></ul><ul><li>turn-on times of the MOSFET drivers. </li></ul><ul><li>The high-side driver is not allowed to turn on until the gate drive voltage </li></ul><ul><li>to the low-side FET is low, and the low-side driver is not allowed to turn </li></ul><ul><li>on until the voltage at the junction of the power FETs (Vdrain) is low. </li></ul><ul><li>DT terminal connects to the junction of the power FETs. </li></ul><ul><li>SYNC </li></ul><ul><li>The SYNC terminal controls whether the drivers operate in </li></ul><ul><li>synchronous or non- synchronous mode. </li></ul><ul><li>In synchronous mode, the low-side FET is operated as a synchronous </li></ul><ul><li>rectifier. </li></ul><ul><li>In non-synchronous mode, the low-side FET is always off. </li></ul>
    9. 9. CROWBAR <ul><li>The CROWBAR terminal overrides the normal operation of the driver. </li></ul><ul><li>When the CROWBAR terminal is low. The low-side FET turns on to act </li></ul><ul><li>as a clamp, protecting the output voltage of the dc/dc converter against </li></ul><ul><li>over voltages due to a short across the high-side FET. VIN should be </li></ul><ul><li>fused to protect the low-side FET. </li></ul>
    10. 10. Application Information 3.3-V 3-A Synchronous-Buck Converter Circuit
    11. 11. Synchronous Buck Power and Driver Stage
    12. 12. MOSFET Driver Parasitics
    13. 13. Additional Resource <ul><li>For ordering TPS2831 , please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li>http://focus.ti.com/docs/prod/folders/print/tps2831.html </li></ul></ul><ul><li>Visit Element 14 to post your question </li></ul><ul><ul><li> www.element-14.com </li></ul></ul><ul><li>For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility </li></ul>Newark Farnell

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