Texas Instruments LM25085A Скачать руководство пользователя страница 9 | Manualshive

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Circuit Performance

Figure 10. Output Voltage Ripple

Figure 11. Line Regulation

Figure 12. Load Regulation

9

SNVA384B – February 2009 – Revised April 2013

AN-1933 LM25085A Evaluation Board

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Copyright © 2009–2013, Texas Instruments Incorporated

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Содержание LM25085A

Страница 1: ...ent limit set at 8 2A The board is populated with all components except C5 and C7 The board s specification are Input Voltage 4 5V to 24V Output Voltage 1V Maximum load current 5A Minimum load current 0A Current Limit Threshold 8 2A Measured Efficiency 77 5 VIN 4 5V IOUT 1Amp typical efficiency for converter providing a 1V output Nominal Switching Frequency 200 kHz Size 3 1 in x 1 5 in Figure 1 Ev...

Страница 2: ...w the inductor current to decrease at least as much if not more than the current increase which occurred during the on time The circuit may be shutdown at any time by grounding the Enable test point EN TP1 Removing the ground connection allows normal operation to resume Refer to the LM25085A 42V Constant On Time PFET Buck Switching Controller with 0 9V Reference SNVS601 data sheet for a detailed b...

Страница 3: ...g forced off time provides effective protection from output load faults over a wide range of operating conditions Figure 2 Current Limit Off time vs VIN and VFB A Sense resistor method This evaluation board is supplied configured for the sense resistor method of current limit detection Jumpers A B are in place at both jumper locations JP1 JP2 which connects the ADJ pin resistor R3 and the ISEN pin...

Страница 4: ...nd C10 allowing the ripple at VOUT to be kept to a minimum as described in option A below Alternatively the required ripple at the FB pin can be supplied from ripple generated at VOUT and passed through the feedback resistors as described in options B and C below using one or two less external components A Minimum Output Ripple This evaluation board is supplied configured for minimum ripple at VOU...

Страница 5: ... current flows through R6 and that ripple voltage is passed to the FB pin via C5 The ripple at VOUT can be set as low as 25 mVp p since it is not attenuated by R1 and R2 The minimum value for R6 is calculated from 10 where IOR min is the minimum inductor s ripple current which occurs at minimum input voltage and is 622 mAp p at 4 5V The minimum value for R6 calculates to 0 04 ohms Using a standard...

Страница 6: ...t VOUT ranges from 32 mVp p to 43 mVp p over the input voltage range See Figure 10 If the application can accept this ripple level this is the most economical solution The circuit is shown in Figure 5 Figure 5 Lowest Cost Configuration 7 Monitor The Inductor Current The inductor s current can be monitored or viewed on a scope with a current probe Remove the jumper from the WIRE LOOP pads and insta...

Страница 7: ...ic Capacitor TKD C2012X7R2A332K 0805 3300 pF 100V D1 Schottky Diode On Semi D2PAK 35V 25A MBRB2535CTL L1 Power Inductor Wurth XXL 7447709006 12 mm x 12 mm 6 8 µH Q1 P Channel MOSFET Vishay Si7465DP SO 8 Power 60V 5A R1 Resistor Vishay 0805 1 1k CRCW08051101F R2 Resistor Vishay 0805 10k CRCW08051002F R3 Resistor Vishay 0805 2 05k CRCW08052051F R4 Resistor Vishay 0805 21k CRCW08052102F R5 Resistor V...

Страница 8: ...verter producing a 1 0V output Figure 7 Efficiency vs Load Current Figure 8 Efficiency vs Input Voltage Figure 9 Switching Frequency vs Input Voltage 8 AN 1933 LM25085A Evaluation Board SNVA384B February 2009 Revised April 2013 Submit Documentation Feedback Copyright 2009 2013 Texas Instruments Incorporated ...

Страница 9: ...e 10 Output Voltage Ripple Figure 11 Line Regulation Figure 12 Load Regulation 9 SNVA384B February 2009 Revised April 2013 AN 1933 LM25085A Evaluation Board Submit Documentation Feedback Copyright 2009 2013 Texas Instruments Incorporated ...

Страница 10: ...de Trace 4 Inductor Current Trace 3 VOUT Trace 1 SW Node VIN 12V IOUT 0 Figure 14 Discontinuous Conduction Mode Trace 4 Inductor Current Trace 3 VOUT Trace 1 SW Node VIN 12V IOUT 0 Figure 15 Discontinuous Conduction Mode Expanded Scale 10 AN 1933 LM25085A Evaluation Board SNVA384B February 2009 Revised April 2013 Submit Documentation Feedback Copyright 2009 2013 Texas Instruments Incorporated ...

Страница 11: ...e 16 Board Silkscreen Figure 17 Board Top Layer Figure 18 Board Bottom Layer Viewed from Top 11 SNVA384B February 2009 Revised April 2013 AN 1933 LM25085A Evaluation Board Submit Documentation Feedback Copyright 2009 2013 Texas Instruments Incorporated ...

Страница 12: ...esponsible for compliance with all legal regulatory and safety related requirements concerning its products and any use of TI components in its applications notwithstanding any applications related information or support that may be provided by TI Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failur...

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