Powering CoolRunner™ -II

CPLDs

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Agenda

• Regulator Overview– Linear vs. Switching– Linear Regulators– Switching Regulators

• CoolRunner-II Power-Up Recommendations

• Regulator Application Examples

• Our Favorite Regulators

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Linear vs. Switching

• Two main categories of regulators:– Linear:

• Most basic• Easy to use• Inexpensive

– Switching:• High efficiency• Can create output voltages that are higher than input voltages• Can produce multiple output voltages from a single input

source

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Linear Regulators

Linear Regulators use a voltage-controlled current source to force voltage to appear at the output terminal

The design specification of the current source defines the maximum load current that the regulator can supply

Dropout voltage is defined as the minimum voltage drop required across the regulator in order to maintain proper output regulation

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Linear Regulator Types

• Dropout Voltages of approximately 1.5V to 2.2V• Best suited for AC-Powered applications, where dropout

voltage is not a big concern

• Dropout Voltages of approximately 100 mV to 500 mV• Lower dropout = highest efficiency• LDO Regulators are ideal for battery powered applications• Have additional features and have better output voltage

precision

Low-Dropout (LDO) Regulators:

Standard Linear Regulators:

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Switching Regulators

Switching regulators use Pulse Width Modulation (PWM) to control output voltage

Total power consumed is proportional to duty cycle of PWM output. Therefore switching regulators are more power efficient than Linear Regulators

These regulators require external inductors and capacitors to form an L-C network. This network filters the PWM output and provides DC output voltage

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Switching Regulator Types

• Used to down convert a higher DC voltage to a lower DC voltage

• Switching Buck Regulators are almost always more efficient than LDO Regulators

• Useful in battery-powered applications where a single battery or series of batteries is not quite enough to reach full rail

• Boost regulation can only be accomplished by switching regulators

Boost Converters:

Buck Converters:

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CoolRunner-II Power-Up Recommendations

1) Vcc Ramp should be monotonic2) Vcc Rise time should be as fast as possible (< 4 ms)3) Vccint/Vccio power-up sequence

– Ramp Vccint before Vccio

4) Choose a regulator with sufficient current5) Use proper decoupling capacitor techniques

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Regulator Application Examples

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Micrel Semiconductor MIC221X Dual Output LDO Regulator• Key Features

• Multiple output voltages• Vout1 = 150 mA• Vout2 = 300 mA

• Low Dropout Voltage (80 mV @ 100 mA)• Low Noise• Available in 3mm x 3mm MLF Package

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Micrel Semiconductor MIC5211 Dual Output LDO Regulator• Key Features

• Similar to MIC221X family• More cost efficient solution• Higher dropout voltage and lower output current than MIC221X family

• 80 mA Output Current• 500 mV Dropout Voltage

• 2.5V - 16V input voltage specification

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Micrel Semiconductor MIC5247 LDO Regulator

• Key Features• 2.7V to 6V input voltage specification• 150 mA output current• 150 mV Dropout Voltage

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Texas Instruments TPS72118 Low-Dropout Linear Regulator

• Key Features• Capable of 150 mA load current• 150 - 200 mV Dropout Voltage @ 150 mA load• 1.8V to 5.5V input voltage specification• Requires only 0.1 uF capacitors

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National Semiconductor LP3964 Low-Dropout Linear Regulator

• Key Features• Capable of 800 mA load current• 240 mV Dropout Voltage @ 80 mA load• 2.5V - 7.0V input voltage specification

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ON Semiconductor NCP1400A Switching Boost Regulator

• Key Features• Capable of 100 mA load current• Start-up at 0.8V and can remain in regulation down to less than 0.2V• Available w/ 1.8V fixed output voltage

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LM317 Standard Linear Regulator

• Key Features• Capable of 1.0 - 1.5A load current• Adjustable output voltage• 2.5V Dropout voltage @ 1.5A• Many manufacturers: Linear Technology, National Semiconductor, Fairchild

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Our Favorite Regulators

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Our Favorite Regulators

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Our Favorite Regulators

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Summary

• For further reading get– XAPP389: Powering CoolRunner-II CPLDs

• Questions?