Fairchild RC5042 Output Ripple and Noise, Efficiency, Processor Voltage Identification, Controls

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AN42

 

 

APPLICATION NOTE

 

 

 

 

Table 2. Intel Pentium Pro and OverDrive Processor Power Specifications

 

 

 

 

 

 

 

Voltage

Maximum

Maximum Thermal

 

Specification

Current

Design Power1

CPU Model & Features

VCCP (VDC)

ICCP (A)

(W)

 

 

 

 

150MHz – 256K L2 Cache

3.1 ± 5%

9.9

29.2

 

 

 

 

166MHz – 512K L2 Cache

3.3 ± 5%

11.2

35.0

 

 

 

 

180MHz – 256K L2 Cache

3.3 ± 5%

10.1

31.7

 

 

 

 

200MHz – 256K L2 Cache

3.3 ± 5%

11.2

35.0

 

 

 

 

200MHz – 512K L2 Cache

3.3 ± 5%

12.4

37.9

 

 

 

 

OverDrive Processors

 

 

 

150 MHz

2.5 ± 5%

11.2

26.7

180 MHz

 

12.5

29.7

200 MHz

 

13.9

32.9

 

 

 

 

Flexible Motherboard2

2.4-3.5 ± 5%

14.5

45.0

Notes:

1.Maximum power values are measured at typical VCCP to take into account the thermal time constant of the CPU package.

2.Flexible motherboard specifications are recommendations only. Actual specifications are subject to change.

Output Ripple and Noise

Ripple and noise are defined as periodic or random signals over the frequency band of 20MHz at the output pins. Output ripple and noise requirements of ±1.0% must be met throughout the full load range and under all specified input voltage conditions.

Efficiency

The efficiency of the DC-DC converter must be greater than 80% at high current draw and greater than 40% at low current draw.

Processor Voltage Identification

The Pentium Pro package has four voltage identification pins, VID3–VID0, that can be used for automatic selection of the power supply voltage. These pins are internally uncon- nected or are shorted to ground (VSS). The logic status of the pins defines the voltage required by the processor. The VID codes have been implemented to support voltage specifica- tion variations on future Pentium Pro processors. These codes are presented in Table 3. A ‘1’ refers to an open pin and a ‘0’ refers to a short to ground. The VCCP power supply should supply the voltage that is requested or disable itself.

Table 3. Voltage Identification Codes for Pentium Pro

 

Data Bits

 

VCCP

 

 

 

 

 

VID3

VID2

VID1

VID0

(VDC)

 

 

 

 

 

1

1

1

1

No CPU

 

 

 

 

 

1

1

1

0

2.1

 

 

 

 

 

1

1

0

1

2.2

 

 

 

 

 

1

1

0

0

2.3

 

 

 

 

 

1

0

1

1

2.4

 

 

 

 

 

1

0

1

0

2.5

 

 

 

 

 

1

0

0

1

2.6

 

 

 

 

 

1

0

0

0

2.7

 

 

 

 

 

0

1

1

1

2.8

 

 

 

 

 

0

1

1

0

2.9

 

 

 

 

 

0

1

0

1

3.0

 

 

 

 

 

0

1

0

0

3.1

 

 

 

 

 

0

0

1

1

3.2

 

 

 

 

 

0

0

1

0

3.3

 

 

 

 

 

0

0

0

1

3.4

 

 

 

 

 

0

0

0

0

3.5

 

 

 

 

 

I/O Controls

In addition to the voltage identification pins, several signals exist to control the DC-DC converter or to provide feedback from the converter to the CPU. These are Power-Good (PWRGD), Output Enable (OUTEN), and Upgrade Present (UP). These signals are discussed later.

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Contents Input Voltages Pentium Pro DC Power RequirementsIntroduction DC Voltage RegulationProcessor Voltage Identification Output Ripple and NoiseEfficiency ControlsRC5040 and RC5042 Controllers RC5040 and RC5042 DescriptionSimple Step-Down Converter Upgrade Present UP# Power Good PwrgdOutput Enable Outen Main Control LoopShort Circuit Protection Design Considerations and Component SelectionOver-Voltage Protection OscillatorRC5042 Thermal Mosfet SelectionTwo MOSFETs in Parallel Conditions1 Manufacturer & Model # Typ MaxCharge Pump or Bootstrap Mosfet Gate BiasConverter Efficiency Short Circuit Comparator Selecting the InductorImplementing Short Circuit Protection Resistor IRC Discrete MetalDescription ResistorResistor mΩ = 2000mi⋅ .2 = 0.74W RC5040 and RC5042 Short Circuit Current CharacteristicsFor each Mosfet Schottky Diode Selection Input filter Schottky Diode Selection TableOutput Filter Capacitors Bill of MaterialsMotorola Shottky Diode PCB Layout Guidelines and ConsiderationsPCB Layout Guidelines 320-6110Example of Proper MOSFETs Placements PC Motherboard Layout and Gerber FileApplication Note Debugging Your First Design Implementation TroubleshootingGuidelines for Debugging and Performance Evaluations Performance Evaluation Vout+ 80.0mV Device Description Iload =13.9ASummary RC5040/RC5042 Evaluation BoardAppendix a Directory of Component Suppliers Life Support Policy

RC5040, RC5042 specifications

The Fairchild RC5042 and RC5040 are versatile integrated circuits that stand out in the realm of high-performance analog applications. Designed to meet the demands of modern electronic systems, these devices integrate various features and technologies that contribute to their effectiveness in a multitude of applications.

The RC5040 is a precision voltage reference that offers a stable, low-noise output, making it ideal for applications such as instrumentation, data acquisition systems, and RF circuits. It boasts an operating temperature range of -40°C to +85°C, ensuring reliability in diverse environments. One of its most significant characteristics is its low-temperature drift, which minimizes variations in output voltage over temperature fluctuations, thereby enhancing the accuracy of devices that utilize it.

On the other hand, the RC5042 is designed as a high-speed comparator with an integrated voltage reference. This dual functionality allows for a more compact design in applications where space is a premium. The RC5042 features an ultra-fast response time and high input impedance, which contribute to its capability to handle rapidly changing signals without distortion. This makes it particularly useful in applications like analog signal processing and threshold detection.

Both devices utilize Fairchild's advanced BiCMOS technology, which combines the benefits of bipolar and CMOS processes. This technology allows the devices to operate with low power consumption while maintaining high speed and operational efficiency. The RC5042 and RC5040 also incorporate noise-reduction techniques, which help in minimizing unwanted disturbances that could impact circuit performance.

Another noteworthy characteristic of both the RC5040 and RC5042 is their ease of integration. They come in compact package sizes, making them easier to incorporate into various designs without compromising on performance. Furthermore, the availability of multiple output options allows engineers the flexibility to choose configurations that best suit their specific applications.

In conclusion, the Fairchild RC5042 and RC5040 are robust devices that offer essential functionality for various high-performance analog applications. With their precision, fast response time, and exceptional reliability, these integrated circuits are a valuable asset in the design of modern electronic systems, catering to the growing demands of the technology landscape.
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