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Preet Sibia
Preet Sibia has over 12 years of experience in the semiconductor industry, at Maxim Integrated Products and National Semiconductor. He has worked in roles such as an Applications Engineer, Applications Manager, FAE and Business Development Manager with a focus on analog and mixed-signal products. Over the years, Preet has directly supported products ranging from high-speed interconnect (SERDES), ADCs, DACs, temperature sensors, LED drivers, and DC-DC power management devices.
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Hi Tony,
National has several new products in the power management space covering the gamut of powering digital circuits such as FPGAs and uP to the power management of HB-LEDs used in illumination applications.
A new part to consider for powering FPGAs such as Cyclone III or Cyclone IV is the LM26480 quad output regulator, which features two switching regulators for powering Core and I/O voltages and two LDOs for powering more noise sensitive supplies such as high-speed transcievers and clocks.
http://www.national.com/pf/LM/LM26480.html
For HB-LED lighting applications one of the latest devices is the LM3424. The LM3424 is a very versatile N-channel MosFET controller for LED drive and can be easily configured in buck, boost, buck-boost, and SEPIC topologies. Additionally, the LM3424 includes a thermal foldback feature for temperature management of the LEDs and a high input voltage rating of 75V. The LM3423 is an ideal choice for illuminating LEDs in a wide variety od applications. The LM3424 is also fully Webench enabled allowing customers to create a full design using the LM3424 with their preferred LEDs and to run full simulations on the device performance.
http://www.national.com/pf/LM/LM3424.html
Thanks,
Preet
hello Sir
I am an engineering student from india ,
i am looking for certain components for my engineering college project
a) anolog to 8 bit digital converters
pleasehelp me out i would be looking farwardfor u r reply
Hello,Preet:
When I select Serdes products,pls confirm if I need calculate wire impedance or cable impedance.have any reference in National web? or do you have any suggestions?
thanks
kemmi
...from Preet
Hello Lakshmi,Thank you for your request. I understand you are looking for an 8-bit ADC. National Semiconductor (NSC) has a wide portfolio of 8-bit ADCs covering sampling rates from 50KSPS-1MSPS, 1MSPS-200MSPS, and ultra-high speed 500MSPS-3GSPS. NSC has an ADC to address almost any application. To assist you with a selection, I am going to need more information on your project including the signals you are sampling, voltages available in your system, and what type of interface you have available to read the ADC (SPI, I2C). A good place for you to start the selection process is visiting NSC's ADC homepage at: http://www.national.com/analog/adcThis site provides an overview of all of NSC's available 8-bit ADCs. Regards, Preet
...from Preet
Hello Kemmi,
Thank you for your question. The answer to your question is very much dependent on the type of SERDES you are using, the length and type of cable, and what data rate you are trying to achieve. Many serializers have LVDS output buffers and deserializers accept LVDS differential inputs. The differential impedance of the transmission medium should be about 100ohm and be terminated with a matched termination resistor physically close to the input of the deserializer. You could use 100ohm CAT5 cable for these types of applications. A useful reference for designing with high-speed differential signals in National’s LVDS Owner’s manual available at the following link:
http://www.national.com/analog/interface/lvds_owners_manual
Regards, Preet
Hello Preet
Thanks your reply. and now there are so many IC that can output LVDS signal .eg:A/D converter / FPGA I/O output...
so these LVDS signal have any different between special LVDS IC and A/D converter / FPGA I/O output ? in design, which proceeding we need take care of ?
thanks
kemmi
...from Preet
Hello Kemmi,
Yes there are a number of devices that have LVDS outputs. The LVDS standard defined under ANSI/TIA/EIA-644-A is an electrical standard only defining driver output characteristics and receiver input characteristics. Guidelines are also given on bus configuration, cables, and termination. Protocol, connectors, and bus structure are not defined in this standard, as they are application dependent.
Therefore, devices that have standard LVDS outputs should be able to communicate with other devices that accept LVDS inputs. There are cases such as SERDES which can have proprietary encoding schemes where a matched Serializer and Deserializer pair is required to complete the communication. For cases such as these, NSC puts the matched SERDES on the same datasheet.
The following are some basic recommendations to follow when designing with LVDS devices:
a) Use at least 4 PCB board layers (top to bottom): LVDS signals, ground, power, TTL signals. Dedicating planes for VCC and Ground are typically required for high-speed design. A solid ground plane is required to establish a controlled (known) impedance for the transmission line interconnects. Narrow spacing between power and ground planes will also create an excellent high frequency bypass capacitance.
b) Isolate fast edge rate CMOS/TTL signals from LVDS signals, or they may couple crosstalk onto the LVDS lines. It is best to put TTL and LVDS signals on a different layer(s) which should be isolated by the power and ground planes.
c) Keep drivers and receivers as close to the (LVDS port side) connectors as possible. This helps to ensure that the differential lines do not pick up noise generated from the board, which can result in higher EMI. This recommendation also helps to minimize skew between the lines.
d) Bypass each LVDS device and also use distributed bulk capacitance. Surface mount capacitors placed close to power and ground pins work best.
e) Power and ground traces should be wide (low impedance) traces. Do not use 50
Ω design rules for power and ground traces. Their function is to be a low impedance path. f) Keep ground PCB return paths short and wide. Provide paths that create the smallest return loop for image currents. g) Systems connected through cables should provide a common ground wire between the systems. This provides a short known path for common-mode currents to return. h) Use two vias to connect bypass capacitor pads to power and ground planes. This minimizes inductance effects. Surface mount capacitors are recommended since they are compact and can be located close to device pins. Regards, Preet
Hello Preet
I am constructing a visual light communication system for indoor communication. My transmitter is an RGB LED panel (50 LEDs for now am planning to make a bigger panel) mounted on the ceiling and serial data is modulated onto the LED light. The three colors in the LED are for creating three communication channels that can be separated by the use of color filters at the receiver. The receiver is placed at the table top about 2 m from the ceiling. I had been using a photo transistor that is part of a photo interruptor at the receiver side and displaying the data onto a computer. It is working fine upto 28800 bps but only after the light is focused by the use of a convex lens onto the detector so difficult when the receiver is mobile.
I need a detector (photo diode or photo transistor whichever is better) that can give me some freedom in movement, the data rate of at least 14400 bps is enough for me. Could you suggest me a better option ?
Natasha
P.S. The area of movement is round about a square of side 200 cm.
from Preet...
Hi Natasha,
Thank you for your question. This looks like a very cool application. I have very limited experience with photo detector selection, but can point you in the right direction to help select the appropriate device. In the past, I have used some photo diodes from Silicon Sensor:
http://www.silicon-sensor.com/index.php. They can be a good starting point. Additionally, on Element14 there are 2 experts for Sensor and Optoelectronics that should be able to offer excellent insight on adding the freedom of movement for your design. Ken Nishamura:
http://www.element-14.com/community/people/kazunishi
Orlando Diaz:
http://www.element-14.com/community/people/Orlando_Diaz%20
National Semiconductor does offer a WEBENCH Sensor Designer tool that helps create the complete analog front end (AFE) to condition the sensor output for processing. The tool allows you to take the specifications of whichever sensor you end up using and create a customer AFE circuit. The WEBENCH tool is available off of National Semiconductor's homepage
www.national.com on the right side of the page "WEBENCH DESIGNER" under sensors. Regards, Preet
Thank u so much for pointing me into the right direction. I am going to contact the people u referred me to.
Best Regards
Natasha
