Introduction
Most analog engineers and system engineers have used or considered using AD devices at one time or another. The good new is they make good stuff. Sure, I also use many of the competitors but I can always rely on AD for good, state of the art analog components. Founded in 1965 Analog Devices Inc. Are world leaders in high performance signal processing and are synonymous with high performance and innovation among electronics manufacturers. Their diverse product portfolio covers Entertainment and Media, Industry and Aerospace, Medical Technology, Wireless and Automobiles Applications. Reference Design: Analog Devices The Digilent Pmod-AD6 is powered by the Analog Devices AD7091R, a a 12-bit successive approximation analog-to-digital converter (ADC) that offers ultralow power consumption (typically 349 µA at 3 V and 1 MSPS) while achieving fast throughput rates (1 MSPS with a 50 MHz SCLK). Avaya designs workplace devices and phones that enable and empower employees and increase their productivity and job satisfaction. Browse our devices today. Analog Devices had a line of micro-electromechanical systems (MEMS) microphones until it sold that business to InvenSense in 2013. Analog Devices MEMS microphones were found in smart phones, tablet PCs, security systems, and medical applications.
The highly integrated LT3491 provides a compact, simple solution for driving backlight circuits in battery-powered portable devices, such as cellular phones, PDAs, and portable GPS devices. It features internal compensation, open-LED protection, a 32V power switch and a 32V Schottky diode all inside a tiny SC70 package.
Specifically, the LT3491 is a fixed frequency step-up DC/DC converter that drives up to six white LEDs in series from a Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in uniform brightness without the need for ballast resistors. In addition, the 2.3MHz switching frequency allows the use of tiny inductors and capacitors.
Figure 1 shows how easy it is to drive six white LEDs from a Li-Ion battery. Figure 2 shows the efficiency of the six white LED application circuit.
High Side Sense
The LT3491 features a unique high side LED current sense that enables the part to function as a “one wire” current source—one side of the LED string can be returned to ground anywhere, allowing a simpler “one wire” LED connection. Traditional LED drivers use a grounded resistor to sense LED current requiring a 2-wire connection to the LED string. High side sense moves the sense resistor to the top of the LED string.
Figure 3 shows the advantage of high side sense in a cell phone where the LEDs are placed some distance away from the driver. The technique eliminates the return wire thereby reducing the number of wires running through the hinge. Also, it allows the LEDs to be placed further away from the converter without compromising performance.
Dimming & Shutdown Control
A single pin performs both shutdown and accurate LED dimming control. The dimming range of the part extends from 1.5V at the CTRL pin for full LED current down to 100mV. The CTRL pin directly controls the regulated sense voltage across the sense resistor that sets the LED current. Figure 4 shows the regulated sense voltage versus CTRL pin voltage.
In addition to using a DC voltage at the CTRL pin, either a filtered PWM signal or a direct PWM signal can be used to control the LED current. Direct PWM dimming achieves wider dimming compared to using a filtered PWM or a DC voltage. Direct PWM dimming uses a MOSFET in series with the LED string to quickly connect and disconnect the LED string. Figure 5 presents direct PWM dimming in a Li-Ion to four white LED application. The PWM signal controls both the turn on and turn off of the part through the CTRL pin and the MOSFET. Figure 6 shows the linearity of PWM dimming. The available dimming range depends on the settling time of the application and the PWM frequency used. The application in Figure 5 achieves a dimming range of 300:1 using a 100Hz PWM frequency. Figure 7 shows the available dimming range for different PWM frequencies.
Torch and Flash Mode LED Control
White LEDs are quickly gaining popularity as the illumination source for camera phones. White LEDs provide a simple compact solution for flash and torch lighting in cell phone applications. The LT3491 provides a small overall solution to flash and torch control.
Torch and flash applications typically use a single high power white LED. The LED driver cannot be setup as a boost because the input voltage in camera phones is very close to, if not higher, than the forward voltage of the LED. A higher input voltage creates a DC path to ground that will drain the battery. High side sensing allows the LT3491 to drive a single LED from higher inputs, thus avoiding this problem. Figure 8 shows the application circuit for torch and flash control powered from two Li-Ion cells. The voltage at the control pin can be moved between two DC levels to toggle between torch and flash operation.
Conclusion
The LT3491 provides a highly integrated solution to drive backlight applications up to six LEDs from a Li-Ion cell input with the added advantage of high side sense in a tiny SC70 package.
Analog Telephone Adapters (ATA)
Feature Access Codes
Older model phones and fax machines (that do not run on the internet) require a Business Digital Voice telephone line and an Analog Telephone Adapter (ATA) to work. An ATA easily converts existing older phone equipment from analog (Plain Old Telephone Service or POTS) to digital or VoIP systems.
This guide will cover the following topics related to ATA devices:
A. How do I install and connect analog devices to the ATA?
Several options for placing calls are presented on the UC-One Mobile. These functions can be used with the Communication Buttons, input a number to Dial for Voice or Video Calls by clicking the Call Pad Button.
- First, using a standard RJ-11 phone cable, connect your fax machine or analog phone to the PHONE 1 port on the ATA. Please note: To use the PHONE 1 or PHONE 2 port on your ATA, you must configure an additional station within the Admin Portal.
- Next, plug one end of the supplied Ethernet cable into the INTERNET port on the ATA. Plug the other end into your wall jack, LAN switch or other Ethernet connection to your router.
- Once complete, connect the power adapter to the power port and connect to the electrical outlet.
- The device is working if the Power, Internet, and/or Phone lights on the front of the device will be green. Please Note: The ETHERNET port on your ATA is NOT supported with the BDV service.
Your ATA is now ready for use and analog devices such as phones and fax machines are configured with the BDV service.
B. How do I answer a call from a cordless phone plugged into an ATA?
To answer a new call;
- Pick up the handset, press the Answer/Flash button or press speakerphone button (if your phone has a speakerphone option).
To answer while on another call (call waiting):
- Press Flash + 2 to retrieve a new incoming call after hearing the call waiting tone. The first call is automatically placed on hold.
- To alternate between the two calls, press Flash + 2.
To end a call:
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- Press the End button, hang up your handset or press the speakerphone button.
To put a call on Hold:
- If your phone has a Hold button, use it to put calls on or take off hold.
**If your phone does not have a Hold button:
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- Press Flash when on a call.
- The call is placed on hold and then hang up as soon as you hear the dial tone.
- To retrieve your held call, pick up the handset or press Speaker (if your phone has a speakerphone option). Please Note: If you have a call on hold, and receive a second call, you can alternate between the two calls by pressing Flash + 2.
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