LINEAR Manuals

This Application Note describes a method to accurately measure internal and external phase and timing errors for a high performance direct I/Q modulator. A direct I/Q modulator, such as the LT5528, translates baseband I and Q signals to RF, and combines them to produce a modulated single sideband signal with (ideally) minimal residual carrier (LO feedthrough) and image signals (undesired sideband). In an ideal I/Q modulator, with perfect 90° phase shift between the I mixer and Q mixer local oscillators (LOI and LOQ), and with no other undesired phase and gain impairments, the modulator output will contain only the desired sideband. In practice, this is very difficult to accomplish. For example, with a requirement of –60dBc image suppression, the residual I-Q phase error is required to be below 0.16°. In practice, there are other sources of phase error, particularly in the baseband signal processing. Examples include baseband skew or other frequency dependent phase shifts in the modulator baseband circuitry; skew errors due to phase or delay mismatched baseband connection paths (e.g., cabling); and phase mismatch between the I and the Q paths in the baseband signal source (e.g., baseband DACs or signal generators.). These phase errors can cause RF output spectra to be shaped like those shown in Figures 1, 2 and 3.

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This document introduces Linear Technology's current sensing circuits

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This application note presents the thermal model of LTM4600 DC/DC μModule regulator. The model includes thermal resistance from junction to top surface, from top surface to ambient, and the double-sided cooling scheme.

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This application note introduces the features and applications of the LTC4411-4414 switch mode power supply monitors.

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This document discusses the testing and evaluation of voltage regulators under transient loads, as well as practical considerations in testing.

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This document introduces the LTC®1966/LTC1967/LTC1968 family, which is a Sigma-Delta based RMS-to-DC converter with high accuracy and wide bandwidth.

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This document mainly introduces how to use Schottky diodes to measure battery stack voltage.

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This application note illustrates how to interface RF I/Q modulators with several popular D/A converters, and introduces the circuits required for the interface to maximize voltage transfer from the DAC to the baseband inputs of the modulator, as well as provide some reconstruction filtering.

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Introduces the thermal design of LTM4601 DC/DC μModule regulator, including thermal model and temperature rise analysis with/without a heatsink.

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This application note introduces the LTC3207/LTC3207-1 LED/Camera driver, which can drive 12 ULEDs and one camera flash LED. The 12 ULEDs can be individually turned on or off, set to general purpose output (GPO) mode, set to blink or fade. The driver also has an external enable (ENU) pin that can be used to blink, fade or turn on/off the LEDs.

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AN111-1 is an application note about LTC3219 LED driver, introducing its features and characteristics.

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This application note describes a DC/DC converter that runs from a low input voltage, such as a lithium ion battery. The input voltage range is from 0.3V to 1.6V.

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This document illustrates how to program and use the unique features of the LTC3220/LTC3220-1 Universal LED (ULED) Driver, including individually controlling, gradually turning on and off, or blinking up to 18 LEDs. This device may also be used to provide digital signal(s) to other devices while in shutdown.

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This document describes a transformer originally intended for LCD display backlight service. The transformer provides a high voltage, low current stable output, and has low noise characteristics.

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This application note provides PCB layout design guidelines for the LTM80xx series μModule regulators, including input and output routing, power and ground connections, and component placement.

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The document describes the thermal performance of Linear Technology's μModule 4-channel 1.5 V 48 A power module. Experimental results show that the temperature of the μModule module exhibits a significant difference when different heat dissipation methods are used. The experimental results show that 200 LFM airflow can reduce the temperature of the module by 20 °C.

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This document describes a new module voltage regulator system for power supplies, which can provide efficient and stable power output in a small, low-profile form factor. It is suitable for applications that require high power output. The system has a simple design and installation process, and has lower system costs and power consumption.

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AN122-1 is an application note on diodes, which introduces diode turn-on time, overvoltage and overvoltage protection.

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This application note describes how to measure the noise performance of voltage references. The note provides detailed schematics and circuit diagrams of the measurement system and provides instructions on the noise testing method.

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Application Note 123 introduces the LTC6400 differential amplifier/ADC driver and provides design optimization recommendations for low distortion, low noise, gain and power options, input considerations, dynamic range and output networks, stability, and layout considerations.

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