Industrial

delta sigma adc bridge measurement techniques

This application note describes a method for accurately measuring the third order intercept point for low distortion IC products such as the LT5514. This includes the test setup, test equipment, test signal and interpretation of the measurement results.

ACPR (adjacent channel power ratio), AltCPR (alternate channel power ratio), and noise are important performance metrics for digital communication systems that use, for example, WCDMA (wideband code division multiple access) modulation. ACPR and AltCPR are both measures of spectral regrowth. The power in the WCDMA carrier is measured using a 5MHz measurement bandwidth. For ACPR, the total power in a 3.84MHz bandwidth centered at 5MHz (the carrier spacing) away from the center of the outermost carrier is measured and compared to the carrier power. The result is expressed in dBc. For AltCPR, the procedure is the same, except we center the measurement 10MHz away from the center of the outermost carrier. To measure ACPR and AltCPR, refer to the test setup shown in Figure 2. The DUT (device under test) is the LT5528, which is a high linearity direct I/Q modulator. It accepts WCDMA modulation at the baseband inputs, and generates a WCDMA modulated signal at the RF output. Note that a free running RF generator provides the LO signal. This type of generator is used because of its superior noise performance. This is critical, as a noisy LO signal may corrupt the modulator output, and consequently the ACPR measurement. For the generator shown, the automatic level control must be switched off to avoid degrading its broadband noise floor. Also,

This article discusses the application of linear regulators to post-regulate switching regulator outputs. Linear regulators offer benefits such as improved stability, accuracy, transient response, and lowered output impedance. However, they encounter difficulties in handling the ripple and spikes generated by switching regulators, particularly at higher frequencies. The article focuses on the impact of residual input-derived high-frequency components on the output of linear regulators.

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.

This document introduces Linear Technology's current sensing circuits

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.

This document describes the maximum electrical characteristics of a series of electronic devices, including nominal test maximum Zener current, maximum reverse impedance, maximum leakage current, etc. Each device has corresponding model, marking, and parameters.

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

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

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.

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

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.

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

The PBL 386 14/1 is a SLIC for use in ISDN Network Terminal Adapters and other short loop telecommunications equipment which often are remote powered, and by that, the available power is limited. The PBL 386 14/1 has been optimized for low total line interface cost, low power and requires a minimum of external components. The PBL 386 14/1 has constant current feed, programmable to max 30mA. The SLIC uses a first battery voltage for On-hook. A second battery voltage is used for Off-hook and must be connected, to reduce short loop power dissipation. The SLIC automatically switches between the two battery supply voltages without need for external components or external control. The loop current controls the switching between On-hook and Off-hook battery. The SLIC incorporates loop current, ground key and ring trip detection functions. The PBL 386 14/1 is compatible with loop start signalling. Two- to four-wire and four- to two-wire voice frequency (vf) signal conversion is accomplished by the SLIC in conjunction with either a conventional CODEC/filter or with a programmable CODEC/filter, e.g. SLAC, SiCoFi, Combo II. The programmable line terminating impedance could be complex or real to fit every market. Longitudinal voltages are suppressed by a feedback loop in the SLIC and the longitudinal balance specifica- tions meet Bellcore TR909 requirements. The PBL 386 14/1 package is a very PCB space efficient.