Power Circuits for Instrumentation

The ADP5071 is a dual high performance dc-to-dc regulator that generates independently regulated positive and negative rails.

The input voltage range of 2.85 V to 15 V supports a wide variety of applications. The integrated main switch in both regulators enables generation of an adjustable positive output voltage up to +39 V and a negative output voltage down to −39 V below input voltage.

The ADP5071 operates at a pin selected 1.2 MHz/2.4 MHz switching frequency. The ADP5071 can synchronize with an external oscillator from 1.0 MHz to 2.6 MHz to ease noise filtering in sensitive applications. Both regulators implement programmable slew rate control circuitry for the MOSFET driver stage to reduce electromagnetic interference (EMI).

Flexible start-up sequencing is provided with the options of manual enable, simultaneous mode, positive supply first, and negative supply first.

The ADP5071 includes a fixed internal or resistor programmable soft start timer to prevent inrush current at power-up. During shutdown, both regulators completely disconnect the loads from the input supply to provide a true shutdown.

Other key safety features in the ADP5071 include overcurrent protection (OCP), overvoltage protection (OVP), thermal shutdown (TSD), and input undervoltage lockout (UVLO).

The ADP5071 is available in a 20-lead LFCSP or in a 20-lead TSSOP and is rated for a −40°C to +125°C junction temperature range.

Applications

• Bipolar amplifiers, ADCs, DACs, and multiplexers
• Charge-coupled device (CCD) bias supply
• Optical module supply
• RF power amplifier (PA) bias

The ADuM6000 is an isolated DC/DC converter based on the Analog Devices, Inc., iCoupler^® technology. The DC/DC converter in this device provides regulated, isolated power in several combinations of input and output voltages as listed in Table 1 on the data sheet. The Analog Devices chip scale transformer iCoupler technology transfers isolated power in this DC/DC converter with up to 31% efficiency. The result is a small form factor, total isolation solution. Higher output power levels are obtained by using the ADuM6000 to augment the power output of the ADuM5401, ADuM5402, ADuM5403, ADuM5404, ADuM520x, and ADuM620x iCouplers with isoPower^®. isoPower^® uses high frequency switching elements to transfer power through its transformer. Special care must be taken during printed circuit board (PCB) layout to meet emissions standards. See the AN-0971 Application Note for board layout recommendations.

Applications

• USB peripheral power
• RS-232/RS-422/RS-485 transceiver power
• Industrial field bus power
• Power supply start-up bias
• Industrial PLCs

The ADP7118 is a CMOS, low dropout (LDO) linear regulator that operates from 2.7 V to 20 V and provides up to 200 mA of output current. This high input voltage LDO is ideal for the regulation of high performance analog and mixed-signal circuits operating from 20 V down to 1.2 V rails. Using an advanced proprietary architecture, the device provides high power supply rejection, low noise, and achieves excellent line and load transient response with a small 2.2 µF ceramic output capacitor. The ADP7118 regulator output noise is 11 μV rms independent of the output voltage for the fixed options of 5 V or less.

The ADP7118 is available in 16 fixed output voltage options. The following voltages are available from stock: 1.2 V (adjustable), 1.8 V, 2.5 V, 3.3 V, 4.5 V, and 5.0 V.

Additional voltages available by special order are 1.5 V, 1.85 V, 2.0 V, 2.2 V, 2.75 V, 2.8 V, 2.85 V, 3.8 V, 4.2 V, and 4.6 V.

Each fixed output voltage can be adjusted above the initial set point with an external feedback divider. This allows the ADP7118 to provide an output voltage from 1.2 V to V_IN − V_DO with high PSRR and low noise.

User programmable soft start with an external capacitor is available in the LFCSP and SOIC packages.

The ADP7118 is available in a 6-lead, 2 mm × 2 mm LFCSP making it not only a very compact solution, but it also provides excellent thermal performance for applications requiring up to 200 mA of output current in a small, low profile footprint. The ADP7118 is also available in a 5-lead TSOT and an 8-lead SOIC.

Applications

• Regulation to noise sensitive applications
  – ADC and DAC circuits, precision amplifiers, power for VCO V_TUNE control
• Communications and infrastructure
• Medical and healthcare
• Industrial and instrumentation
• Supported by ADIsimPower tool

The ADP7182 is a CMOS, low dropout (LDO) linear regulator that operates from −2.7 V to −28 V and provides up to −200 mA of output current. This high input voltage LDO is ideal for regulation of high performance analog and mixed signal circuits operating from −27 V down to −1.2 V rails. Using an advanced proprietary architecture, it provides high power supply rejection and low noise, and achieves excellent line and load transient response with a small 2.2 μF ceramic output capacitor.

The ADP7182 is available in fixed output voltage and an adjustable version that allows the output voltage to range from −1.22 V to −V_IN + V_DO via an external feedback divider.

The following fixed output voltages are available from stock: −5 V (3 mm × 3 mm LFCSP), −1.8 V, −2.5 V, −3 V, −5 V (TSOT), −1.2 V, −1.5 V, −2.5 V, −5 V (2 mm × 2 mm LFCSP). Additional voltages are available by special order.

The ADP7182 regulator output noise is 18 μV rms independent of the output voltage. The enable logic is capable of interfacing with positive or negative logic levels for maximum flexibility.

The ADP7182 is available in 5-lead TSOT, 6- and 8-lead LFCSP packages for a small, low profile footprint.

Applications

• Regulation to noise sensitive applications
  • Analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuits, precision amplifiers
• Communications and infrastructure
• Medical and healthcare
• Industrial and instrumentation

The ADP7185 is a complementary metal oxide semiconductor (CMOS), low dropout (LDO) linear regulator that operates from −2.0 V to −5.5 V and provides up to −500 mA of output current. This high output current LDO is ideal for regulation of high performance analog and mixed signal circuits operating from −0.5 V down to −4.5 V. Using an advanced proprietary architecture, the ADP7185 provides high power supple rejection ratio (PSRR) and low noise, and it achieves excellent line and load transient response with a small 4.7 μF ceramic output capacitor.

The ADP7185 is available in 15 fixed output voltage options. The following voltages are available from stock: −0.5 V, −1.0 V, −1.2 V, −1.5 V, −1.8 V, −2.0 V, −2.5 V, −3.0 V, and −3.3 V.

Additional voltages available by special order are −0.8 V, −0.9 V, −1.3 V, −2.8 V, −4.2 V, and −4.5 V. An adjustable version is also available which allows output voltages that range from −0.5 V to −V_IN + 0.5 V with an external feedback divider.

The enable logic feature is capable of interfacing with positive or negative logic levels for maximum flexibility.

The ADP7185 regulator output noise is 4 μV rms independent of the output voltage. The ADP7185 is available in an 8-lead, 2 mm × 2 mm LFCSP, making it not only a very compact solution but also providing excellent thermal performance for applications requiring up to −500 mA of output current in a small, low profile footprint.

Applications

• Regulation to noise sensitive applications: analog-to-digital converters (ADCs), digital-to-analog converters (DACs), precision amplifiers
• Communications and infrastructure
• Medical and healthcare
• Industrial and instrumentation

The circuit, shown in Figure 1, is an H-bridge composed of high power switching MOSFETs that are controlled by low voltage logic signals. The circuit provides a convenient interface between logic signals and the high power bridge. The bridge uses low cost N-channel power MOSFETs for both the high and low sides of the H-bridge. The circuit also provides galvanic isolation between the control side and power side. This circuit can be used in motor control, power conversion with embedded control interface, lighting, audio amplifiers, and uninterruptable power supplies (UPS).

Modern microprocessors and microconverters are generally low power and operate on low supply voltages. Source and sink current for 2.5 V CMOS logic outputs ranges from μA to mA . Driving an H-bridge switching 12 V with a 4 A peak current requires the use of carefully selected interface and level translation components, especially if low jitter is needed.

 

The ADG787 is a low voltage CMOS device that contains two independently selectable single-pole double-throw (SPDT) switches. With a 5 V dc power supply, a voltage as low as 2 V is a valid high input logic voltage. Therefore, the ADG787 provides appropriate level translation from the 2.5 V controlling signal to the 5 V logic level needed to drive the ADuM7234 half-bridge driver.

The ADuM7234 is an isolated, half-bridge gate driver that employs Analog Devices’ iCoupler^® technology to provide independent and isolated high-side and low-side outputs making it possible to use N-channel MOSFETs exclusively in the H-bridge. There are several benefits in using N-channel MOSFETs: N-channel MOSFETs typically have one third of the on resistance of P-channel MOSFETs and higher maximum current; they switch faster, thereby reducing power dissipation; and the rise time and fall time is symmetrical.

The 4 A peak drive current of the ADuM7234 ensures that the power MOSFETs can switch on and off very fast, thereby minimizing the power dissipation in the H-bridge stage. The maximum drive current of the H-bridge in this circuit can be up to 85 A, which is limited by the maximum allowable MOSFET current.

The ADuC7061 is a low power, ARM7 based precision analog microcontroller with integrated pulse width modulated (PWM) controllers that have outputs that can be configured to drive an H-bridge after suitable level translation and conditioning.

 

Figure 1. H-Bridge Using ADuM7234 Isolated Half-bridge Driver (Simplified Schematic: All Connections and Decoupling Not Shown)

The circuit shown in Figure 1 is an isolated, flyback power supply that uses a linear isolated error amplifier to supply the feedback signal from the secondary side to the primary side. Unlike optocoupler-based solutions, which have a nonlinear transfer function that changes over time and temperature, the linear transfer function of the isolated amplifier is stable and minimizes offset and gain errors when transferring the feedback signal across the isolation barrier.

The entire circuit operates from 5 V to 24 V, allowing it to be used with standard industrial and automotive power supplies. The output capability of the circuit is up to 1 A with a 5 V input and 5 V output configuration.

This solution can be adapted for use in applications where higher dc input voltages are used to create lower voltage isolated supplies with good efficiency and a small form factor. Examples include 10 W to 20 W telecommunication and server power supplies, where power efficiency and printed circuit board (PCB) density are important, and −48 V supplies are common.

Figure 1. Simplified Schematic of Flyback Power Supply Circuit