The AD210AN is the latest addition to a new generation of low-end, high-performance isolation amplifiers. This three-port, broadband isolation amplifier is fabricated using surface mount components in an automated assembly process.

The AD210AN combines design expertise with state-of-the-art manufacturing techniques to produce extremely compact and economical isolators with excellent performance and user-rich features far beyond those offered by more expensive devices.

The AD210AN provides complete isolation for the two to provide signal and power isolation through transformer coupling inside the module. The AD210AN features a fully functional design that operates from a single +15 V supply and does not require the use of an external DC/DC converter device unlike optocoupler isolation. A true three-port design structure allows the AD210AN to be used as an input or output isolator, single or multi-channel applications. The AD210 will maintain high performance under sustained common mode stress. Offering high accuracy and complete galvanic isolation, the AD210AN interrupts ground loops and leakage paths, and rejects common-mode voltages and noise that can degrade measurement accuracy from other devices. In addition, the AD210 protects various parts of the measurement system from malfunctioning that could lead to other failures.

Functional block diagram

Product Highlights

The AD210AN is a full-featured isolator that serves a wide range of users with benefits including:

High common-mode performance: The AD210AN provides 2500 V rms (continuous) and ± 3500 V peak (continuous) common-mode voltage isolation between any two ports. Capacitors 5 pF lower at the input yield 120 dB CMR at a gain of 100 , and low leakage current (2 μArmsmax @ 240 V rms, 60 Hz).

High accuracy: ±0.012% maximum nonlinearity (B. class), gain drift of ±25 ppm/°C max, input offset drift of (±10 ±30/G) μV/°C, AD210AN ensures signal integrity Sex provides a high level of isolation.

Wide Bandwidth: The AD210AN's full power bandwidth of 20 kHz makes it useful for wideband signals. It also works well in applications such as control loops, where limited bandwidth can lead to instability.

Small size: AD210AN provides complete isolation in a small DIP package as small as 1.00" x 2.10" x 0.350". Low

Profile DIP packages allow application to 0.5" card racks and assemblies. The pinout is optimized to facilitate board layout while maintaining isolation spacing between ports.

Three-Port Design: The AD210AN's three-port design structure allows each port (input, output, and power) to remain independent. This three-port design allows the AD210AN to be used as an input or output isolator. It also provides additional system protection should the power supply fail.

Isolated Power: The input can supply the output section of a ±15 V @ 5 mA voltage isolator. This feature allows the use of the AD210AN to excite floating signal conditioners, front-end amplifiers, and remote sensor and other circuit outputs at the input.

Flexible Input: An uncommitted op amp is available on the input. This amplifier provides the buffering and gain needed and facilitates many of the alternate input functions user requirements.

feature

High CMV isolation: 2500 V rms continuous

63500 V peak continuous

Small size: 1.00" 3 2.10" 3 0.350"

Three-port isolation: input, output and power

Low nonlinearity: 60.012% max

Wide bandwidth: 20 kHz full power (-3 dB)

Low Gain Drift: 625 ppm / 8C max

High CMR: 120 dB (G = 100 V/V)

Isolated Power: 615 V @ 65 mA

Uncommitted Input Amplifier

application

Multi-channel data acquisition

High Voltage Instrumentation Amplifier

Current Shunt Measurement

Process signal isolation

The basic block diagram of AD210AN is shown in the following figure. +15 V power is connected to the power port, and ±15 V isolated power is provided to the input and output ports through a 50 kHz carrier frequency. An uncommitted input amplifier can be used to provide gain or buffering of the input signal to the AD210. The full wave modulator converts the signal to the carrier frequency and applies it to the transformer T1. A synchronous demodulator in the output port reconstructs the input signal. One uses a 20 kHz, three-pole filter to minimize output noise and ripple. Finally, the output buffer provides a low level

The impedance output is capable of driving 2kΩ loads.

The AD210AN is very easy to use in a variety of applications. Powered by a single +15 V supply, the AD210AN will provide excellent performance when used as an input or output isolator, configured in single and multi-channel configurations.

Input Configuration: The basic unity-gain configuration for signals up to ±10 V is shown in Figure 2. Changes to other input amplifiers are shown in the data below. For smaller signal levels, Figure 3 shows how gain can be achieved while maintaining a very high input impedance.

The high input impedance 3 of the circuit above and below can be maintained in inverting applications. Since the AD210AN is a three-port isolator, either the input leads or the output leads can be interchanged to produce signal inversion.

The diagram below shows how to accommodate current input or sum current or voltage. This circuit configuration can also be used for signals greater than ±10 V. For example, a ±100 V input range can be handled with RF = 20kΩ and RS1 = 200kΩ.

When gain and offset adjustment is required, the actual circuit adjustment components will depend on the selected configuration of the input and whether the adjustment is made

Isolator input or output. Adjustments on the output side may use voltages that represent a dangerous adjustment period due to the presence of high common mode when the potentiometer on the input side is used. Offset adjustment is best at the input, as it is best to nullify the offset before gain.

The figure below shows the input conditioning circuit used when the input amplifier is configured in non-inverting mode. This cancellation regulation circuit injects a small voltage in series.

The low side of the signal source. This will not work if the source has another current path into the common or if current flows into the LO lead of the highway signal source. To minimize CMR degradation, keep the resistor series input LO below a few hundred ohms. The figure below also shows the preferred gain adjustment circuit. This circuit shows an RF of 50kΩ and can work for a gain of 10 or more. Adjustment becomes less effective at lower gains (its effect is halved at G=2), so the pot must be a larger portion of the total RF at low gains. At G=1 (follower) the gain input impedance cannot be adjusted down without compromising; it is better to adjust the gain or output of the source after.

The figure below shows the use of the input conditioning circuit when the input amplifier is configured in inverting mode. The offset adjustment makes the voltage at the summing node zero. This is better than current injection because it is less affected by subsequent gain adjustments. Gain adjustments are made in the feedback and are available for gains from 1 V/V to 100 V/V.

The figure below shows how the offset adjustment is made at the output through the offset floating output port. In this circuit, ±15 V. will be supplied by a single source. The output amplifier of the AD210AN is fixed to unity, so the output gain must be performed in subsequent stages.

Multi-channel data acquisition front end

Shown in the figure below is a four-channel data acquisition front end used to condition and isolate several common input signals found in various process applications. In this application, each AD210 will provide complete isolation from input to output as well as channel channels. By using isolators for each channel, maximum protection and rejection of unwanted signals are obtained. The three-port design allows the AD210AN to be configured as an input or output isolator. In this application the isolator is configured as an input device with a power port to provide additional protection against possible power failures.

Channel 1: AD210 is used to convert 4-20 mA current to cycle input signal to 0 V-10 V input. A 25Ω shunt resistor converts the 4-20 mA current into a +100 mV to +500 mV signal. The signal is offset by -100 mV through RO, producing a 0 mV to +400 mV input. The signal is amplified by a gain of 25 to produce the desired 0 V to +10 V output. An AD210AN with an open circuit will show -2.5 V at the output.

Channel 2: In this channel, the AD210 is used to condition and regulate the isolated current output temperature sensor, model AD590. At +25°C, the AD590 has a nominal current of 298.2µA. This current level will vary at a rate of 1 μA/°C. At -17.8°C (0°F), the AD590's current will drop by 42.8µA to +255.4µA. The AD580 reference circuit provides equal but opposite currents,

This results in zero net current flow, resulting in a 0 V output AD210. At +100°C (+212°F), the current output of the AD590 will be 373.2µA minus a bias current of 255.4µA The AD580 circuit will produce an input current of +117.8µA. This current is

Converted to voltage through RF and RG to produce an output of +2.12 V. Channel 2 will produce an output of +10 mV/°F 0°F to +212°F range.

Channel 3: Channel 3 is a high gain amplifier configured with a low level input channel for conditioning millivolt signals. With the input to the AD210 set to 1 and the input amplifier set to a gain of 1000, a ±10 mV input will produce ±10 V at the output of the AD210.

Channel 4: Channel 4 illustrates one possible configuration adjustment bridge circuit. The AD584 generates a +10 V voltage excitation voltage, while A1 inverts the voltage, resulting in a negative voltage excitation. A2 provides a gain of 1000 V/V to amplify low-level bridge signals. Additional gain can be obtained by reconfiguring the input amplifier of the AD210AN. ±VISS provides the complete power supply for this circuit without the need for a separate isolated excitation source.

Each channel is individually addressed by the multiplexer's channel select. Additional filtering or signal conditioning multiplexers should be followed, before the analog-to-digital conversion stage.