feature

Low power operation; 5V operation; 1.0mA max per channel @0 Mbps to 2 Mbps 3.5mA max per channel @10 Mbps; 31mA max per channel @90 Mbps; 3V operation; 0.7mA max per channel @0 Mbps to 2 Mbps 2.1 mA max @10 Mbps per channel; 20 mA max @ 90 Mbps per channel; bidirectional communication; 3V/5V level shifting; high temperature operation: 105°C; high data rate: dc to 90 Mbps ( NRZ); precise timing characteristics; maximum 2 ns pulse width distortion; 2 ns maximum channel-to-channel matching; high common-mode transient immunity: >25kv/μs; output enable function; wide body 16 lead SOIC package, lead-free version available ; Safety and Regulatory Approvals; UL Listed: 2500 V rms, 1 minute per UL 1577; CSA Component Acceptance Notice #5A; VDE Certificate of Conformity; German Industrial Standard EN 60747-5-2 (VDE 0884 Part 2): 2003-01 ; German Industrial Standard EN 60950 (VDE 0805): 2001-12; European Industrial Standard EN 60950: 2000; VIORM=560V peak.

application

General purpose multi-channel isolation; SPI® interface/data converter isolation; RS-232/RS-422/RS-485 transceivers; industrial fieldbus isolation.

General Instructions

The ADuM140x are 4-channel digital isolators based on analog device iCoupler® technology. Combined with high-speed CMOS and monolithic air-core transformer technology, these isolation components offer superior performance over alternatives such as optocouplers.

By avoiding the use of LEDs and photodiodes, iCoupler devices eliminate the design difficulties typically associated with optocouplers. With a simple digital interface and stable performance characteristics, the typical problems of current transfer ratio uncertainty, nonlinear transfer function, temperature and lifetime effects are eliminated. These iCoupler products eliminate the need for external drivers and other discrete items. Furthermore, at comparable signal data rates, i-coupler devices consume one-tenth to one-sixth the power of an optocoupler.

The ADuM140x isolators provide four independent channels of isolation in various channel configurations and data rates (see ordering guide). All models operate from supply voltages from 2.7 V to 5.5 V, providing compatibility with low-voltage systems and enabling voltage translation across the isolation barrier. In addition, the ADuM140x offers low pulse width distortion (CRW level <2ns) and tight channel matching (CRW level <2ns). Unlike other optocoupler replacements, the ADuM140x isolators feature a patented refresh feature that ensures DC correctness without input logic transitions and power up/down conditions.

Typical performance characteristics

application information

PC board layout

The ADuM140x digital isolators do not require external interface circuitry for logic interfaces. Power supply bypassing at the input and output power pins is strongly recommended (Figure 17). Bypass capacitors are most conveniently connected between pins 1 and 2 for V and between pins 15 and 16 for V. The capacitor value should be between 0.01µF and 0.1µF. The total lead length between the ends of the capacitor and the input power pins should not exceed 20 mm. Also consider bypassing between pins 1 and 8 and between pins 9 and 16, unless the ground pair on each package side is connected near the package.

In applications involving high common mode transients, care should be taken to ensure that plate coupling on the isolation barrier is minimized. Additionally, the board layout should be designed so that any coupling that occurs will have the same effect on all pins on a given component side. Failure to ensure this could cause voltage differences between pins to exceed the absolute maximum ratings of the device, resulting in latch-up or permanent damage.

Propagation delay related parameters

Propagation delay is a parameter that describes the time it takes for a logic signal to travel through a component. The propagation delay to a logic low output may differ from the propagation delay to a logic high output.

Pulse width distortion is the largest difference between these two propagation delay values and is an indication of how accurately the timing of the input signal is maintained.

Channel-to-channel matching refers to the maximum difference in propagation delay between channels within a single ADUM140X component.

Propagation delay skew is the maximum value of the propagation delay between multiple ADUM140X components operating under the same conditions.

DC Correctness and Magnetic Field Immunity

Positive and negative logic transitions at the input of the isolator cause narrow pulses (~1ns) to be sent through the transformer to the decoder. The decoder is bistable, so it can be set or reset with a pulse, indicating input logic transitions. In the absence of more than 2 μs logic transitions at the input, a periodic set of refresh pulses indicating the correct input state is sent to ensure dc correctness at the output. If the decoder does not receive internal pulses for more than about 5 microseconds, it is assumed that the input side has no power or functionality, in which case the isolator output is forced to the default state by a watchdog timer circuit.

The magnetic field immunity limit of the ADuM140x is set by the condition that the induced voltage in the receiver coil of the transformer is large enough to incorrectly set or reset the decoder. The following analysis defines the conditions under which this may occur. Check the 3V operating condition of the ADuM140x as it represents the most susceptible operating mode.

The pulse amplitude at the transformer output is greater than 1.0V. The decoder's sensing threshold is about 0.5V, so a 0.5V margin is established in which the induced voltage can be tolerated. The voltage induced by the receiver coil is given by:

where: β is the magnetic flux density (Gaussian). N is the number of turns of the receiving coil. r is the radius (cm) of n turns in the receive coil.

Given the geometry of the receiver coil in the ADUM140X and the imposed requirement of a maximum 0.5 V margin for the induced voltage in the decoder, calculate the maximum allowable magnetic field as shown in Figure 19.

For example, at a magnetic field frequency of 1 MHz, a maximum allowable magnetic field of 0.2 kGauss induces a voltage of 0.25 volts on the receiving coil. This is about 50% of the sensing threshold and will not cause false output transitions. Similarly, if such an event occurs during the transmit pulse (and has the worst polarity), reduce the received pulse from >1.0v to 0.75v - still well above the decoder's 0.5v sensing threshold.

The flux density values above correspond to specific current amplitudes at a given distance from the ADuM140x transformer. Figure 20 presents these allowable current amplitudes as a function of frequency for selected distances. As shown, the ADuM140x is extremely immune and can only be affected by very high currents at high frequencies, very close to the components. For the 1 MHz example noted, a 0.5 kA current must be placed 5 mm from the ADuM140x to affect the operation of the component.

Note that under the combination of strong magnetic fields and high frequencies, any loops formed by the printed circuit board traces may generate enough error voltages to trigger the thresholds of subsequent circuits. Care should be taken to avoid this possibility when laying out such traces.

Power consumption

The supply current on a given channel of the ADuM140x isolator is a function of supply voltage, channel data rate, and channel output load.

For each input channel, the supply current is given by:

For each output channel, the supply current is given by:

where: IDDI(D), IDDO(D) are the input and output dynamic supply current per channel (mA/Mbps). CL is the output load capacitance (pF). VDDO is the output supply voltage (V). f is the input logic signal frequency (MHz, half rate of input data, NRZ signal). fr is the input stage refresh rate (Mbps). IDDI(Q), IDDO(Q) are the specified input and output quiescent supply currents (mA).

To calculate the total supply current for IDD1 and IDD2, the current corresponding to each input and output channel of the power supply is calculated and summed for IDD1 and IDD2. Figures 8 and 9 provide per-channel supply current as a function of data rate for unloaded output conditions. Figure 10 provides the 15 pF over-channel supply current output condition as a function of data rate. Figures 11 through 14 provide the total IDD1 and IDD2 supply current as a function of data rate for the ADuM1400/ADuM1401/ADuM1402 channel configuration.

Dimensions