ZXY-EI19 Hard-Pin Audio Isolation Transformer, EI19 DIP Through-Hole, Turns Ratio 1:1 / 1:5 / 1:11, Frequency 100 Hz-4.5 kHz, Withstand Voltage 500 V, Size 19.5 x 15 x 17 mm

1. Product Name

ZXY-EI19 is an EI19 hard-pin audio isolation and voice/data coupling transformer. DIP through-hole package, dimensions 19.5 x 15 x 17 mm, pin pitch 5 mm, turns ratio 1:1, 1:5 or 1:11 depending on model, frequency range 100 Hz to 4.5 kHz, Hi-POT withstand voltage 500 V, leakage current 1 mA for 60 seconds.

Overview. This series is designed around the same body and the same pin grid. The four models differ in their windings rather than their packaging, so a circuit board can be laid out once and populated with any turns-ratio variant as required by the circuit.

Physically, the device uses a laminated EI19 core, tape-wound coils on a black bobbin, with three terminals on the front terminal block and two terminals on the opposite edge. The core edges are left exposed, which makes the laminations clearly visible in photographs and allows inspection of the windings after assembly.

2. Features

Four variants in one package size. EI1901 and EI1902 are 1:1, EI1904 is 1:5, and EI1905 is 1:11, all sharing the same 19.5 × 15 × 17 mm body and the same 5 mm pin pitch.

100 Hz to 4.5 kHz. This is the operating band for voice and data coupling, and it is the specified operating range for these devices, not the full audio band.

Inductance specified as minimum values. EI1901 has 1.2 H on both windings, EI1902 has 585 mH on both windings, EI1904 has 2.9 H and 150 mH, and EI1905 has 266 mH and 17 H, all tested at 1 kHz with a 0.3 V signal.

DC resistance from 22 Ω. EI1901 measures 22 Ω and 28 Ω, while EI1905 reaches up to 1.58 kΩ on the secondary winding, all with a tolerance of ±15%.

Hi-POT 500 V on all models. A 1 mA leakage current limit is maintained for 60 seconds, with the same rating across the entire series.

Hard pins, DIP through-hole. Rigid terminals on a 5 mm pitch secure the device to the circuit board and allow standard soldering without a carrier.

High-isolation core. Laminated EI19 core with separated windings on the bobbin, with polarity brought out to the published schematic.

Yellow tape over the windings. The coils are wrapped in tape, while the core edges remain exposed for post-winding inspection.

Custom designs supported. Available from stock directly from the factory, with custom windings available on request.

The series parameters on the drawing deserve careful reading: turns ratios of 1:1, 1:5 and 1:11 are marked as "multiple options available," the maximum inductance of 1.2 H corresponds to EI1901, DC resistance is as low as 22 Ω, and Hi-POT withstands 500 V. These four values summarize the table in Chapter 5.

3. Advantages

Protects the front-end circuit. The transformer isolates input from output, so a downstream fault will not burn out the device output stage of the driving circuit.

Eliminates ground noise. Two separated windings cut the ground connection in the signal path, thereby eliminating AC hum caused by system grounds.

Balanced and unbalanced lines. The same device reduces external interference in both configurations.

One package size, four variants. Switching from 1:1 to 1:5 or 1:11 in a design requires no changes to pad layout, panel cutouts, or assembly drawings.

Rigid pins. Through-hole terminals suit standard soldering and easy replacement, without requiring re-qualification of carriers or reflow profiles.

Precision pin pitch. The 5 mm grid lets the device drop directly into existing DIP pad layouts, with no custom pad patterns required.

The pin grid is a practical advantage. The 5 mm pitch on a 19.5 mm body matches standard DIP pad layouts, so the device can replace competing parts on the same board without modification, and the four turns ratios mean the same version can serve both 1:1 isolation points and 1:11 coupling points.

4. Applications

The datasheet lists four application areas for this device.

Communication equipment. Line and voice circuits, for applications where two devices must not share a common ground.

Medical equipment isolation transformers. Signal paths that require signal exchange but must isolate the reference ground, used for isolation between medical equipment and patient circuits.

Telephone and fax equipment transformers. Used for line interface coupling, isolating electronic equipment from telephone lines, with an operating band of 100 Hz to 4.5 kHz.

Inductive (sensor) speaker transformers. Used to drive high-impedance inductive loads from low-impedance amplifier outputs.

In these applications, the core characteristic is the same: two circuits need to exchange signals but must not share a common reference ground. Telephone line interfaces, patient-side electrode circuits, and sensor speakers all sit on the outside of this isolation boundary.

5. Application Specifications

Electrical data is measured at 25°C and published per series. Inductance is a minimum value, measured at 1 kHz with a 0.3 V test signal; DC resistance tolerance is ±15%.

5.1 Electrical Specifications by Model

5.2 Construction and Mechanical Data

5.3 Terminals in the Published Schematic

6. Quality and Test Assurance

Each parameter below comes with its test condition. All models in the series share the same dielectric withstand rating, and the products carry CCC, CE and UL certification marks.