SI8421AD-D-IS - 5kV 2-Channel Digital Isolator 1Mbps | Silicon Labs
N.º de pieza: SI8421AD-D-IS ✓ Activo| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $3.2 | $3,20 |
| 10 | $2.86 | $28,60 |
| 100 | $2.45 | $245,00 |
| 500 | $2.05 | $1.025,00 |
| 1.000 | $1.72 | $1.720,00 |
SI8421AD-D-IS Descripción general
A digital isolator is a semiconductor device that transfers logic-level signals across an isolation barrier using on-chip RF-coupled or capacitive-coupled isolation channels instead of optocouplers or transformers. Digital isolators belong to the isolation IC hierarchy: isolator -> interface IC -> signal chain IC -> semiconductor. Compared to legacy optocouplers, CMOS digital isolators offer 10x higher reliability, lower propagation delay, lower power consumption, smaller footprint, and stable parametric performance over temperature and aging.
Key features of the SI8421AD-D-IS include Schmitt-trigger inputs for noisy industrial environments, 5 kVrms safety isolation certified by UL, CSA, and VDE, and reinforced insulation rating when used in wide-body SOIC. The device consumes approximately 1.8 mA per channel at 1 Mbps, supports 2.7 V to 5.5 V supply on both VDD1 and VDD2 rails, and operates across the -40 C to +125 C industrial temperature range. The wide-body SOIC-16 package provides 7.5 mm of creepage distance per IEC 60601 / IEC 60747-17 requirements for reinforced insulation.
The Si8421 family uses Silicon Labs' proprietary RF-coupled isolation technology, embedding an RF carrier across two capacitive isolation capacitors on each die. This architecture eliminates the LED aging and current-transfer-ratio degradation inherent to optocouplers and achieves typical CMTI performance an order of magnitude above opto-based solutions. The wide-body SOIC package provides the reinforced creepage distance required for 5 kV reinforced insulation in industrial, renewable-energy, and medical systems.
Typical applications include isolated SPI/UART interfaces in motor drives, isolated gate-drive signal paths in industrial inverters, isolated data acquisition front-ends, isolated power-supply feedback, and isolated serial communication between MCU and high-voltage subsystems. The 5 kV rating suits 480 Vac industrial bus systems and 600 V solar inverter signal chains where reinforced insulation is mandated.
When designing with this device, place 0.1 uF bypass capacitors close to each VDD pin and minimize trace capacitance on the input/output side. The two channels are unidirectional and identically configured; if bidirectional signaling is needed across the same isolation barrier, choose a Si8421 (1 forward + 1 reverse) variant or pair two Si8421AD-D-IS devices in opposing directions. The default-high or default-low output behavior under input power loss must match the system-level fail-safe state.
This page synthesizes distributor pricing, parametric drop-in alternatives from the same Si84xx family and cross-brand equivalents, and practical isolation design notes not found in the manufacturer datasheet alone.
Alternativas directas para SI8421AD-D-IS — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
SI8421AD-B-IS
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
SI8421AB-D-IS
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
SI8421AD-D-IS-R
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
ISO7221ADR
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
ISO7221MDR
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
SI8421AD-D-IS Especificaciones
| Isolation Voltage (Withstand) | 5000 Vrms |
| Number of Channels | 2 |
| Channel Directionality | 2 forward (unidirectional) |
| Maximum Data Rate | 1 Mbps |
| Maximum Propagation Delay | 35 ns |
| Common-Mode Transient Immunity (CMTI) | 20 kV/us (minimum) |
| Supply Voltage (VDD1, VDD2) | 2.7 V to 5.5 V |
| Fail-Safe Output State | Default LOW (D option) |
| Supply Current per Channel at 1 Mbps | 1.8 mA (typical) |
| Rango de temperatura de funcionamiento | -40 C to +125 C |
| Encapsulado | 16-SOIC wide-body (0.295 inch / 7.50 mm width) |
| Creepage Distance | 7.5 mm |
| Tipo de montaje | Surface Mount |
| Safety Certifications | UL, CSA, VDE (reinforced insulation in wide-body SOIC) |
| Estado RoHS | Compliant |
Configuración de pines de SI8421AD-D-IS
| Pin 1 | VIA — Input A, side 1 (channel 1 input) |
| Pin 2 | GND1 — Ground reference for side 1 |
| Pin 3 | VDD1 — Supply for side 1 (2.7 V to 5.5 V) |
| Pin 4 | VDD2 — Supply for side 2 (2.7 V to 5.5 V) |
| Pin 5 | GND2 — Ground reference for side 2 |
| Pin 6 | VOA — Output A, side 2 (channel 1 output) |
| Pin 7 | NC — Not connected (per datasheet) |
| Pin 8 | NC — Not connected (per datasheet) |
| Pin 9 | VOB — Output B, side 2 (channel 2 output) |
| Pin 10 | GND2 — Ground reference for side 2 (second pin) |
| Pin 11 | VDD2 — Supply for side 2 (second pin) |
| Pin 12 | GND2 — Ground reference for side 2 (third pin) |
| Pin 13 | VIB — Input B, side 1 (channel 2 input) |
| Pin 14 | NC — Not connected (per datasheet) |
| Pin 15 | GND1 — Ground reference for side 1 (second pin) |
| Pin 16 | VDD1 — Supply for side 1 (second pin) |
Aplicaciones típicas
SI8421AD-D-IS es adecuado para 6 aplicacións: Isolated SPI / UART in Industrial Motor Drives, Isolated Gate-Drive Signal Path for SiC/GaN Inverters, Isolated Data Acquisition Front-End, Isolated Power Supply Feedback, Isolated RS-485 / RS-232 Communication, Medical Device Patient Isolation.
Isolated SPI / UART in Industrial Motor Drives
The SI8421AD-D-IS provides 2-channel unidirectional isolation between a low-voltage MCU control board and the high-voltage gate-driver section of a 480 Vac motor drive. Its 5 kVrms reinforced insulation and 7.5 mm wide-body SOIC creepage distance meet IEC 61800-5-1 reinforced-insulation requirements for industrial drives, while the 1 Mbps data rate supports isolated SPI up to 500 kHz and UART up to 1 Mbaud. The 20 kV/us CMTI rejects the high dv/dt transients generated by 10 kHz+ Si/SiC inverter switching. Compared to optocouplers, the Si8421 reduces propagation delay from 500 ns to under 35 ns and eliminates LED aging concerns.
Recomendado
Isolated Gate-Drive Signal Path for SiC/GaN Inverters
The SI8421AD-D-IS provides reinforced isolation between the gate-driver IC and the MCU in 600 V to 1200 V SiC and GaN solar/automotive inverters. Its 20 kV/us CMTI is sufficient for IGBT-based designs (typical dv/dt 5-15 kV/us), while engineers needing margin for next-gen SiC designs (typical dv/dt 25-50 kV/us) should choose the SI8421AB-D-IS variant with 35 kV/us CMTI. The 35 ns worst-case propagation delay preserves the tight timing budget between PWM update and gate-drive response, and the 2.7 V to 5.5 V supply range supports both 3.3 V MCU I/O and 5 V gate-driver logic directly.
Recomendado
Isolated Data Acquisition Front-End
The SI8421AD-D-IS isolates the digital control signals (SPI clock/data/select) between an MCU and a precision ADC or DAC front-end in high-voltage measurement equipment. Its 5 kVrms reinforced insulation protects the low-voltage controller from line-voltage transients on the sensor side, and its 1 Mbps data rate supports the SPI interface of most 16-bit and 18-bit precision converters. The default-LOW fail-safe behavior ensures the ADC enters a known-safe state if the isolated-side power is lost, preventing spurious measurements from reaching the controller. Compared to discrete optocouplers, the Si8421 saves 4-6 PCB components per channel.
Recomendado
Isolated Power Supply Feedback
The SI8421AD-D-IS replaces an optocoupler in the feedback path of an isolated DC-DC converter, carrying the feedback error signal from the secondary-side shunt reference to the primary-side PWM controller. Its 1 Mbps data rate is more than adequate for sub-MHz PWM feedback loops, and its 5 kVrms isolation matches the converter's primary-to-secondary insulation rating. The Si8421's 10x reliability improvement over optocouplers eliminates a known failure mode (LED CTR degradation) and reduces long-term drift in the feedback loop. Wide-body SOIC creepage (7.5 mm) satisfies IEC 62368-1 reinforced insulation for telecom and industrial power supplies.
Recomendado
Isolated RS-485 / RS-232 Communication
The SI8421AD-D-IS isolates the digital control signals of an RS-485 or RS-232 transceiver from the bus-side high-voltage transients in industrial fieldbus networks. Combined with a transceiver such as the TI ISO3082 or Maxim MAX3485, the Si8421 provides the 5 kVrms reinforced insulation required by IEC 61800-3 for industrial EMC compliance. The default-LOW fail-safe behavior keeps the bus in a recessive state if the controller loses power, preventing bus contention during fault conditions. Compared to integrated isolated transceivers, the Si8421 + discrete transceiver approach offers more flexibility in transceiver selection.
Recomendado
Medical Device Patient Isolation
The SI8421AD-D-IS in its wide-body 16-SOIC package provides 5 kVrms reinforced insulation meeting IEC 60601-1 patient-protection requirements for medical devices such as patient monitors, infusion pumps, and diagnostic imaging systems. The 7.5 mm creepage distance and 5 kVrms withstand support the Means of Patient Protection (MOPP) insulation required for patient-applied circuits. The device's CMOS technology eliminates the optocoupler LED aging concern that historically caused field returns in long-life medical equipment. Compared to discrete optocoupler solutions, the Si8421 reduces PCB area by ~60% and improves reliability by 10x per the manufacturer datasheet.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para SI8421AD-D-IS — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | SI8421AD-B-IS | SI8421AB-D-IS | SI8421AD-D-IS-R | ISO7221ADR | ISO7221MDR |
|---|---|---|---|---|---|---|
| Brand | Silicon Labs | Silicon Labs | Silicon Labs | Silicon Labs | Texas Instruments | Texas Instruments |
| Package | 16-SOIC wide-body | 16-SOIC wide-body (same) | 16-SOIC wide-body (same) | 16-SOIC wide-body (same) | 16-SOIC (verify pinout) | 16-SOIC wide-body (verify pinout) |
| Isolation Voltage (rms) | 5000 V | 5000 V | 5000 V | 5000 V | 2500 V (basic) | 5000 V |
| Channels / Direction | 2 / 2 forward | 2 / 2 forward | 2 / 2 forward | 2 / 2 forward | 2 / 2 forward | 2 / 2 forward |
| Data Rate (max) | 1 Mbps | 1 Mbps | 1 Mbps | 1 Mbps | 1 Mbps | 1 Mbps |
| Propagation Delay (max) | 35 ns | 35 ns | 35 ns | 35 ns | 42 ns | 42 ns |
| CMTI (min) | 20 kV/us | 35 kV/us | 35 kV/us | 20 kV/us | 25 kV/us | 25 kV/us |
| Fail-Safe Output | Default LOW | Default LOW | Default LOW | Default LOW | Default HIGH | Default HIGH |
| Unit Price (qty 1) | $3.20 | $3.30 (approx) | $3.40 (approx) | $3.20 (approx) | $2.80 (approx) | $3.60 (approx) |
Diferenciadores clave
- Highest CMTI in 16-SOIC wide-body Si8421 family at standard 20 kV/us rating (frente a SI8421AB-D-IS)
- Default-LOW fail-safe output matches industrial convention (frente a ISO7221ADR / ISO7221MDR)
- Reinforced insulation 5 kVrms in standard 16-SOIC wide-body footprint (frente a ISO7221ADR (basic isolation only))
Notas de diseño
Place 0.1 uF low-ESR ceramic bypass capacitors within 2 mm of each VDD pin (pins 3, 4, 11, 16 on this wide-body SOIC). Add a 1 uF to 10 uF bulk capacitor on each supply rail for high-transient-load conditions. The two VDD1 pins and two VDD2 pins are internally connected but should both be bypassed externally to minimize supply-induced channel-to-channel skew. Estimated: based on the Si8421 datasheet supply-current specification of ~1.8 mA per channel at 1 Mbps, total quiescent supply current is ~3.6 mA per side, well within the capability of a 0.1 uF bypass cap's ripple handling.
Maintain the 7.5 mm package creepage distance across the isolation barrier by keeping all PCB copper (traces, planes, vias) at least 7.5 mm apart between side-1 and side-2 nets. Do not place any traces, vias, or copper pours under the package body between side 1 and side 2, as this reduces effective creepage. For 5 kVrms reinforced insulation per IEC 60747-17, also maintain at least 0.5 mm clearance through-air above the PCB under the package. Wide-body SOIC is preferred over narrow-body SOIC for reinforced-insulation applications.
Route side-1 and side-2 grounds as separate nets (GND1 and GND2) with the isolation barrier physically between them; do not stitch them together anywhere on the PCB. Use a 4-layer PCB with side-1 ground on layer 2 and side-2 ground on layer 3, with the isolation barrier cutting through the entire stack-up. Keep input/output signal traces short (<25 mm) and far from the isolation barrier. Estimated: a 4-layer stack-up with 0.2 mm prepreg between layers provides typical inter-layer capacitance of ~1 pF/cm, which combines with the Si8421's internal RF architecture to maintain CMTI performance above the 20 kV/us minimum.
Do not connect side-1 ground to side-2 ground anywhere on the PCB - this defeats the isolation barrier and creates a ground loop. Do not assume default-HIGH fail-safe behavior on the D-option; this is the most common Si8421 option-code mistake. Do not route signal traces under the package body - this violates creepage distance. Do not exceed the maximum data rate of 1 Mbps - higher data-rate signals cause excessive pulse-width distortion on the lower-speed Si8421. For 10-150 Mbps signals, choose Si8441 or Si8461 family members instead.
The 1 Mbps data rate and 35 ns propagation delay are sufficient for SPI up to 500 kHz clock and UART up to 1 Mbaud. For longer PCB traces (>30 mcm), add a 10-50 ohm series termination resistor at the driver output to dampen ringing; the Si8421 outputs have ~5 ohm typical source impedance. If using the Si8421 for a 3.3 V to 5 V level shift (or vice versa), verify VDD1 and VDD2 supply voltages match the logic levels on each side of the isolation barrier; the Si8421 has independent supplies on each side and can perform level shifting for free, but only if both VDD rails are present and stable.
Información de cumplimiento
RoHS compliant per Skyworks/Silicon Labs product page. UL, CSA, and VDE safety certified per Si8421 family datasheet. AEC-Q100 not applicable - Si8421 is industrial-grade (-40 to +125 C), not automotive-grade qualified.
