SI8921BD-IS4 - ±250 mV Isolated Amplifier, 5 kV | Skyworks
Référence : SI8921BD-IS4 ✓ Actif| Qté | Prix unitaire | Total |
|---|---|---|
| 1 | $1.39 | $1,39 |
| 10 | $1.3 | $13,00 |
| 100 | $1.12 | $112,00 |
| 500 | $0.98 | $490,00 |
| 1 000 | $0.85 | $850,00 |
| 3 000 | $0.72 | $2 160,00 |
SI8921BD-IS4 Présentation
An isolated amplifier is a type of analog amplifier that combines a precision front-end differential amplifier with a galvanic isolation barrier, transferring the signal across the barrier through capacitive or transformer coupling. The isolation barrier protects low-voltage control circuitry from high-voltage common-mode transients on the field side, enabling safe measurement of floating signals such as those present across current-shunt resistors in motor drives, solar inverters, and uninterruptible power supplies. Within the broader hierarchy, an isolated amplifier belongs to the isolation IC family, which includes digital isolators and isolated gate drivers - all of which form essential building blocks in power-management and industrial-automation systems requiring reinforced insulation per IEC 60747-17 and UL 1577.
The SI8921BD-IS4 features a specified input range of ±250 mV, well suited for direct connection across low-ohm shunt resistors in high-current paths. Its differential output swings to a 2.5 V peak full-scale signal, which can be fed directly into the ADC front-end of a motor controller or power-conversion MCU. The device's low offset and drift specifications eliminate the need for periodic calibration in many systems, while its 0.8 µs propagation delay supports closed-loop current control in fast-switching converters.
Architecturally, the SI8921BD-IS4 integrates a precision chopper-stabilized input amplifier, a sigma-delta modulator, an isolation capacitor barrier, and a differential output decoder on the low-voltage side. The internal LDO regulators on both sides of the barrier simplify power-supply design - the high-side is powered from a 3.0 V to 5.5 V supply, and the low-side is powered independently from 3.0 V to 5.5 V. The CMOS output stage is capable of driving 2 kΩ loads with low distortion.
Typical applications include current-shunt monitoring in three-phase motor drives, photovoltaic inverter string-current sensing, UPS battery-current measurement, industrial process-control isolation, and high-voltage rail monitoring in telecom rectifiers. The differential output interfaces directly with SAR ADCs and sigma-delta converters found in C2000 and PIC32 families.
When designing with this device, place bypass capacitors of 0.1 µF and 1 µF close to both VDDA and VDDD pins, keep the input traces short and balanced to preserve CMRR, and observe the creepage and clearance rules of the wide-body SOIC-8 footprint to maintain the 5 kV isolation rating. The differential output should be routed as a matched pair to avoid common-mode pickup in noisy switching environments.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found on a single manufacturer product page or distributor listing.
Alternatives de remplacement direct pour SI8921BD-IS4 — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Outil de comparaison rapide — sélectionnez des références alternatives pour une comparaison côte à côte :
SI8921AD-IS4
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
SI8921BD-AS4
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
SI8921AD-AS4
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
SI8921BD-IS4 Valeurs maximales et caractéristiques électriques
| Product Type | Isolated Analog Amplifier |
| Specified Input Range | ±250 mV (differential) |
| Isolation Rating | 5.0 kV RMS |
| Signal Delay (Propagation) | 0.8 µs (typical) |
| Input Offset Voltage | ±0.40 µV (typical) |
| Gain Error | ±0.06% (typical) |
| Offset Drift | 0.5 µV/°C |
| Gain Drift | -9 ppm/°C (typical) |
| Type de sortie | Differential analog, 2.5 V peak full-scale |
| High-Side Supply Voltage | 3.0 V to 5.5 V |
| Low-Side Supply Voltage | 3.0 V to 5.5 V |
| Boîtier | Wide-body stretched SOIC-8 |
| Type de montage | Surface Mount |
| Température de fonctionnement | -40°C to +125°C |
| Niveau MSL | 2A (4 weeks) |
| Statut RoHS | ROHS3 Compliant |
| REACH Status | REACH Unaffected |
Configuration des broches de SI8921BD-IS4
| Broche 1 | VDDD — Low-side supply voltage (3.0 V to 5.5 V) |
| Broche 2 | GNDD — Low-side ground |
| Broche 3 | OUTP — Positive differential analog output |
| Broche 4 | OUTN — Negative differential analog output |
| Broche 5 | GNDA — High-side ground (shunt negative terminal) |
| Broche 6 | INP — Positive differential analog input |
| Broche 7 | INN — Negative differential analog input |
| Broche 8 | VDDA — High-side supply voltage (3.0 V to 5.5 V) |
Applications typiques
SI8921BD-IS4 convient pour 6 applications: Three-Phase Motor Drive Current Sensing, Photovoltaic Inverter String-Current Monitoring, UPS Battery Current Measurement, Industrial Process-Control Isolation, Telecom Rectifier High-Voltage Rail Monitoring, Solar Charge Controller Battery Monitoring.
Three-Phase Motor Drive Current Sensing
The SI8921BD-IS4 is ideal for three-phase motor-drive current sensing in industrial servo drives, EV traction inverters, and HVAC compressors. Its ±250 mV differential input range matches a 2 mΩ shunt at ±125 A peak phase current, well within the typical IGBT phase-current envelope of variable-frequency drives. The 0.8 µs propagation delay, documented in the Skyworks Si8921/22 datasheet, supports field-oriented control (FOC) loops running at 20 kHz PWM where the current feedback must settle within one switching cycle. The 5 kV RMS isolation safely bridges the 480-600 VAC bus to the low-voltage MCU ADC, eliminating the need for discrete isolated op-amp + isolated power-supply designs.
Recommandé
Photovoltaic Inverter String-Current Monitoring
The SI8921BD-IS4 enables accurate per-string current monitoring in photovoltaic inverters and DC optimizers where the high-side of the shunt floats at up to 1500 V DC. According to the Skyworks datasheet, the 5 kV RMS isolation rating provides the reinforced insulation required by IEC 62109 for PV converter safety. The differential output drives directly into the SAR ADC inputs of a PIC32MZ or C2000 microcontroller, while the chopper-stabilized input stage keeps offset error below 1 µV across the operating temperature range, eliminating periodic field recalibration in rooftop and utility-scale solar installations.
Recommandé
UPS Battery Current Measurement
The SI8921BD-IS4 provides isolated battery-current measurement in on-line and line-interactive UPS systems where the battery stack may operate at 48 V, 192 V, or 384 V DC and the controller sits on the AC-mains side. The differential ±250 mV input range matches a 5 mΩ shunt at ±50 A battery charge/discharge current, while the 5 kV isolation barrier protects the low-voltage monitoring MCU from DC-bus transients during battery-switchover events. The 0.8 µs signal delay, per the Skyworks datasheet, supports State-of-Charge (SoC) algorithms that require sub-millisecond current-loop feedback for accurate coulomb counting in lithium-ion battery banks.
Recommandé
Industrial Process-Control Isolation
The SI8921BD-IS4 is widely deployed in industrial process-control systems to bridge 4-20 mA current-loop transmitters and shunt-based flow meters to PLC analog inputs. The wide-body SOIC-8 package provides the creepage and clearance distances required by IEC 61010-1 for measurement-category II installations. According to the Skyworks datasheet, the ±0.06% typical gain error and ±0.40 µV offset are well below the 0.1% accuracy requirement of most process transmitters, while the differential output rejects common-mode noise from VFD-driven actuators on the factory floor.
Recommandé
Telecom Rectifier High-Voltage Rail Monitoring
The SI8921BD-IS4 enables isolated DC-rail voltage monitoring in -48 V telecom rectifiers and 380 V DC distribution systems. Its ±250 mV input range accommodates a 25 mΩ bus-bar shunt at ±10 A nominal load, while the 5 kV RMS isolation exceeds the 1500 V working-voltage requirement of GR-1089 telecom standards. The Skyworks datasheet specifies -40°C to +125°C industrial temperature operation, suitable for outdoor telecom cabinet environments where ambient temperatures swing from -25°C in winter to +70°C in summer.
Recommandé
Solar Charge Controller Battery Monitoring
The SI8921BD-IS4 provides isolated battery-current sensing in MPPT solar charge controllers and off-grid hybrid inverter systems. Its ±250 mV differential input directly connects to the high-side shunt in the charge path, while the 5 kV isolation barrier protects the low-voltage MPPT controller from battery-stack voltages up to 192 V DC. The 0.8 µs propagation delay supports high-frequency MPPT algorithms running at 50-100 kHz switching frequency, and the differential output drives directly into the SAR ADC of a PIC18 or PIC24 microcontroller for high-resolution State-of-Charge estimation.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour SI8921BD-IS4 — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | SI8921AD-IS4 | SI8921BD-AS4 | SI8921AD-AS4 |
|---|---|---|---|---|
| Brand | Skyworks | Skyworks | Skyworks | Skyworks |
| Package | Wide-body stretched SOIC-8 | Wide-body stretched SOIC-8 - same | Wide-body stretched SOIC-8 - same | Wide-body stretched SOIC-8 - same |
| Specified Input Range | ±250 mV | ±62.5 mV (-75%) | ±250 mV (identical) | ±62.5 mV (-75%) |
| Isolation Rating | 5.0 kV RMS | 5.0 kV RMS (identical) | 5.0 kV RMS (identical) | 5.0 kV RMS (identical) |
| Automotive Grade (AEC-Q100) | No (commercial grade) | No (commercial grade) | Yes (AEC-Q100 qualified) | Yes (AEC-Q100 qualified) |
| Signal Propagation Delay | 0.8 µs | 0.8 µs (identical) | 0.8 µs (identical) | 0.8 µs (identical) |
| Output Type | Differential (2.5 V peak full-scale) | Differential (identical) | Differential (identical) | Differential (identical) |
| Operating Temperature Range | -40°C to +125°C | -40°C to +125°C (identical) | -40°C to +125°C (identical) | -40°C to +125°C (identical) |
Principaux différenciateurs
- Higher input range for high-current shunt sensing (vs SI8921AD-IS4)
- Commercial-grade pricing vs. automotive premium (vs SI8921BD-AS4)
- Origin and support - Skyworks Solutions (vs SI8921BD-AS4 (same brand, different suffix))
Notes de conception
Place 0.1 µF and 1 µF X7R bypass capacitors as close as possible to both VDDA (pin 8) and VDDD (pin 1) with the ground returns going directly to the GNDA (pin 5) and GNDD (pin 2) pins respectively. Keep the input traces INP (pin 6) and INN (pin 7) short, balanced, and routed over a continuous ground plane to preserve the common-mode rejection ratio. Maintain at least 8 mm creepage between the high-side and low-side copper pours on the top and bottom layers to preserve the 5 kV isolation rating per IEC 60747-17.
Do not connect the high-side ground (GNDA) and low-side ground (GNDD) together - these grounds must remain isolated to maintain the galvanic isolation barrier. Do not route any signal between the high-side and low-side copper pours on inner PCB layers; signals crossing the isolation barrier must use the internal capacitive isolation channels of the Si8921. Forgetting this and shorting GNDA to GNDD will destroy the isolation rating and may damage downstream control circuitry during high-voltage transients.
Route the OUTP (pin 3) and OUTN (pin 4) differential output traces as a matched-length pair with at least 3W spacing from any digital signals or switching-node traces. The differential output should be terminated with a 100 Ω differential resistor at the ADC input if the trace length exceeds 50 mm. The differential output swing of 2.5 V peak full-scale must be scaled to the ADC input range through a resistive divider or attenuator if the ADC operates from 3.3 V and accepts only 0-Vcc inputs.
The wide-body SOIC-8 package has a typical thermal resistance θJA of approximately 80 °C/W. Estimated: at maximum ambient temperature of 85°C and full 5 V supply on both sides, total power dissipation is around 50 mW, yielding a junction-temperature rise of only 4°C - thermal management is not a concern. However, in high-density designs with adjacent heat-generating power MOSFETs, leave at least 3 mm of clearance around the SI8921BD-IS4 to prevent PCB temperature gradients from inducing measurement error.
Informations de conformité
RoHS3 compliant and REACH unaffected per Skyworks product data (originally Silicon Labs data, unchanged by acquisition). Not AEC-Q100 qualified in the IS4 commercial-grade variant - choose AS4 suffix for AEC-Q100 automotive grade. Halogen-free and conflict-minerals status not stated in verified data - set to unknown.
