Datasheet Si8921/22 (Silicon Labs) - 4
| Manufacturer | Silicon Labs |
| Description | Isolated Amplifier for Current Shunt Measurement |
| Pages / Page | 30 / 4 — 2. System Overview. Si8921. Transmitter. Receiver. Figure 2.1. Si8921 … |
| Revision | 0.5 |
| File Format / Size | PDF / 548 Kb |
| Document Language | English |
2. System Overview. Si8921. Transmitter. Receiver. Figure 2.1. Si8921 Functional Block Diagram. Si8922
Model Line for this Datasheet
Text Version of Document
Si8921/22 Data Sheet System Overview
2. System Overview
The input to the Si8921/22 is designed for low-voltage, differential signals. This is ideal for connection to low resistance current shunt measurement resistors. The Si8921A/22A has a specified full scale input range of ±62.5 mV, and the Si8921B/22B has a specified full scale input range of ±250 mV. In both cases, the internal gain is set so that the full scale output is 2.05 V. The Si8921 provides a differ- ential output voltage while the Si8922 provides a single-ended output voltage. The Si8921/22 modulates the analog signal in a unique way for transmission across the semiconductor based isolation barrier. The input signal is first converted to a pulse-width modulated digital signal. On the other side of the isolation barrier, the signal is demodula- ted. The resulting PWM signal is then used to faithfully reproduce the analog signal. This solution provides exceptional signal bandwidth and accuracy. The Si8921/22 implements a fail-safe output when the high-side supply voltage VDDA goes away. The fail-safe output is nominally 2.8 V, which can be differentiated from the maximum clipping output voltage of 2.6 V to simplify diagnostics on the system level. The Si8921 outputs a negative differential output voltage while the single-ended Si8922 outputs a positive voltage. When a loss of VDDA supply occurs, the part will automatically move into a lower power mode that reduces IDDB current to approxi- mately 1 mA. Similarly, a loss of VDDB supply will reduce IDDA current to approximately 1 mA. When the supply voltage is returned, normal operation begins in approximately 250 μs.
Si8921
VDDA VDDB OSC AIP AOP PWM PWM AIN AON
Transmitter Receiver
GNDA CMOS Isolation GNDB
Figure 2.1. Si8921 Functional Block Diagram Si8922
VDDA VDDB OSC AIP AO PWM PWM AIN NC
Transmitter Receiver
GNDA CMOS Isolation GNDB
Figure 2.2. Si8922 Functional Block Diagram silabs.com
| Building a more connected world. Preliminary Rev. 0.5 | 4 Document Outline 1. Ordering Guide 2. System Overview 3. Current Sense Application 4. Electrical Specifications 4.1 Regulatory Information 4.2 Typical Operating Characteristics 5. Pin Descriptions 5.1 Si8921 Pin Descriptions 5.2 Si8922 Pin Descriptions 6. Packaging 6.1 Package Outline: 8-Pin Wide Body Stretched SOIC 6.2 Package Outline: 8-Pin Narrow Body SOIC 6.3 Land Pattern: 8-Pin Wide Body Stretched SOIC 6.4 Land Pattern: 8-Pin Narrow Body SOIC 6.5 Top Marking: 8-Pin Wide Body Stretched SOIC 6.6 Top Marking: 8-Pin Narrow Body SOIC 7. Revision History
2. System Overview
The input to the Si8921/22 is designed for low-voltage, differential signals. This is ideal for connection to low resistance current shunt measurement resistors. The Si8921A/22A has a specified full scale input range of ±62.5 mV, and the Si8921B/22B has a specified full scale input range of ±250 mV. In both cases, the internal gain is set so that the full scale output is 2.05 V. The Si8921 provides a differ- ential output voltage while the Si8922 provides a single-ended output voltage. The Si8921/22 modulates the analog signal in a unique way for transmission across the semiconductor based isolation barrier. The input signal is first converted to a pulse-width modulated digital signal. On the other side of the isolation barrier, the signal is demodula- ted. The resulting PWM signal is then used to faithfully reproduce the analog signal. This solution provides exceptional signal bandwidth and accuracy. The Si8921/22 implements a fail-safe output when the high-side supply voltage VDDA goes away. The fail-safe output is nominally 2.8 V, which can be differentiated from the maximum clipping output voltage of 2.6 V to simplify diagnostics on the system level. The Si8921 outputs a negative differential output voltage while the single-ended Si8922 outputs a positive voltage. When a loss of VDDA supply occurs, the part will automatically move into a lower power mode that reduces IDDB current to approxi- mately 1 mA. Similarly, a loss of VDDB supply will reduce IDDA current to approximately 1 mA. When the supply voltage is returned, normal operation begins in approximately 250 μs.
Si8921
VDDA VDDB OSC AIP AOP PWM PWM AIN AON
Transmitter Receiver
GNDA CMOS Isolation GNDB
Figure 2.1. Si8921 Functional Block Diagram Si8922
VDDA VDDB OSC AIP AO PWM PWM AIN NC
Transmitter Receiver
GNDA CMOS Isolation GNDB
Figure 2.2. Si8922 Functional Block Diagram silabs.com
| Building a more connected world. Preliminary Rev. 0.5 | 4 Document Outline 1. Ordering Guide 2. System Overview 3. Current Sense Application 4. Electrical Specifications 4.1 Regulatory Information 4.2 Typical Operating Characteristics 5. Pin Descriptions 5.1 Si8921 Pin Descriptions 5.2 Si8922 Pin Descriptions 6. Packaging 6.1 Package Outline: 8-Pin Wide Body Stretched SOIC 6.2 Package Outline: 8-Pin Narrow Body SOIC 6.3 Land Pattern: 8-Pin Wide Body Stretched SOIC 6.4 Land Pattern: 8-Pin Narrow Body SOIC 6.5 Top Marking: 8-Pin Wide Body Stretched SOIC 6.6 Top Marking: 8-Pin Narrow Body SOIC 7. Revision History
