Product Overview
This document provides a detailed example calculation for determining the appropriate load resistance (RL) for the RPI-221, a component likely used in photointerrupter applications. The calculation considers customer circuit parameters, forward current (IF), minimum collector current (IC), and the impact of aging on infrared LED light emitting capacity. The objective is to ensure the load resistor satisfies specific threshold voltage requirements (VHi and VLo) within the customer's circuit, thereby defining a suitable operating range for the load resistance.
Product Attributes
- Product Model: RPI-221 (example used for calculation)
Technical Specifications
| Parameter | Value | Notes |
|---|---|---|
| Customer Circuit VCC | 5V | |
| Customer Circuit IF | 20.6mA | |
| ROHM SPEC IC Min (for IF=20mA) | 0.2mA | |
| Calculated IC Min (for IF=20.6mA) | 0.21mA | |
| Aging Factor (Light Emission Decrease over 10 years) | 50% (0.5) | |
| Adjusted IC Min (considering aging) | 0.105mA | |
| Infrared Emitting Diode VF | 1.3V | |
| Customer Circuit VHi Threshold | 3.8V or higher | Estimation value |
| Customer Circuit VLo Threshold | 1.0V or lower | Estimation value |
| Maximum Dark Current (Iceo max) | 10A | Assumed value |
| Calculated RL Min | > 36k | Derived from VHi threshold |
| Calculated RL Max | < 100k | Derived from VLo threshold and Iceo max |
| Resulting Load Resistance Range | 36k < RL < 100k | |
| Infrared LED Service Life (rated input current) | 100,000 hours | Assumes life completes at 50% light emitting capacity |
2404071830_ROHM-RPI-1133_C3656419.pdf
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