ISOS510-SP is commonly used in the feedback control loops of isolated power supplies. This device is used to solve the problem of feeding back current while isolating the primary and secondary domains to regulate the output voltage.

In power supplies, the output voltage is isolated from main input voltage using a transformer (for example: flyback converter). For analog power supply units, the controller IC is typically on the primary side of the transformer. For closed loop control, measuring the output voltage on the secondary side and feeding the voltage back to the controller on the primary is necessary. The most common method of achieving this design is using an isolator such as ISOS510-SP, error amplifier (commonly TL1431SP), and a voltage comparator to form a feedback loop across the isolation barrier

Figure 8-1 illustrates a typical isolated power supply. In this implementation, the output voltage is sensed by an error amplifier using the resistor divider (R1 and R2). Depending on the voltage level that the error amplifier senses, the TL1431SP can drive the current of the ISOS510-SP higher or lower which is then compared to a voltage reference. The information is passed across the isolation barrier through ISOS510-SP to the primary side, where the PWM control circuit modulates the power stage to regulate the output voltage. The TL1431SP and ISOS510-SP play an important role for stable feedback and control loop.

The ISOS510-SP devices enable improvements in transient response, reliability, and stability as compared to commonly used optocoupler as the CTR is stable over wide temperature range providing a small, low-cost, highly reliable, and easy-to-design implementation.