SR087 is an inductorless switching regulator designed to operate directly from a rectified AC line. The operating principle is to turn on a pass transistor when the rectified AC is below the output voltage, and to turn it off when the output voltage reaches a specific level. A linear regulator supplied by VOUT provides an additional fixed 5.0V output. Efficiencies of around 55% may be realized for loads up to 1.0W in 120VAC applications, with around 50% efficiencies for loads up to 800mW in 230VAC applications. A logic-level enable input allows the SR087 to be disabled – useful when it is employed as a keep-alive power supply. WARNING! Galvanic isolation is not provided. Dangerous voltages are present when connected to the AC line. It is the responsibility of the designer employing the SR087 to ensure adequate safeguards are in place to protect the end user from electrical shock. The circuits shown in this datasheet are not guaranteed to meet surge and conducted EMI requirements. The effectiveness of these circuits may vary with a particular application. The designer should conduct tests to ascertain compliance with applicable standards and regulations.
Additional Features
Efficient operation without magnetics
No high voltage capacitors
Adjustable main output voltage (9.0 to 50V)
Additional 5.0V internal regulator
Up to 100mA combined output current
Single BOM for 120VAC/230VAC
Built-in soft start
Less than 200mW standby power
SR087 is an inductorless switching regulator designed to operate directly from a rectified AC line. The operating principle is to turn on a pass transistor when the rectified AC is below the output voltage, and to turn it off when the output voltage reaches a specific level. A linear regulator supplied by VOUT provides an additional fixed 5.0V output. Efficiencies of around 55% may be realized for loads up to 1.0W in 120VAC applications, with around 50% efficiencies for loads up to 800mW in 230VAC applications. A logic-level enable input allows the SR087 to be disabled – useful when it is employed as a keep-alive power supply. WARNING! Galvanic isolation is not provided. Dangerous voltages are present when connected to the AC line. It is the responsibility of the designer employing the SR087 to ensure adequate safeguards are in place to protect the end user from electrical shock. The circuits shown in this datasheet are not guaranteed to meet surge and conducted EMI requirements. The effectiveness of these circuits may vary with a particular application. The designer should conduct tests to ascertain compliance with applicable standards and regulations.
Additional Features
- Efficient operation without magnetics
- No high voltage capacitors
- Adjustable main output voltage (9.0 to 50V)
- Additional 5.0V internal regulator
- Up to 100mA combined output current
- Single BOM for 120VAC/230VAC
- Built-in soft start
- Less than 200mW standby power
