The SM3320A is an image sensor IC that incorporates a single-element photodiode and optical detection circuit in an ultra small package. In the field of authentication of currency and securities, the demand for authentication using wavelengths from UV to infrared for improved security performance has been growing. However, in existing optical detector circuits, a general-use photodiode and op amp are required for different wavelengths, which places limits on the design and degree of freedom of wavelength detection.
The SM3320A uses a 1mm2 photodiode and charge storage amplifier, its rate of response can be controlled using a serial interface, it can detect wavelengths ranging from UV to infrared with high rate of response, and it can also compensate for variations in LED intensity. It also features a dark current compensation circuit, enabling it to generate a stable output signal within the operating temperature range. In addition, several SM3320A devices can be connected in parallel to increase the width of detection, allowing it to support a wide range of optical detection systems.