Photometric Front Ends

The ADPD1080/ADPD1081 are highly efficient, photometric front ends, each with an integrated 14-bit analog-to-digital converter (ADC) and a 20-bit burst accumulator that works with flexible light emitting diode (LED) drivers. The ADPD1080/ADPD1081 stimulate an LED and measures the corresponding optical return signal. The data output and functional configuration occur over a 1.8 V I2C interface on the ADPD1080 or a serial port interface (SPI) on the ADPD1081. The control circuitry includes flexible LED signaling and synchronous detection.

The analog front end (AFE) features rejection of signal offset and corruption due to modulated interference commonly caused by ambient light without the need for optical filters or dc cancellation circuitry that requires external control.

Couple the ADPD1080/ADPD1081 with a low capacitance photodiode of <100 pF for optimal performance. The ADPD1080/ADPD1081 can be used with any LED. The ADPD1080 is available in a 16-ball, 2.46 mm × 1.4 mm WLCSP and a 28-lead, 4 mm × 4 mm LFCSP. The SPI only version, ADPD1081, is available in a 17-ball, 2.46 mm × 1.4 mm WLCSP.

Applications

* Wearable health and fitness monitors

* Clinical measurements, for example, SpO2

* Industrial monitoring

* Background light measurements

* Multifunction photometric front end

* Fully integrated AFE, ADC, LED drivers, and timing core

* Enables ambient light rejection capability without the need for photodiode optical filters

* Three 370 mA LED peak current drivers

* Flexible, multiple, short LED pulses per optical sample

* 20-bit burst accumulator enabling 20 bits per sample period