That part is old. We recommend ADPD1080 or ADPD4100. ADPD1080 is our cost efficient solution and ADPD4100 is our higher end, high SNR, power efficient solution. Also, if you require 90+ dB DC SNR, you have to use ADPD4100.
May I ask why you’re using such long LED pulses? Ideally, you should not use the settings you’re currently using. For the best PPG performance, please stick to the recommendations on Page 26 of the datasheet and the Table 18 on that page. Using longer LED pulses makes the system prone to ambient light issue, the main aspect of this IC is to use shorter pulses to suppress/reject ambient light. Also, you need to check whether you set all the other settings right. Especially TIA BIAS voltage and cathode voltage could be critical in reducing noise. It could be a linear dynamic range issue here as well. You need to check whether you are in safe, linear region. When you reduce the LED currents, what do you see?