Other Parts Discussed in Thread: ADS1115, , ADS1015
I have an application that requires measurement of eight single-ended channels preferably at a sample rate of 100 SPS. I have used the ADS1115 in other ADC sampling applications, so I put together a board with two VSSOP-10 ADS1115s.
When I started prototyping I realized that one of the ADS1115s ("B" marked 0B BOGI // ADS1115IDGSR) is much slower than the other one ("A" marked 07 TI 19J6 / ADS1115BQDGSRQ1). The A-chip (Q1) will return single mode conversions in less than one millisecond, while the "B" chip requires 8-9ms between single mode conversions. If I run in continuous mode, but switch between channels at every read, I see the same proportion of latency between the two different chips.
I have scoured the data sheets for both, but I do not see anything in the Q1 data sheet that indicates why it is so much faster. My application will work and I can just barely squeeze out 100 SPS using the Q1's, but not the IDGSR chips. On my bench I've got 3 Q1s and 4 of the others and they all behave the same, so I assume this isn't some type of anomaly. I'm testing them both with the same 400K I2C bus, sampling set to 860 SPS, and a PGA of 6.144.
Can you confirm that the Q1 chips, by design, are almost 10X faster in their conversion processing?