READ_SAMPLE_BUF is a manufacturer-specific command used to read the latest sixty-four (64) samples of a particular parameter from a round-robin ADC buffer available in the device RAM. This allows multiple ADC samples to be captured at a higher speed and read out at on go without the bottleneck of reading individual samples sequentially over the PMBus® serial interface. This allows the system designer to reconstruct the time domain profile/waveform of that parameter in a given time interval. This could be useful during design or system debugging by functioning like an in-built "digital oscilloscope". The rate at which ADC samples are updated in the buffer depends on the effective ADC sampling period and the decimation rate/sample skip count. If Bit[3] of the DEVICE_CONFIG register is set to high, the effective ADC sampling period is 18 µs (typical). Otherwise, it will be 11 µs (typical) by default. The ADC channel to sample for buffering and the decimation rate/sample skip count can be configured through the ADC_CONFIG_2 register. By selecting different decimation rates, users can choose between “fine time resolution with short aperture” and “coarse time resolution with wide aperture”.

This command uses the PMBus® block read protocol with a block size of sixty-four (64).

Follow the PMBus® DIRECT format conversion using the coefficients in Table 8-67 and Equation 19, to convert the hexadecimal data bytes into their real-world values in the appropriate unit.

The ADC sample buffer starts buffering as soon as the device powers up. The buffering is paused under two different conditions:

1. The instant READ_SAMPLE_BUF command is issued. This ensures the sample buffer is not overwritten with new values while the host is reading out the previous set of values. After sixty-four (64) bytes have been read, it will again start buffering new samples.

2. In the event of a fault, which is latched internally as shown in Table 8-2. This ensures the snapshot of the samples prior to the fault event is preserved even if there's a delay from host in reading out the sample buffer. After issuing the CLEAR_FAULTS command, or writing OPERATION OFF command followed by OPERATION ON command, or toggling the EN/UVLO pin, it will again start buffering new samples.

Figure 8-20 ADC Sample Buffering Example