16-bit 1MHz synchronous sampling ADC chip ADS8329

ADS8329 is a low-power, 16-bit, 1MSPS analog-to-digital converter (ADC) with unipolar input and sample-and-hold function.
Considering cost and performance, the price-performance ratio is average.
 

Notes:
1. The maximum sampling rate of this ADC is 1M, and the SPI serial output is 16-bit, so the SPI rate will be very high. The SPI_CLK this time is 21M, and it is difficult to collect 1M signals.
2. When sampling multiple chips simultaneously, you must pay attention to the speed of SPI, or use one pin to control the sample and hold, and read data from multiple SPIs separately.
3. CS chip select, each time you read and write data, you must pull it low and then pull it high. Sending multiple instructions after pulling it low at one time will result in no response.
4. The SPI configuration register is very simple, and single-chip acquisition almost does not need to be configured. Pay attention to the timing of the control signal to complete it.
5. In terms of hardware, pay attention to the SPI line as short and equal as possible, and connect a small capacitor of pf level in parallel at the receiving end to reduce the electromagnetic interference caused by signal overshoot. (Optimization direction)
6. Pay attention to the power supply requirements of the ADS8329 chip, ①+VA = 4.5 V to 5.5 V, +VBD = 1.65 V to 5.5 V, VREF = 5 V, and fSAMPLE = 1 MHz, or ②+VBD = 1.65 V to 1.5×(+VA), VREF = 2.5 V, fSAMPLE = 1 MHz for 3 V ≤ +VA ≤ 3.6 V. The project uses the ② scheme for power supply. Also pay attention to the analog input range of 0~VREF.
 
The hardware circuit
design is relatively simple, the instrument is differential, amplified by 2 times, pay attention to the signal range of 0-2.5V, and do not connect to negative voltage. The voltage reference is REF3025, and the LDO voltage regulator chip is the low-noise and high-PSRR LP5907MFX.
 
The keil program
uses TIM3 as the trigger for synchronous sampling. In the MX_TIM3_Init configuration, the count value of 84 is a 1us sampling period, and the count value of 168 is a 2us sampling period. In ADS8329_Init, the clock is turned on and
SPI3 is used to read and write the ADC register. It is configured in MX_SPI3_Init. In ADS8329_Init, SPI is turned on and the ADC is configured.
In the timer interrupt, the pin timing control is performed, TIM3_IRQHandler function. When changing the main frequency or master control, it is recommended to use an oscilloscope or logic analyzer to check the timing.
 
The program has added many comments. If you don’t understand, you are welcome to communicate with me. The
 
measured results
input uses a resistor divider of 1/2 and amplifies it by 2 times, so the measured results are consistent with the oscilloscope.
 
The following figure shows two ADC chips cascaded, with a sampling rate of 500k and a 50k signal.
 
The following figure is a test photo of a single chip