The ADS8684A and ADS8688A are 4- and 8-channel, integrated data acquisition systems based on a 16-bit successive approximation (SAR) analog-to-digital converter (ADC), operating at a throughput of 500 kSPS. The devices feature integrated analog front-end circuitry for each input channel with overvoltage protection up to ±20 V, a 4- or 8-channel multiplexer with automatic and manual scanning modes, and an on-chip, 4.096-V reference with low temperature drift. Operating on a single 5-V analog supply, each input channel on the devices can support true bipolar input ranges of ±10.24 V,
±5.12 V, ±2.56 V, ±1.28V and ±0.64V, as well as unipolar input ranges of 0 V to 10.24 V, 0 V to 5.12 V, 0 V to 2.56 V and 0 V to 1.28 V. The gain of the analog front-end for all input ranges is accurately trimmed to ensure a high dc precision. The input range selection is software-programmable and independent for each channel. The devices offer a
1-MΩ constant resistive input impedance irrespective of the selected input range.
The ADS8684A and ADS8688A offer a simple SPI-compatible serial interface to the digital host and also support daisy-chaining of multiple devices. The digital supply operates from 1.65 V to 5.25 V, enabling direct interface to a wide range of host controllers.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
ADS868xA | TSSOP (38) | 9.70 mm × 4.40 mm |
DATE | REVISION | NOTES |
---|---|---|
July 2014 | * | Initial release. |
PRODUCT | RESOLUTION (Bits) | CHANNELS | SAMPLE RATE (kSPS) |
---|---|---|---|
ADS8684A | 16 | 4, single-ended | 500 |
ADS8688A | 16 | 8, single-ended | 500 |
PIN | I/O | DESCRIPTION | ||
---|---|---|---|---|
NO. | NAME | |||
ADS8684A | ADS8688A | |||
1 | SDI | Digital input | Data input for serial communication. | |
2 | RST/PD | Digital input | Active low logic input. Dual functionality to reset or power-down the device. |
|
3 | DAISY | Digital input | Chain the data input during serial communication in daisy-chain mode. | |
4 | REFSEL | Digital input | Active low logic input to enable the internal reference. When low, the internal reference is enabled; REFIO becomes an output that includes the VREF voltage. When high, the internal reference is disabled; REFIO becomes an input to apply the external VREF voltage. |
|
5 | REFIO | Analog input, output | Internal reference output and external reference input pin. Decouple with REFGND on pin 6. | |
6 | REFGND | Power supply | Reference GND pin; short to the analog GND plane. Decouple with REFIO on pin 5 and REFCAP on pin 7. |
|
7 | REFCAP | Analog output | ADC reference decoupling capacitor pin. Decouple with REFGND on pin 6. | |
8 | AGND | Power supply | Analog ground pin. Decouple with AVDD on pin 9. | |
9 | AVDD | Power supply | Analog supply pin. Decouple with AGND on pin 8. | |
10 | AUX_IN | Analog input | Auxiliary input channel: positive input. Decouple with AUX_GND on pin 11. | |
11 | AUX_GND | Analog input | Auxiliary input channel: negative input. Decouple with AUX_IN on pin 10. | |
12 | NC | AIN_6P | Analog input | Analog input channel 6, positive input. Decouple with AIN_6GND on pin 13. No connection for the ADS8684A; this pin can be left floating or connected to AGND. |
13 | NC | AIN_6GND | Analog input | Analog input channel 6, negative input. Decouple with AIN_6P on pin 12. No connection for the ADS8684A; this pin can be left floating or connected to AGND. |
14 | NC | AIN_7P | Analog input | Analog input channel 7, positive input. Decouple with AIN_7GND on pin 15. No connection for the ADS8684A; this pin can be left floating or connected to AGND. |
15 | NC | AIN_7GND | Analog input | Analog input channel 7, negative input. Decouple with AIN_7P on pin 14. No connection for the ADS8684A; this pin can be left floating or connected to AGND. |
16 | AIN_0P | Analog input | Analog input channel 0, positive input. Decouple with AIN_0GND on pin 17. | |
17 | AIN_0GND | Analog input | Analog input channel 0, negative input. Decouple with AIN_0P on pin 16. | |
18 | AIN_1P | Analog input | Analog input channel 1, positive input. Decouple with AIN_1GND on pin 19. | |
19 | AIN_1GND | Analog input | Analog input channel 1, negative input. Decouple with AIN_1P on pin 18. | |
20 | AIN2_GND | Analog input | Analog input channel 2, negative input. Decouple with AIN_2P on pin 21. | |
21 | AIN_2P | Analog input | Analog input channel 2, positive input. Decouple with AIN_2GND on pin 20. | |
22 | AIN_3GND | Analog input | Analog input channel 3, negative input. Decouple with AIN_3P on pin 23. | |
23 | AIN_3P | Analog input | Analog input channel 3, positive input. Decouple with AIN_3GND on pin 22. | |
24 | NC | AIN_4GND | Analog input | Analog input channel 4, negative input. Decouple with AIN_4P on pin 25. No connection for the ADS8684A; this pin can be left floating or connected to AGND. |
25 | NC | AIN_4P | Analog input | Analog input channel 4, positive input. Decouple with AIN_4GND on pin 24. No connection for the ADS8684A; this pin can be left floating or connected to AGND. |
26 | NC | AIN_5GND | Analog input | Analog input channel 5, negative input. Decouple with AIN_5P on pin 27. No connection for the ADS8684A; this pin can be left floating or connected to AGND. |
27 | NC | AIN_5P | Analog input | Analog input channel 5, positive input. Decouple with AIN_5GND on pin 26. No connection for the ADS8684A; this pin can be left floating or connected to AGND. |
28 | AGND | Power supply | Analog ground pin | |
29 | AGND | Power supply | Analog ground pin | |
30 | AVDD | Power supply | Analog supply pin. Decouple with AGND on pin 31. | |
31 | AGND | Power supply | Analog ground pin. Decouple with AVDD on pin 30. | |
32 | AGND | Power supply | Analog ground pin | |
33 | DGND | Power supply | Digital ground pin. Decouple with DVDD on pin 34. | |
34 | DVDD | Power supply | Digital supply pin. Decouple with DGND on pin 33. | |
35 | ALARM | Digital output | Active high alarm output | |
36 | SDO | Digital output | Data output for serial communication | |
37 | SCLK | Digital input | Clock input for serial communication | |
38 | CS | Digital input | Active low logic input; chip-select signal |