SLYT841 july   2023 ADS1261

 

  1.   1
  2. 1Introduction
  3. 2Power-supply specifications
  4. 3Transient currents
  5. 4Power-supply circuit options
  6. 5Low-power systems: Power down or power off?
  7. 6Related Website

2 Power-supply specifications

Current consumption in an ADC data sheet is an average value specified at steady-state operating conditions. An ADC with many different operating conditions requires the specification of several current values. These conditions can include an average ADC supply current that scales relative to the data rate or increased current demand when enabling internal features such as programmable gain amplifiers (PGAs) or voltage references (VREFs). As an example, Table 1 shows the data-sheet power-supply specifications at different operating conditions for TI’s ADS1261, a 24-bit, 40-kSPS, 11-channel delta-sigma ADC with an integrated PGA and VREF.

Table 1 The data-sheet power-supply specifications for the ADS1261.
Power Supply
Parameter Test Conditions MIN TYP MAX Unit
IAVVD, IAVSS Analog supply current PGA Bypass 2.7 4.5 mA
PGA mode, gain = 1 to 32 3.8 6
PGA mode, gain = 64 or 128 4.3 6.5
Power-down mode 2 8 µA
IAVVD, IAVSS Analog supply current (by function) Voltage reference 0.2 mA
40-kSPS mode 0.5
Current sources As programmed
IDVDD Digital supply current 20 SPS 0.4 0.65 mA
40 kSPS 0.6 0.85
Power-down mode 30 50 µA
PD Power dissipation PGA mode 20 32 mW
Power-down mode 0.1 0.2

The highlighted PGA Bypass section in Table 1 shows that the average analog current drawn by the ADS1261 during normal operation with the PGA bypassed is 2.7 mA (typical) or 4.5 mA (maximum). The highlighted “by function” section indicates how much the current increases when enabling each function. All of these supply-current specifications are characterized by measuring the average current drawn by the device after the current settles.

Data-sheet power-supply specifications therefore average out any transient current demand that the device or supporting circuitry requires during normal operation. This is important because transient currents during startup and switching can be significantly larger than the values specified in the data sheet. A reliable system design must be able to account for both average and transient current demand.