AD7654ASTZ vs AD7655ASTZ

The AD7655ASTZ is a 16-bit, 1 MSPS, dual-channel simultaneous-sampling successive-approximation (SAR) ADC with two on-chip track-and-hold amplifiers and a flexible parallel/serial interface. The AD7654ASTZ is a 16-bit, 500 kSPS, dual-channel SAR ADC that also supports simultaneous sampling of two inputs but operates at half the throughput rate of the AD7655. Both are pin-compatible members of Analog Devices' PulSAR family in 48-lead LQFP packages, but the AD7655 provides higher speed while the AD7654 targets lower-power, lower-rate applications.

Yes. Both devices are offered in the same 48-lead LQFP (STZ suffix) package with the same pinout, which allows a common PCB footprint. However, pin compatibility does not guarantee functional equivalence; the maximum sampling rate, power consumption, and some timing parameters differ, so firmware and clocking must be validated against the respective datasheets before substitution.

The AD7655ASTZ supports a maximum throughput of 1 MSPS per channel, while the AD7654ASTZ supports a maximum throughput of 500 kSPS per channel. Designs requiring the higher rate must use the AD7655ASTZ; the AD7654ASTZ is suitable only where 500 kSPS is sufficient.

Yes. Both the AD7655ASTZ and AD7654ASTZ are dual-channel SAR ADCs with two independent track-and-hold amplifiers that sample both inputs simultaneously, making them suitable for applications requiring phase-coherent acquisition such as motor control and power monitoring. The difference lies in throughput and power, not in the simultaneous-sampling architecture.

Both devices operate from a 5 V analog supply (AVDD) and a 2.7 V to 5.25 V digital supply (DVDD), and both support an external reference plus an internal reference option. The analog input range is configured via the reference and input span settings. Designers should confirm exact reference and supply limits in the respective Analog Devices datasheets, as the internal reference specifications and allowable input spans must be verified for each part.

Because the AD7655ASTZ runs at up to 1 MSPS and the AD7654ASTZ at up to 500 kSPS, the AD7655ASTZ typically dissipates more power at full rate. Both parts offer power-down modes to reduce consumption between conversions. Exact typical and maximum power figures should be taken from the official Analog Devices datasheets for each device, as they depend on supply voltages and throughput.

Not unconditionally. Although the package and pinout match, the AD7654ASTZ has a lower maximum throughput (500 kSPS versus 1 MSPS) and different timing and power characteristics. A drop-in replacement is only valid if the system's sampling rate, timing margins, and power budget are re-verified against the AD7654ASTZ datasheet. For new designs requiring 1 MSPS, the AD7655ASTZ should be specified.

Both devices provide a parallel interface and a serial interface for host communication, along with conversion start and busy/status signals. The parallel interface supports word-width readout, and the serial interface supports daisy-chaining in multi-converter systems. Specific timing and mode configuration details differ slightly and must be confirmed in each device's datasheet.