Part A
AD7654ASTZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 2675 PCS
- Package
- LQFP-48
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Replacement verdict
Not a drop-in replacement
The AD7654ASTZ and AD7651ASTZRL are both 16-bit successive-approximation ADCs from Analog Devices in the same 48-lead LQFP package, but they are not drop-in replacements. The AD7654ASTZ provides four analog input channels with simultaneous sampling, while the AD7651ASTZRL offers a single-channel configuration, so channel count and input architecture differ fundamentally. Their throughput rates, interface timing, and external component requirements also diverge, meaning a direct board-level substitution is not possible without redesign.
Different channel count
Different input architecture
Different throughput rate
Different interface timing
Parts at a glance
Part B
AD7651ASTZRL
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3821 PCS
- Package
- LQFP-48
- Series
- Acquisição de dados - Analogo para Convertedores Digitais (ADC)
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD7654ASTZ | AD7651ASTZRL | Why it matters |
|---|---|---|---|
| Number of ADC Channels | 2 (simultaneous sampling) | 1 | Determines how many analog signals can be digitized; the AD7654 supports two simultaneous channels while the AD7651 supports only one, affecting multi-signal acquisition designs. |
| Sampling Rate | 500 kSPS | 100 kSPS | Maximum throughput directly limits the bandwidth of signals that can be captured; the AD7654 is five times faster than the AD7651. |
| Resolution | 16 bits | 16 bits | Both provide 16-bit resolution, so dynamic range and quantization noise performance are comparable for a given input range. |
| Input Configuration | Pseudo-differential (2 channels) | Single-ended | Input topology affects common-mode rejection and wiring; pseudo-differential inputs reject ground noise better than single-ended inputs. |
| Interface Type | Parallel and Serial (SPI/QSPI/MICROWIRE/DSP) | Serial (SPI/QSPI/MICROWIRE/DSP) | The AD7654 offers both parallel and serial interfaces, allowing use with parallel-bus microcontrollers, while the AD7651 is serial-only. |
| Package / Pin Count | 48-lead LQFP | 48-lead LQFP | Package and pin count affect PCB footprint and layout; both use the same 48-lead LQFP, but pinouts differ due to interface differences. |
| Supply Voltage (Analog) | 5 V | 5 V | Analog supply defines the input voltage range and must match the system's analog front-end; both operate from a 5 V analog supply. |
| Power Consumption | Higher (dual-channel, 500 kSPS) | Lower (single-channel, 100 kSPS) | Power budget is critical in portable and dense systems; the faster dual-channel AD7654 consumes more power than the single-channel AD7651. |
| Internal Reference | Yes (2.5 V on-chip reference) | Yes (2.5 V on-chip reference) | An internal reference simplifies design by removing an external reference component; both devices include a 2.5 V reference. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7654ASTZ | AD7651ASTZRL |
|---|---|---|
| Supplier | - | Analog Devices Inc. |
| Series | PulSAR® | PulSAR® |
| Part Status | Active | Obsolete |
| Number of Bits | 16 | 16 |
| Sampling Rate(Per Second) | 500k | 100k |
| Number of Inputs | 2, 4 | 1 |
| Input Type | Pseudo-Differential, Single Ended | Pseudo-Differential |
| Data Interface | SPI, Parallel, DSP | SPI, Parallel, DSP |
| Configuration | MUX-S/H-MUX-ADC | S/H-ADC |
| Ratio - S / H: ADC | 2:1 | 1:1 |
| Number of A/D Converters | 1 | 1 |
| Architecture | SAR | SAR |
| Reference Type | External | External, Internal |
| Voltage - Supply, Analog | 5V | 5V |
| Voltage - Supply, Digital | 5V | 5V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Features | Simultaneous Sampling | - |
Frequently asked questions
What are the key differences between the AD7654ASTZ and AD7651ASTZRL?
The AD7654ASTZ is a dual-channel, 16-bit, 500 kSPS successive-approximation ADC, while the AD7651ASTZRL is a single-channel, 16-bit, 100 kSPS SAR ADC. The AD7654 provides two simultaneous-sampling inputs in a 48-lead LQFP, whereas the AD7651 offers one input in a 48-lead LQFP and is supplied in tape-and-reel form (RL suffix).
Are the AD7654ASTZ and AD7651ASTZRL pin-compatible?
No. Although both devices are offered in a 48-lead LQFP package, their pin functions differ because the AD7654 is a dual-channel converter and the AD7651 is a single-channel converter. The pinouts are not interchangeable, so PCB layouts must be designed for the specific part.
What are the resolution and throughput specifications of each device?
Both parts provide 16-bit resolution. The AD7654ASTZ offers a maximum throughput of 500 kSPS, while the AD7651ASTZRL offers a maximum throughput of 100 kSPS. The higher throughput of the AD7654 suits faster acquisition requirements, while the AD7651 targets lower-speed, lower-power applications.
How do the input configurations of the AD7654ASTZ and AD7651ASTZRL differ?
The AD7654ASTZ has two independent analog input channels that can be sampled simultaneously, making it suitable for applications requiring phase-coherent measurement of two signals. The AD7651ASTZRL has a single analog input channel, so it can only convert one signal at a time.
What are the power supply and interface requirements for these ADCs?
Both devices operate from a 5 V analog supply and a 2.7 V to 5.25 V digital supply, and both provide a parallel digital interface for connection to a host processor or DSP. Designers should confirm the exact supply and interface timing requirements in the respective manufacturer datasheets before finalizing a design.
What does the RL suffix on AD7651ASTZRL indicate?
The RL suffix denotes tape-and-reel packaging, which is intended for automated pick-and-place assembly in volume production. The AD7654ASTZ is supplied in standard tray or tube packaging. The electrical specifications of the AD7651ASTZRL are the same as the non-reel version of the AD7651ASTZ.
Can the AD7651ASTZRL be used as a drop-in replacement for the AD7654ASTZ?
No. The two devices differ in channel count, throughput, pinout, and package quantity, so they are not drop-in replacements. A redesign of the analog front end, PCB layout, and firmware timing would be required to substitute one for the other, and all differences must be validated against the manufacturer datasheets.