Analog Devices Inc. AD7651ACP

Overview

AD7651ACP from Analog Devices is a 16-bit, 100 kSPS charge redistribution SAR analog-to-digital converter operating from a single 5 V supply, featuring an internal 2.5 V reference (±7 ppm/°C drift), no pipeline delay, and dual parallel/serial (SPI/QSPI/MICROWIRE/DSP-compatible) interface. It delivers 86 dB SNR and 98 dB SFDR at 45 kHz input, targeting precision data acquisition in instrumentation and medical instruments.

For engineers reviewing the AD7651ACP datasheet, AD7651ACP pinout, AD7651ACP application, or AD7651ACP equivalent, key selection criteria include unipolar 0 V to 2.5 V input range, 16 mW typical power at 100 kSPS (without REF), 48-lead LQFP/LFCSP package compatibility, and support for both 3 V and 5 V logic interfaces.

Technical Context

The AD7651ACP implements a high-speed charge redistribution SAR architecture with integrated error correction circuitry and internal conversion clock, eliminating external timing components. Its analog front-end includes a track-and-hold with 2 ns aperture delay and 5 ps rms jitter, enabling accurate sampling of fast transients up to 800 kHz bandwidth.

Dual digital interface modes are hardware-selectable via SER/PAR pin: parallel 16-bit bus (D[15:0]) with RD/CS/BUSY control, or 2-wire serial mode supporting master/slave configurations, configurable clock polarity/inversion (INVSCLK), active-level SYNC (INVSYNC), and external/internal clock selection (EXT/INT).

Key Specifications

Pinout & Package

The AD7651ACP is available in a 48-lead LQFP (ST-48) and 48-lead LFCSP (CP-48) package, both rated for –40°C to +85°C operation. Pin functions are identical across packages; NC pins (3, 6, 7, 40) must remain unconnected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit SAR ADC applications.

Compared with AD7651ACP, AD7650ACPZ trades internal reference convenience for higher speed and pseudo-differential input, while ADS8860IDRCT offers faster throughput and lower voltage operation but lacks parallel interface and has higher reference drift-making AD7651ACP optimal for balanced precision, interface flexibility, and ease of use in 5 V systems.

Availability

AD7651ACP is available at Aetrix Electronics and suitable for data acquisition, instrumentation, and medical instruments requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for AD7651ACP includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA, with design centers worldwide.

The AD7651ACP belongs to Analog Devices' PulSAR® family of precision SAR ADCs, engineered for applications demanding high resolution, low latency, and integrated reference stability without sacrificing interface flexibility or power efficiency.

FAQ

What is the maximum recommended load capacitance for the AD7651ACP serial interface outputs?

The AD7651ACP serial interface (SYNC, SCLK, SDOUT) is characterized for CL ≤ 10 pF in serial modes; exceeding this value may violate timing specifications including t22 (SDOUT setup) and t23 (hold). For parallel mode operation, the maximum load is 60 pF. Always verify signal integrity with oscilloscope measurements under actual board conditions when using capacitive loads near these limits. The AD7651ACP datasheet specifies timing margins assuming worst-case 10 pF loading in serial configurations.

Does the AD7651ACP support true differential input operation?

No, the AD7651ACP is specified for unipolar pseudo-differential input only: IN relative to INGND, with common-mode range fixed at 0 V to 2.5 V. It does not support true differential inputs (e.g., IN+ and IN−) or bipolar ranges. Table 1 in the AD7651ACP datasheet explicitly lists it under "Pseudo-Differential" PulSAR devices, distinct from true differential models like AD7675 or AD7676. Attempting true differential connections violates absolute maximum ratings and invalidates specifications.

How does power dissipation change when using the internal reference versus an external reference on the AD7651ACP?

Using the internal reference increases AD7651ACP power dissipation by ~22 mW: 16 mW typical without REF versus 38 mW typical with REF enabled (PDREF = LOW, PDBUF = LOW). This reflects current drawn by the internal bandgap and buffer circuits. When external reference is used (PDREF = HIGH), the internal reference is disabled, reducing AVDD current by ~3 mA and enabling the 160 µW ultra-low-power mode at 1 kSPS. Power savings are measurable and documented in Table 2 of the AD7651ACP datasheet.

Can the AD7651ACP operate with OVDD = 3.3 V while AVDD and DVDD remain at 5 V?

Yes, the AD7651ACP supports mixed-supply operation: OVDD may be set to 3.3 V (within 2.7 V to 5.25 V range) independently of AVDD and DVDD (both 4.75 V to 5.25 V). This allows direct interfacing with 3.3 V microcontrollers or FPGAs without level translation. All digital interface timing parameters-including VOL/VOH levels and setup/hold times-are guaranteed across this OVDD range, as confirmed in the "Digital Outputs" and "Power Supplies" sections of the AD7651ACP datasheet.

What is the function of the TEMP pin on the AD7651ACP, and how is it calibrated?

The TEMP pin on the AD7651ACP provides an analog voltage proportional to die temperature: 300 mV at 25°C with 1 mV/°C sensitivity. It is factory-calibrated and requires no user trimming; output impedance is 4.3 kΩ, so low-impedance buffering is recommended before ADC measurement. This feature enables system-level thermal monitoring without adding discrete sensors-critical for medical and industrial applications where ambient and junction temperature tracking affects measurement accuracy. The AD7651ACP datasheet specifies TEMP performance across –40°C to +85°C.