Analog Devices Inc. AD7858ANZ

Overview

AD7858ANZ from Analog Devices is a 12-bit, 200 kSPS SAR analog-to-digital converter with eight single-ended or four pseudo-differential inputs, internal reference buffer, and flexible SPI/QSPI/μP-compatible serial interface. It operates from a single 3 V to 5.5 V supply, delivers ±1 LSB integral nonlinearity, and supports system/self-calibration - used in portable medical instruments and high-speed modem front-ends.

For engineers reviewing the AD7858ANZ datasheet, AD7858ANZ pinout, AD7858ANZ application, or AD7858ANZ equivalent, this page provides verified technical context, real-world timing behavior, calibrated DC accuracy specs, package-specific thermal data, and validated alternative options for battery-powered and industrial signal acquisition designs.

Technical Context

The AD7858ANZ implements a charge redistribution DAC-based SAR architecture with integrated track-and-hold, on-chip 2.5 V reference buffer (REFIN/REFOUT), and dual-domain power supplies (AVDD/DVDD). Its conversion cycle begins on CONVST rising edge, completes in ≤4.6 µs at 4 MHz CLKIN, and asserts BUSY until result is latched.

It features programmable channel configuration (SGL/DIFF bit), three power management modes (normal/sleep/full power-down), and register-controlled calibration sequencing (self/system offset/gain) via 16-bit serial interface with SYNC framing. All digital I/O meets 3 V/5 V logic thresholds with 4 ns–130 ns timing margins per interface mode.

Key Specifications

Pinout & Package

AD7858ANZ is supplied in a 24-lead plastic DIP (N-24) package with 0.3-inch body width, θ_JA = 105°C/W, and rated for –40°C to +85°C operation. Pin 1 is CONVST; pin 24 is SYNC; pins 9–16 are AIN1–AIN8; pin 17 is CAL; pin 4 is REFIN/REFOUT.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit SAR ADC applications.

Compared with AD7858BNZ, the AD7858ANZ trades 0.5 LSB INL tolerance for broader A-grade availability and lower unit cost; compared with AD7858LANZ, it doubles throughput at the expense of ~2× power consumption - making AD7858ANZ optimal for performance-critical, thermally managed systems.

Availability

AD7858ANZ is available at Aetrix Electronics and suitable for portable medical instrumentation, industrial data acquisition, high-speed modem front-ends, and pen-based computing interfaces requiring stable component supply and long-term production continuity.

Supply support for AD7858ANZ 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 and ISO 9001-certified manufacturing.

The AD7858 series belongs to Analog Devices' precision SAR ADC product line, engineered for low-power, high-accuracy data acquisition in battery-constrained and thermally sensitive applications - emphasizing calibration robustness, supply flexibility, and serial interface interoperability.

FAQ

What is the maximum sample rate supported by the AD7858ANZ?

The AD7858ANZ achieves a maximum throughput rate of 200 kSPS under standard conditions (4 MHz CLKIN, AVDD/DVDD = 3.0 V to 5.5 V). This is confirmed in the General Description and Timing Specifications sections of the datasheet, where conversion time is specified as ≤4.6 µs. The AD7858ANZ does not support higher rates - exceeding 200 kSPS would violate timing margins and invalidate DC accuracy guarantees. For applications requiring sustained 200 kSPS operation, ensure BUSY polling or interrupt handling aligns with this timing constraint.

Does the AD7858ANZ require external reference components?

No, the AD7858ANZ integrates an internal 2.5 V reference buffer accessible via the REFIN/REFOUT pin, eliminating the need for an external reference IC. However, two external capacitors are mandatory: a 0.1 µF multilayer ceramic (CREF1) and a 0.01 µF ceramic disc (CREF2), both connected between their respective pins (7 and 8) and AGND. These stabilize the internal DAC's charge redistribution network and are explicitly required in the Pin Function Descriptions and Typical Application Circuit. Omitting either capacitor degrades INL and increases noise.

How does the AD7858ANZ handle power-down and wake-up sequences?

AD7858ANZ supports three power states controlled by the SLEEP pin and PMGT bits in the Control Register. Asserting SLEEP = 0 enters sleep mode (5 µA max with clock off); releasing SLEEP returns to normal operation within one CLKIN cycle. Full power-down (including reference shutdown) occurs automatically after conversion unless overridden by PMGT settings. Wake-up is immediate - no stabilization delay is required because calibration data is retained and the internal reference re-enables synchronously with AVDD/DVDD. This behavior is documented in the Power-Down section and Absolute Maximum Ratings.

Can the AD7858ANZ interface directly with an 8051 microcontroller?

Yes, the AD7858ANZ serial interface is explicitly designed to be compatible with 8051-family controllers, as stated in the FEATURES and PRODUCT HIGHLIGHTS sections. It uses standard SPI-like signaling (SYNC, SCLK, DIN, DOUT) with configurable frame synchronization and supports MSB-first 16-bit transfers. Timing parameters such as t7 (data setup before SCLK↑) and t8 (data hold after SCLK↑) are specified for 3 V and 5 V logic levels, ensuring reliable communication with 8051 I/O ports without level-shifting. No special firmware drivers are needed beyond standard bit-banged or hardware SPI peripheral configuration.

What is the purpose of the CAL pin on the AD7858ANZ?

The CAL pin (Pin 17) serves as the primary hardware trigger for on-chip calibration. A rising edge initiates self-calibration; a falling edge resets calibration logic. Internally pulled up, it can be tied high for normal operation or connected to a 10 nF capacitor to DGND to enable automatic self-calibration on power-up. This function is independent of software register writes and takes precedence over all other operations - as confirmed in the PIN FUNCTION DESCRIPTIONS and CALIBRATION section. The CAL pin does not provide status feedback; BUSY must be monitored to detect calibration completion.