Analog Devices Inc. DC887A

Overview

LTC1408 from Analog Devices (formerly Linear Technology) is a 14-bit, 6-channel simultaneous-sampling analog-to-digital converter with 600ksps aggregate throughput and 100ksps per channel. It operates from a single 3V supply, draws only 5mA active current, and features 90dB common-mode rejection for differential signal acquisition in noisy environments - ideal for multiphase power measurement and motor control systems.

For engineers reviewing the LTC1408 datasheet, LTC1408 pinout, LTC1408 application, or LTC1408 equivalent, key selection criteria include simultaneous sampling capability across six differential inputs, 76dB SINAD at 100kHz, SLEEP mode (6µW), 32-pin 5mm × 5mm QFN package, and configurable unipolar/bipolar input range via BIP pin.

Technical Context

The LTC1408 implements six independent sample-and-hold circuits triggered synchronously on the rising edge of CONV, enabling true simultaneous capture of all six differential input pairs. Conversion proceeds sequentially per enabled channel using a shared 14-bit SAR core, with timing controlled by external SCK (up to 10MHz).

It supports flexible channel selection (1–6 channels) via SEL2/SEL1/SEL0, bipolar/unipolar mode via BIP, and internal 2.5V reference (±15ppm/°C tempco) that can be overdriven by an external reference. The 3-wire serial interface outputs MSB-first data in 96-clock bursts for full 6-channel reads.

Key Specifications

Pinout & Package

Package: 32-pin plastic QFN (5mm × 5mm), exposed thermal pad (Pin 33) soldered to PCB ground plane.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar simultaneous-sampling ADC applications.

Compared with ADS8588S and AD7656A-1, the LTC1408 offers the lowest power-per-channel (2.5mW) and smallest footprint (5mm × 5mm) while maintaining 14-bit fidelity and true simultaneity - making it optimal for space- and battery-constrained embedded power electronics.

Availability

LTC1408 is available at Aetrix Electronics and suitable for multiphase motor control, uninterruptible power supplies, and portable data acquisition systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LTC1408 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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LTC1408 belongs to ADI's precision data acquisition portfolio, designed specifically for applications demanding synchronized multichannel sampling with low power and small size - especially in energy-efficient power conversion and real-time motor control.

FAQ

What is the maximum sampling rate per channel for the LTC1408?

The LTC1408 achieves 100ksps per channel when all six channels are enabled, resulting in a total aggregate sampling rate of 600ksps. This is achieved through simultaneous sampling followed by sequential conversion, with each enabled channel requiring 16 SCK cycles - 96 clocks for full 6-channel readout. The minimum SCK period is 100ns (10MHz max), and timing is guaranteed over the full operating temperature range.

How does the BIP pin affect output data format in the LTC1408?

The BIP pin on the LTC1408 directly controls both input range and output coding: when BIP = LOW, the device accepts 0V–2.5V differential inputs and outputs straight binary data; when BIP = HIGH, it accepts ±1.25V differential inputs and outputs 2's complement data. The BIP state must remain fixed during conversion and readout; changing it between conversions requires allowing full acquisition time before the next CONV pulse to avoid invalid codes.

Can the LTC1408 use an external reference, and what are the voltage limits?

Yes, the LTC1408 can overdrive its internal 2.5V reference using an external source applied to the VREF pin. The acceptable external reference voltage range is 2.55V to VDD (with VDD between 2.7V and 3.6V). Using an external reference improves accuracy and tempco - e.g., a precision 2.5V reference with ±1ppm/°C drift reduces overall system error versus the internal ±15ppm/°C reference. The internal reference remains active unless overdriven.

What is the channel-to-channel aperture skew specification for the LTC1408?

The LTC1408 specifies a maximum channel-to-channel aperture skew of 200ps, measured as the timing mismatch between the effective sampling instants of any two channels. This ultra-low skew is enabled by six independent, identically biased sample-and-hold circuits triggered by a single CONV edge - ensuring phase coherence critical for power quality analysis and FOC algorithms. Skew is guaranteed over the full –40°C to +85°C temperature range.

How do SEL2, SEL1, and SEL0 configure channel selection in the LTC1408?

SEL2/SEL1/SEL0 are binary-encoded inputs that determine how many of the six channels are converted and output per cycle: 000 enables only CH0; 001 enables CH0–CH1; up to 101/110/111 which all enable all six channels. These pins must remain static during conversion and subsequent readout. Changing SELx between conversions allows dynamic channel grouping - e.g., reading CH0–CH3 first, then CH4–CH5 - without reconfiguring hardware connections.