Analog Devices Inc. LTC1408CUH-12#PBF

Overview

LTC1408CUH-12 from Analog Devices (formerly Linear Technology) is a 12-bit, 600ksps simultaneous-sampling analog-to-digital converter with six differential input channels, 72dB SINAD, 83dB CMRR, and 3V single-supply operation in a 32-pin 5mm × 5mm QFN package. It supports unipolar (0V–2.5V) or bipolar (±1.25V) differential input ranges and is used in multiphase power measurement and motor control systems requiring precise phase-aligned acquisition.

For engineers reviewing the LTC1408CUH-12 datasheet, LTC1408CUH-12 pinout, LTC1408CUH-12 application, or LTC1408CUH-12 equivalent, key selection criteria include simultaneous sampling capability, 100ksps per-channel throughput, SLEEP mode (6µW), SPI-compatible serial interface, and 32-pin QFN thermal performance for portable and space-constrained industrial designs.

Technical Context

The LTC1408CUH-12 employs six independent sample-and-hold circuits triggered synchronously on the rising edge of the CONV signal, enabling true simultaneous sampling across all six differential pairs. Its internal 2.5V bandgap reference (±15ppm/°C tempco) supports both unipolar and bipolar modes via the BIP pin, with output data formatted as straight binary or 2's complement respectively.

Conversion sequencing is controlled by SEL2/SEL1/SEL0, allowing dynamic selection of 1–6 channels per conversion cycle (96 SCLK max). The 3-wire SPI-compatible serial interface outputs 12-bit words MSB-first over SDO, with timing guaranteed for tSCK ≥ 100ns and tTHROUGHPUT = 10µs minimum at full rate.

Key Specifications

Pinout & Package

Package: 32-pin plastic QFN (5mm × 5mm), exposed pad (Pin 33) soldered to PCB ground for thermal and electrical integrity. θJA = 34°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS8686SIPWR and AD7656ASTZ, the LTC1408CUH-12 uniquely balances 12-bit simultaneous sampling, 6µW SLEEP mode, and 5mm × 5mm QFN size - making it optimal for space- and power-sensitive industrial DAQ where 12-bit fidelity suffices.

Availability

LTC1408CUH-12 is available at Aetrix Electronics and suitable for multiphase power measurement, motor control, and uninterruptible power supplies requiring stable component supply, long-term lifecycle support, and traceable sourcing for industrial OEM programs.

Supply support for LTC1408CUH-12 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 acquired Linear Technology in 2017 and maintains its high-performance precision analog portfolio, emphasizing signal chain integrity, low-noise design, and industrial reliability.

The LTC1408CUH-12 belongs to Linear's simultaneous-sampling ADC family, engineered for applications demanding phase-coherent acquisition across multiple channels - especially in power electronics, motor drives, and energy monitoring systems.

FAQ

What is the operating temperature range for the LTC1408CUH-12?

The LTC1408CUH-12 is rated for 0°C to 70°C ambient operation, matching the 'C' grade specification. This makes it suitable for commercial and industrial indoor applications where ambient temperatures remain within this range. The device's thermal resistance (θJA = 34°C/W) and low 15mW active power dissipation ensure stable performance without forced cooling in typical enclosures. For extended temperature operation, the LTC1408IUH-12 (–40°C to 85°C) is the qualified alternative.

How does the LTC1408CUH-12 achieve simultaneous sampling across six channels?

The LTC1408CUH-12 achieves true simultaneous sampling using six independent sample-and-hold (S&H) circuits, all triggered by the rising edge of the CONV signal. Each S&H captures its respective differential input (CH0+/- through CH5+/-) at the exact same instant, eliminating inter-channel timing skew. Aperture skew is specified at ≤200ps, ensuring phase coherence critical for vector calculations in power and motor control. The subsequent conversion proceeds sequentially per enabled channel under SCK control.

Can the LTC1408CUH-12 use an external reference, and what are the voltage limits?

Yes, the LTC1408CUH-12 supports external reference override via the VREF pin (Pin 23). The external reference voltage must be between 2.55V and VDD (max 4V), and it replaces the internal 2.5V bandgap reference. This allows improved absolute accuracy, lower tempco (±1ppm/°C with precision references), or system-level calibration. When using an external reference, the internal reference is disabled, and the 10µF bypass capacitor remains required for stability.

What is the minimum acquisition time, and how does source impedance affect it?

The LTC1408CUH-12 specifies a 39ns acquisition time under ideal conditions (low-impedance source). As source impedance increases, acquisition time lengthens due to RC time constant effects on the internal sampling capacitor. For sources >100Ω, a buffer amplifier with low output impedance and ≥40MHz small-signal bandwidth is recommended to maintain full 100ksps per-channel throughput and avoid code-dependent errors.

How do SEL2/SEL1/SEL0 control the number of converted channels?

SEL2/SEL1/SEL0 (Pins 26–28) form a 3-bit code that determines how many of the six channels are converted per cycle: 000 = CH0 only; 001 = CH0–CH1; 010 = CH0–CH2; 011 = CH0–CH3; 100 = CH0–CH4; 101/110/111 = all six channels. The selected channels are converted sequentially after simultaneous sampling, reducing total conversion time - e.g., 3 channels require only 48 SCLK cycles instead of 96.