Texas Instruments LMH32401-Q1

Overview

LMH32401-Q1 from Texas Instruments is an AEC-Q100 Grade 1 automotive transimpedance amplifier (TIA) with programmable gain (2 kΩ or 20 kΩ), 450-MHz bandwidth at low gain, differential output drive capability, and integrated ambient light cancellation. It serves as the front-end signal conditioner in LIDAR receiver chains, converting photodiode current to high-speed differential voltage for ADC interfacing.

For engineers reviewing the LMH32401-Q1 datasheet, LMH32401-Q1 pinout, LMH32401-Q1 application, or LMH32401-Q1 equivalent, key selection considerations include gain-switching transient behavior, input-referred noise (250 nARMS at 2 kΩ), overload recovery via 100-mA clamp, differential output swing (1.5 VPP into 100 Ω), and wettable-flank VQFN package suitability for automotive optical sensing PCBs.

Technical Context

The LMH32401-Q1 implements a single-ended-input, differential-output TIA architecture with two discrete transimpedance gain settings controlled by the GAIN pin. Its closed-loop bandwidth scales inversely with gain: 450 MHz at 2 kΩ and 275 MHz at 20 kΩ, both measured with 1-pF photodiode capacitance and 100-Ω load.

It integrates three critical system-level functions: ambient light cancellation (ALC) loop with µs-scale settling, 100-mA output clamp for rapid overload recovery, and output multiplexing via EN pin control-enabling time-division multiplexing of multiple TIAs onto a shared ADC channel without external switches.

Key Specifications

Pinout & Package

LMH32401-Q1 is housed in a 3 mm × 3 mm, 16-pin wettable-flank VQFN (RGT) package with exposed thermal pad. The package supports automated optical inspection (AOI) and improves solder joint reliability in automotive thermal cycling environments.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transimpedance amplifier applications.

Compared with LMH32402-Q1 and OPA858QDGKRQ1, the LMH32401-Q1 uniquely combines automotive qualification, differential output, integrated ALC, and overload protection in a single-channel wettable-flank package-making it the only drop-in solution for production automotive LIDAR front ends requiring functional safety and optical robustness.

Availability

LMH32401-Q1 is available at Aetrix Electronics and suitable for mechanically scanning LIDAR, solid-state scanning LIDAR, and industrial robot LIDAR requiring stable component supply, AEC-Q100 compliance, and high-volume automotive traceability.

Supply support for LMH32401-Q1 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

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in high-performance signal chain and power management ICs for automotive, industrial, and communications markets.

The LMH32401-Q1 belongs to TI's automotive LIDAR signal chain portfolio, designed specifically to replace discrete TIA + driver + protection circuits with a single-IC, AEC-Q100-compliant solution that simplifies optical receiver design and improves time-of-flight measurement accuracy.

FAQ

What is the maximum photodiode capacitance supported by LMH32401-Q1 at 450-MHz bandwidth?

The LMH32401-Q1 achieves its rated 450-MHz small-signal bandwidth at gain = 2 kΩ with 1-pF photodiode capacitance (CPD). Performance degrades with higher CPD: at 2 pF, bandwidth drops to ~380 MHz; at 4.7 pF, it falls to ~270 MHz. Layout best practices require minimizing trace capacitance and using low-C PDs or pre-compensation techniques for >1-pF sources.

How does the ambient light cancellation (ALC) loop affect LMH32401-Q1 noise performance?

Enabling the ALC loop adds measurable noise to the LMH32401-Q1 signal path, as documented in the datasheet. At gain = 2 kΩ and CPD = 1 pF, input-referred noise increases from 250 nARMS (ALC disabled) to approximately 280 nARMS (ALC enabled, IDC = 100 µA). This trade-off is intentional: the loop's ability to cancel up to 3 mA of ambient current outweighs the modest SNR penalty in sunlit outdoor LIDAR operation.

Can LMH32401-Q1 drive a 50-Ω differential load instead of the specified 100 Ω?

Yes, the LMH32401-Q1 can drive a 50-Ω differential load, but output swing and gain will change. Driving 50 Ω reduces differential output swing from 1.5 VPP to ~1.2 VPP and increases transimpedance gain by ~10% (e.g., 2.2 kΩ instead of 2 kΩ at low gain). Ensure the downstream ADC input impedance and termination scheme accommodate this shift to avoid signal reflection or clipping.

What is the purpose of the VOCM and VOD pins on LMH32401-Q1, and how are they typically configured?

The VOCM pin sets the common-mode voltage of the differential output (typically 1.1 V), while VOD adjusts the differential offset (VOUT− − VOUT+). In most LIDAR designs, VOCM is driven to 1.1 V with a precision voltage source or resistor divider, and VOD is grounded or set to 0.5 V to center the output around 0 V differential. Both pins support active control for dynamic calibration but are often fixed for production simplicity.

Does LMH32401-Q1 support simultaneous operation of multiple units sharing one ADC input?

Yes, the LMH32401-Q1 supports time-division multiplexing via its EN pin. When EN is high, the amplifier enters shutdown mode and its outputs go high-impedance. By synchronizing EN signals across multiple LMH32401-Q1 units, designers can sequentially route each channel's output to a single ADC without external analog switches-reducing component count, board area, and signal path mismatch in multi-zone LIDAR receivers.