Texas Instruments OPA3S2859MRTWREP

Overview

OPA3S2859MRTWREP from Texas Instruments is a dual-channel, radiation-hardened, programmable-gain transimpedance amplifier (TIA) optimized for photodiode-based high-speed optical sensing. It delivers 900-MHz gain-bandwidth product, 2.2-nV/√Hz input voltage noise, and 350-V/μs slew rate across –55°C to +125°C, enabling precision laser distance measurement and OTDR front ends.

For engineers reviewing the OPA3S2859MRTWREP datasheet, OPA3S2859MRTWREP pinout, OPA3S2859MRTWREP application, or OPA3S2859MRTWREP equivalent, key selection criteria include transimpedance bandwidth vs. feedback resistor selection (1 kΩ/10 kΩ/100 kΩ), latch-controlled gain stability per channel, power-down quiescent current (75 μA), and WQFN-24 thermal pad layout requirements.

Technical Context

The OPA3S2859MRTWREP integrates three switched feedback paths per channel-FB_A0/FB_A1/FB_A2 and FB_B0/FB_B1/FB_B2-enabling four discrete transimpedance gains (<10 kΩ, 10–100 kΩ, >100 kΩ, or external). Each switch pair (COM + FB) is independently optimized for on-resistance (RON_COM0 = 80 Ω, RON_FB0 = 38 Ω) and parasitic capacitance (CCOM0 = 1.3 pF, CFB0 = 1.9 pF) to preserve bandwidth in low-capacitance photodiode interfaces.

Gain selection uses a 2-wire parallel interface (SEL0/SEL1) with independent latch control (LTCH_A/LTCH_B) to freeze gain configuration per channel. Power-down mode reduces total quiescent current to 75 μA while maintaining fast turn-on (90 ns) and turn-off (330 ns) timing-critical for pulsed optical systems requiring duty-cycled amplification.

Key Specifications

Pinout & Package

OPA3S2859MRTWREP is housed in a 4.00 mm × 4.00 mm, 24-pin WQFN package with exposed thermal pad connected to VS− (pins 13 and 18) for optimal heat dissipation in high-power-density designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA657IDBVR and LMH6629MA/NOPB, the OPA3S2859MRTWREP uniquely combines dual-channel operation, on-chip programmable gain switching, per-channel latching, and radiation-hardened EP qualification-making it the only solution for space-grade, multi-range, time-gated optical receivers requiring guaranteed long-term availability and traceability.

Availability

OPA3S2859MRTWREP is available at Aetrix Electronics and suitable for laser distance measurement, optical time domain reflectometry (OTDR), and silicon photomultiplier (SiPM) buffer applications requiring stable component supply across extended product lifecycles and extreme environmental conditions.

Supply support for OPA3S2859MRTWREP 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 leader specializing in analog and embedded processing technologies, with deep expertise in high-performance amplifiers and radiation-tolerant components for mission-critical systems.

The OPA3S2859MRTWREP belongs to TI's Enhanced Product (EP) amplifier portfolio, engineered specifically for defense, aerospace, and medical applications demanding extended temperature operation, controlled manufacturing baselines, and full product traceability.

FAQ

What is the maximum transimpedance bandwidth achievable with OPA3S2859MRTWREP?

The OPA3S2859MRTWREP achieves up to 130 MHz small-signal transimpedance bandwidth when configured with 1-kΩ feedback resistance and 4-pF total input capacitance (photodiode + PCB). This value is measured at 100-mVPP output swing and reflects the device's 900-MHz gain-bandwidth product applied to low-capacitance photodiode interfaces. Bandwidth decreases predictably with higher RF values: 40 MHz at 10 kΩ and 14 MHz at 100 kΩ.

How does the latch function work on OPA3S2859MRTWREP?

The OPA3S2859MRTWREP provides independent latch control via LTCH_A and LTCH_B pins. When LTCH_A is driven low, Channel A's gain configuration becomes immune to changes on SEL0/SEL1-locking the currently selected feedback path (e.g., FB_A1). This prevents unintended gain switching due to digital noise or timing skew. The latch remains active until LTCH_A is returned high, restoring transparent gain control. Same behavior applies to Channel B via LTCH_B.

Can OPA3S2859MRTWREP operate from a single 3.3-V supply?

Yes, OPA3S2859MRTWREP supports single-supply operation from 3.3 V (VS+ = 3.3 V, VS− = 0 V) across its full –55°C to +125°C temperature range. Input common-mode range extends from 0 V to 1.9 V (VIH), and output swing reaches 1.0 V to 2.4 V (VOL to VOH) under these conditions. Quiescent current drops to ~39–47 mA, and power-down mode still achieves 75–170 μA, making it viable for portable or battery-constrained optical sensors.

What is the purpose of the multiple FB and COM pins on OPA3S2859MRTWREP?

OPA3S2859MRTWREP includes three dedicated FB pins (FB_A0–FB_A2, FB_B0–FB_B2) and corresponding COM pins (COM_A, COM_B) per channel to implement internally switched transimpedance gain paths. Each FB/COM pair is optimized for a specific feedback resistor range (<10 kΩ, 10–100 kΩ, >100 kΩ) with tailored on-resistance and parasitic capacitance. This eliminates external switches or relays, reducing board area, insertion loss, and layout-induced bandwidth degradation in high-frequency optical front ends.

Is OPA3S2859MRTWREP pin-compatible with other TI transimpedance amplifiers?

No, OPA3S2859MRTWREP is not pin-compatible with other TI transimpedance amplifiers such as OPA657 or LMH6629. Its 24-pin WQFN package features unique pin assignments-including six FB pins, two COM pins, dual latch inputs, and separate SEL0/SEL1 controls-that support its integrated programmable gain architecture. Migration requires PCB redesign and layout optimization for thermal pad grounding and high-frequency signal integrity.