Analog Devices Inc. LT1638HS8

Overview

LT1638HS8 from Analog Devices (formerly Linear Technology) is a dual rail-to-rail input and output operational amplifier with Over-The-Top® capability, enabling operation with inputs up to 44V above V– or above V+. It delivers 1.2MHz gain bandwidth, 0.4V/µs slew rate, and 25mA output drive while consuming only 170µA per amplifier at 3V supply. Designed for high-voltage micropower sensing in battery monitoring and supply current measurement.

For engineers reviewing the LT1638HS8 datasheet, LT1638HS8 pinout, LT1638HS8 application, or LT1638HS8 equivalent, key selection criteria include its –40°C to 125°C extended temperature rating, reverse-battery protection to 18V, rail-to-rail I/O swing, and verified Over-The-Top operation at 44V common-mode range - critical for industrial power rail monitoring and solar charge controllers.

Technical Context

The LT1638HS8 integrates dual independent amplifiers with separate NPN/PNP input stages, enabling seamless transition across the full 44V common-mode range without phase reversal. Its Over-The-Top architecture allows inputs to exceed V+ by up to 0.3V while maintaining valid output behavior, supported by internal Schottky clamping and phase-reversal protection circuitry.

It operates on single supplies from 2.7V to 44V total voltage or split supplies (±1.35V to ±22V), with reverse supply protection limiting current to <1nA at –18V. Input bias current remains stable across VCM (–14.7V to 29V), and output stage sustains rail-to-rail swing under 10mA load with <1.5V saturation at 5V supply.

Key Specifications

Pinout & Package

LT1638HS8 is packaged in an 8-lead plastic SO (S8) package with JEDEC MS-012AC outline, 1.27mm lead pitch, and exposed pad not present. Thermal resistance θ_JA = 190°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual rail-to-rail op amp applications.

Compared with LT1638IS8#TRPBF and ADA4077-2ARZ, the LT1638HS8 uniquely combines extended temperature operation, Over-The-Top input tolerance, and micropower consumption - making it irreplaceable in high-voltage, high-temperature embedded sensing where rail-to-rail I/O and reverse-battery survival are mandatory.

Availability

LT1638HS8 is available at Aetrix Electronics and suitable for battery monitoring systems, high-voltage supply current sensing, solar charge controller front-ends, and micropower active filters requiring stable component supply across extended temperature ranges.

Supply support for LT1638HS8 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, formed through the acquisition of Linear Technology in 2017.

The LT1638 product line was designed by Linear Technology specifically for micropower, high-voltage, rail-to-rail operational amplification in harsh-environment industrial and automotive applications - emphasizing Over-The-Top input robustness and reverse-battery survivability.

FAQ

What is the maximum common-mode input voltage range supported by the LT1638HS8?

The LT1638HS8 supports a common-mode input voltage range from 0.3V to 44V relative to V–, including operation with inputs above V+ (Over-The-Top®). This is validated across its full –40°C to 125°C operating temperature range and enables direct interfacing with 24V, 48V, and photovoltaic system rails without attenuation or level-shifting circuitry. The LT1638HS8 maintains specified performance up to 44V common-mode, with input differential voltage also rated to 44V.

Does the LT1638HS8 require external protection when used in reverse-battery configurations?

No, the LT1638HS8 does not require external protection in reverse-battery configurations. It incorporates integrated reverse-battery protection rated to –18V, drawing less than 1nA supply current under reverse supply conditions. This feature eliminates the need for series blocking diodes in automotive, solar, and backup power systems - preserving voltage headroom and reducing thermal dissipation. The protection is inherent to the LT1638HS8 silicon design and fully characterized across temperature.

Can the LT1638HS8 drive a 1000pF capacitive load without oscillation?

Yes, the LT1638HS8 can drive a 1000pF capacitive load without oscillation when using the recommended optional output compensation: a 0.22µF capacitor in series with a 150Ω resistor connected between the output and ground. This network stabilizes the amplifier's phase margin across all output currents and load conditions. Without this network, the LT1638HS8 is guaranteed stable only for capacitive loads ≤200pF. The compensation method is documented in the LT1638/LT1639 datasheet Figure 12 and applies identically to the LT1638HS8 variant.

What is the guaranteed input offset voltage specification for LT1638HS8 at 125°C?

The LT1638HS8 guarantees a maximum input offset voltage of 650µV at –40°C to 125°C for the SO package (S8), as specified in the "LT1638H/LT1639H" electrical characteristics table on page 6 of the datasheet. This value is measured under standard test conditions (VS = 3V, VO = 500mV to 2.5V, RL = 10kΩ) and represents the worst-case limit across temperature and process variation. At room temperature, typical VOS is 200µV, with drift limited to 15µV/°C maximum.

Is the LT1638HS8 pin-compatible with other members of the LT1638 family such as LT1638CS8?

Yes, the LT1638HS8 is fully pin-compatible with all other 8-lead SO-package variants of the LT1638, including LT1638CS8, LT1638IS8, and LT1638MS8. All share identical pinout (OUT A, –IN A, +IN A, V–, +IN B, –IN B, OUT B, V+), footprint, and solder pad layout per JEDEC MS-012AC. The only differences are temperature grade (H = –40°C to 125°C), initial offset voltage distribution, and guaranteed performance limits - allowing drop-in replacement in existing designs when extended temperature operation is required.