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Analog Devices Inc. LT1638CMS8
- Part No.:
- LT1638CMS8
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT1638CMS8.pdf
- Description:
- IC OPAMP GP 2 CIRCUIT 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,643
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Product details
Overview
LT1638CMS8 from Analog Devices (formerly Linear Technology) is a dual rail-to-rail input/output operational amplifier in an 8-lead MSOP package, featuring Over-The-Top® operation with inputs up to 44V above V–, 1.2MHz gain bandwidth, 0.4V/µs slew rate, and 170µA per amplifier quiescent current. It operates from 2.5V to 44V total supply, supports single- or split-supply configurations, and is reverse-battery protected to 18V - ideal for battery monitoring and high-side current sensing in industrial power systems.
For engineers reviewing the LT1638CMS8 datasheet, LT1638CMS8 pinout, LT1638CMS8 application, or LT1638CMS8 equivalent, key selection criteria include its guaranteed rail-to-rail I/O swing at 3V/5V/±15V supplies, ±25mA output drive capability, 98dB CMRR, 1500V/mV large-signal voltage gain, and validated performance across –40°C to +85°C without supply sequencing constraints.
Technical Context
The LT1638CMS8 integrates dual independent amplifiers with complementary NPN/PNP input stages enabling true Over-The-Top operation: either input can exceed V+ by up to 0.3V while maintaining phase reversal protection and 44V common-mode range relative to V–. Its internal compensation ensures unity-gain stability and drives ≥200pF capacitive loads directly; optional RC network extends stable operation to 1000pF.
Input bias current varies with common-mode voltage - typically –20nA below V+–0.8V (PNP active) and +40nA near V+ (NPN active), with built-in 1kΩ series resistors and clamping diodes preventing damage from inputs ≤2V below V–. Output stage delivers rail-to-rail swing (e.g., 3mV above V–, 20mV below V+ at no load) and sustains 25mA sourcing/sinking under full rail conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2.5V to 44V total - enables direct interface with 24V industrial buses and 44V battery stacks without level shifting. |
| Gain Bandwidth Product | 1.2MHz typical - supports stable closed-loop operation up to ~100kHz with moderate gain (e.g., G=10) in sensor signal chains. |
| Slew Rate | 0.4V/µs typical - sufficient for 10kHz full-scale sine waves at 4Vpp without distortion in micropower applications. |
| Input Common-Mode Range | –0.4V to 44V (single supply) - allows direct sensing of voltages above V+, e.g., high-side current sense on 44V rails. |
| Output Drive Current | ±25mA minimum - drives 2kΩ loads to rail while maintaining rail-to-rail swing, eliminating need for external buffers in transducer interfaces. |
| Quiescent Current | 170µA per amplifier - enables multi-year operation from coin cells in portable instrumentation and remote sensors. |
| CMRR | 98dB typical - rejects supply noise and ground bounce in noisy industrial environments when used in differential configurations. |
Pinout & Package
LT1638CMS8 uses the 8-lead plastic MSOP (MS8) package, 3.0mm × 3.0mm × 1.1mm body, with exposed pad internally connected to V– for thermal and electrical integrity. Pin 1 is marked by a dot or beveled corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OUT A) | Amplifier A output | Delivers rail-to-rail voltage with ±25mA drive; requires local 0.1µF bypass if driving >200pF. |
| 2 (–IN A) | Inverting input A | Protected by 1kΩ series resistor; accepts –0.4V to 44V common-mode; phase reversal protected. |
| 3 (+IN A) | Non-inverting input A | Same protection and voltage range as Pin 2; enables high-side sensing with reference to V+ or V–. |
| 4 (V–) | Negative supply / ground reference | Internally connects to exposed thermal pad; must be low-impedance for stability and thermal dissipation. |
| 5 (V+) | Positive supply | Bypass with 0.1µF ceramic capacitor within 25mm; reverse-battery protected to –18V. |
| 6 (+IN B) | Non-inverting input B | Independent channel with identical specs; supports dual-path signal conditioning or redundancy. |
| 7 (–IN B) | Inverting input B | Matches Pin 2 behavior; enables matched dual-channel configurations like instrumentation amps. |
| 8 (OUT B) | Amplifier B output | Electrically isolated from OUT A; shares same V+ and V– rails but has independent small-signal path. |
Key Features
| Feature | Design Value |
|---|---|
| Over-The-Top® Input Operation | Inputs function up to 44V above V– regardless of V+ - enables direct high-voltage rail monitoring without external dividers. |
| Rail-to-Rail Input and Output | Full dynamic range utilization from V– to V+ at both inputs and outputs - maximizes SNR in low-voltage (3V/5V) systems. |
| Reverse Battery Protection | Draws <1nA at –18V reverse supply - eliminates need for external blocking diodes in automotive and solar battery systems. |
| Unity-Gain Stable with Capacitive Loads | Drives ≥200pF directly; optional 150Ω + 0.22µF network extends stability to 1000pF - simplifies sensor cable interfacing. |
| No Supply Sequencing Requirement | Operates safely with V+ applied before or after V– - reduces system-level power-up complexity in multi-rail designs. |
Applications
| Battery Monitoring System | High-Side Current Sensing |
|---|---|
|
Use Scenario: Real-time monitoring of 12V–48V lead-acid or Li-ion battery packs in UPS and telecom power systems. IC Role / Device Role / Timing Role: Amplifier A measures cell voltage differentially; Amplifier B conditions shunt voltage with Over-The-Top input referenced to battery positive rail. Use Value: Eliminates external level shifters and high-voltage op amps - reduces BOM count and improves accuracy over temperature via rail-to-rail I/O. |
Use Scenario: Precision current measurement in motor drives and DC-DC converters where load connects to V+. IC Role / Device Role / Timing Role: Configured as non-inverting amplifier with gain set by precision resistors; inputs referenced to V+ enable sensing without ground disruption. Use Value: Achieves <1% error at 25°C using 0.2Ω shunt and 170µA quiescent current - extends runtime in portable test equipment. |
| Micropower Active Filter | 4mA–20mA Transmitter |
|
Use Scenario: Low-frequency anti-aliasing and noise filtering in wireless sensor nodes powered by CR2032 batteries. IC Role / Device Role / Timing Role: Dual-channel implementation of 2nd-order Sallen-Key low-pass filter; one amp as buffer, one as integrator. Use Value: 1.2MHz GBW supports 10kHz cutoff with minimal phase shift; 170µA/channel enables >5-year battery life at 100µA average system current. |
Use Scenario: Industrial loop-powered transmitter converting RTD or pressure sensor output to standardized 4mA–20mA analog signal. IC Role / Device Role / Timing Role: Amplifier A conditions sensor signal; Amplifier B serves as current-output stage with V– referenced to loop return. Use Value: Rail-to-rail output swing ensures full 16mA span utilization; reverse-battery protection prevents field wiring faults from damaging circuitry. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual rail-to-rail op amp applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1638IMS8#TRPBF | Identical electrical specs but rated for –40°C to +85°C industrial temperature grade (same MS8 package). | No functional difference; suitable for same applications where extended temp validation is required. | Select LT1638IMS8#TRPBF only if full industrial temp range testing and qualification documentation is mandated. |
| AD8602ARMZ | Lower quiescent current (120µA), higher GBW (8.4MHz), but limited input range (to V+ – 0.1V) and no Over-The-Top capability. | Not suitable for high-side sensing above V+ or 44V common-mode; better for low-noise, high-speed signal conditioning. | Choose AD8602ARMZ only when Over-The-Top operation is unnecessary and bandwidth >1MHz is critical. |
Compared with LT1638IMS8#TRPBF, the LT1638CMS8 offers identical performance at lower cost for commercial-grade applications; versus AD8602ARMZ, it trades bandwidth for unique high-voltage input flexibility and robustness in harsh supply environments.
Availability
LT1638CMS8 is available at Aetrix Electronics and suitable for battery monitoring, high-side current sensing, and micropower active filters requiring stable component supply across industrial and embedded OEM programs.
Supply support for LT1638CMS8 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 full product support, datasheets, and application engineering for legacy Linear parts including the LT1638 family.
The LT1638 product line was designed specifically for micropower, high-voltage rail-to-rail signal conditioning in space-constrained industrial and portable systems - emphasizing Over-The-Top operation, reverse-battery resilience, and wide supply tolerance.
FAQ
What is the maximum input voltage range supported by the LT1638CMS8?
The LT1638CMS8 supports an input common-mode voltage range from –0.4V to 44V relative to V–, independent of V+. This Over-The-Top® capability allows either input to exceed V+ by up to 0.3V while remaining fully functional - a key feature confirmed in the Simplified Schematic and Absolute Maximum Ratings table. The LT1638CMS8 thus enables direct interface with 44V battery stacks or industrial bus voltages without external attenuation.
Does the LT1638CMS8 require external compensation for driving capacitive loads?
The LT1638CMS8 is internally compensated to drive ≥200pF capacitively without oscillation. For loads exceeding 200pF - such as long cables or piezoelectric sensors - optional external compensation using a 150Ω resistor in series with a 0.22µF capacitor from output to ground extends stable operation to 1000pF, as verified in the Applications Information section and Typical Performance Characteristic G22. No compensation is needed for standard PCB traces or short sensor connections.
Can the LT1638CMS8 operate with a single 3V supply?
Yes, the LT1638CMS8 is fully specified and characterized for 3V single-supply operation (V+ = 3V, V– = 0V), with guaranteed rail-to-rail input and output swing, 1.2MHz gain bandwidth, and 170µA quiescent current per amplifier. Electrical Characteristics tables explicitly list parameters at VS = 3V, including output swing (e.g., VOL = 250mV max at 5mA sink), CMRR (88dB), and PSRR (90dB), confirming robust low-voltage functionality.
How does the LT1638CMS8 handle reverse battery connection?
The LT1638CMS8 incorporates reverse battery protection up to –18V on V+, drawing less than 1nA supply current during fault conditions - verified in the Absolute Maximum Ratings and Applications Information sections. This eliminates the need for external series diodes in automotive or solar battery applications, preserving voltage headroom and reducing thermal losses. The protection remains active even when inputs are biased 44V above V–.
Is the LT1638CMS8 pin-compatible with other packages in the LT1638 family?
No - the LT1638CMS8 (MS8 package) shares identical pinout with the LT1638CN8 (PDIP) and LT1638CS8 (SO), but differs from the LT1638CDD (DFN) which has V– connected to the exposed pad and rearranged pin numbering. The MS8, PDIP, and SO variants use the same 8-pin configuration shown in the Pin Configuration diagram (Page 3), while DFN places V– on the underside thermal pad and reorders pins 4/5. Always verify package-specific layout per LTC DWG #05-08-1660 Rev F.
LT1638CMS8 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Amplifier Type:
- General Purpose
- Number of Circuits:
- 2
- Output Type:
- Rail-to-Rail
- Slew Rate:
- 0.4V/µs
- Gain Bandwidth Product:
- 1.2 MHz
- -3db Bandwidth:
- -
- Current - Input Bias:
- 20 nA
- Voltage - Input Offset:
- 400 µV
- Current - Supply:
- 205µA (x2 Channels)
- Current - Output / Channel:
- 40 mA
- Voltage - Supply Span (Min):
- 2.5 V
- Voltage - Supply Span (Max):
- 44 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP
LT1638CMS8 FAQ
1.How can I place an order for LT1638CMS8 through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1638CMS8 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LT1638CMS8 reliable?
The price and inventory of LT1638CMS8 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1638CMS8 is usually 5 days.
3.What payment methods are accepted for LT1638CMS8?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1638CMS8 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1638CMS8?
LT1638CMS8 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1638CMS8 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LT1638CMS8?
For technical support, including LT1638CMS8 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1638CMS8 requirements.
6.How does Aetrix verify that LT1638CMS8 is sourced from the original manufacturer or authorized distributors?
All LT1638CMS8 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LT1638CMS8 meets industry standards.
7.What is the process for return or replacement of LT1638CMS8?
All LT1638CMS8 units undergo pre-shipment inspection (PSI). If there is an issue with LT1638CMS8, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LT1638CMS8 part is unused and in its original packaging.
Return procedure for LT1638CMS8:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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