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Texas Instruments LMP91200MT/NOPB
- Part No.:
- LMP91200MT/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Sensor and Detector Interfaces
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LMP91200MT/NOPB.pdf
- Description:
- IC AFE PH SENSOR 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:248
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Product details
Overview
LMP91200MT/NOPB from Texas Instruments is a configurable analog front-end (AFE) IC designed specifically for low-power, high-impedance pH sensor interfacing in analytical instrumentation. It integrates a pH buffer with ±125 fA input bias current (25°C), 16-pin TSSOP package, and operates from 1.8 V to 5.5 V supply across –40°C to +125°C - enabling precision measurement in portable water quality analyzers and industrial process control systems.
For engineers reviewing the LMP91200MT/NOPB datasheet, LMP91200MT/NOPB pinout, LMP91200MT/NOPB application, or LMP91200MT/NOPB equivalent, key selection criteria include ultra-low input bias current for minimal electrode loading, active guarding support via GUARD1/GUARD2 pins, integrated VCM/VCMHI buffering for common-mode stability, and guaranteed operation over extended temperature range without external calibration circuitry.
Technical Context
The LMP91200MT/NOPB implements a dedicated pH buffer stage with unity gain and sub-femtoampere input bias current, optimized for 2-electrode pH sensors with output impedances up to 1 GΩ. Its architecture includes dual guard outputs (GUARD1/GUARD2) referenced to INP potential, eliminating need for external op-amps in guard-ring implementation.
It features three functional blocks: pH buffer (INP → VOUT), VCM buffer (VCMHI/VCM/VOCM), and programmable-gain amplifier (PGA) with fixed 5× gain. All stages share common 1.8–5.5 V supply and operate with 50 µA total quiescent current during pH measurement mode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Bias Current (INP) | ±125 fA max at 25°C - ensures <1.25 µV error with 10 MΩ electrode impedance |
| Input Offset Voltage | ±200 µV - contributes <0.0035 pH error at 25°C using Nernst slope (59.16 mV/pH) |
| Supply Current | 50 µA in pH measurement mode - enables multi-year battery life in portable meters |
| Supply Voltage Range | 1.8 V to 5.5 V - supports single-cell Li-ion, coin cell, or 3.3 V/5 V system rails |
| Operating Temperature | –40°C to +125°C - qualified for harsh industrial and outdoor environmental monitoring |
| Package | 16-pin TSSOP (5.00 mm × 4.40 mm) - surface-mount compatible with automated PCB assembly |
Pinout & Package
Package: 16-pin TSSOP (PW), body size 5.00 mm × 4.40 mm, exposed pad not present, RoHS-compliant lead finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VDD | Positive power supply | Main analog/digital supply rail; requires local 10 µF/1 µF/0.1 µF decoupling |
| 4 GUARD1 | Active guard output | Drives guard ring at INP potential to suppress leakage currents on high-Z traces |
| 5 INP | pH sensor noninverting input | High-impedance node accepting ±415 mV signal from pH electrode vs. VCM reference |
| 6 GUARD2 | Active guard output | Second guard output for dual-layer PCB guard rings or triaxial cable shielding |
| 7 VCMHI | High-impedance common-mode output | Unbuffered VCM copy for differential ADC reference or external feedback networks |
| 8 VCM | Buffered common-mode output | Low-impedance internal zero reference; connects directly to pH electrode's reference terminal |
| 9 VREF | Voltage reference input | Accepts external 1.8–5 V reference for PGA gain scaling and offset calibration |
| 10,13,15,16 GND | Analog ground | Four dedicated GND pins minimize ground bounce and improve PSRR in noisy environments |
| 11 VOCM | Output common-mode voltage | Provides common-mode level for differential ADC interface; matches VCMHI within ±1.6 mV |
| 12 VOUT | Analog output | Buffered pH signal output (INP − VCM) after PGA amplification; drives 1 MΩ load |
Key Features
| Feature | Design Value |
|---|---|
| Active guarding architecture | Dual GUARD1/GUARD2 outputs eliminate need for external op-amps in guard-ring layout |
| pH buffer input bias current | ±125 fA (25°C) - reduces voltage error to sub-microvolt level with 1 GΩ electrode impedance |
| VCM/VCMHI dual-buffering | Separate buffered (VCM) and high-Z (VCMHI) common-mode outputs enable flexible ADC interfacing |
| Zero-power electrode protection | <600 fA input bias current with VS = 0 V - prevents pH probe degradation during power-off state |
| Integrated 5× PGA | Fixed-gain amplifier with ±275 µV offset and 80 dB CMRR - simplifies signal chain for 16-bit ADCs |
Applications
| Portable pH Meters | Industrial Process Analyzers |
|---|---|
|
Use Scenario: Handheld water quality testers used by field technicians for real-time pH verification in wastewater streams and aquaculture tanks. IC Role / Device Role / Timing Role: Front-end signal conditioner converting high-impedance pH electrode output into low-impedance, noise-immune analog signal for MCU-integrated ADC. Use Value: Enables >12-month battery life via 50 µA operating current and eliminates drift-induced recalibration due to ultra-low input bias current. |
Use Scenario: Continuous pH monitoring in chemical reactor vessels where temperature swings exceed 100°C and EMI is severe. IC Role / Device Role / Timing Role: Precision AFE providing stable common-mode referencing (VCM/VOCM) and active guarding against parasitic leakage in long cable runs. Use Value: Maintains ±0.01 pH accuracy across –40°C to +125°C via <±2.5 µV/°C offset drift and 80 dB PSRR at DC. |
| Lab-on-a-Chip Sensors | Environmental Monitoring Stations |
|
Use Scenario: Microfluidic cartridge-based analyzers requiring miniaturized, low-power pH detection for point-of-care diagnostics. IC Role / Device Role / Timing Role: Single-chip AFE integrating pH buffer, VCM generation, and PGA - replacing 3+ discrete op-amps and passive components. Use Value: Reduces BOM count by 70% and PCB area by 40% versus discrete solutions while guaranteeing sub-fA input performance. |
Use Scenario: Solar-powered remote stations measuring pH in rivers and lakes over multi-year deployments with no maintenance access. IC Role / Device Role / Timing Role: Low-quiescent-current AFE supporting intermittent wake-up sampling to extend battery life beyond 5 years. Use Value: Achieves 50 µA active current and <1 nA shutdown leakage - enabling energy harvesting compatibility and long-term stability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar pH-sensing AFE applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD8603ARZ | Single precision op-amp (IB = 1 pA typ), no integrated guarding or VCM generation | Requires external guard driver, VCM buffer, and PGA - increases layout complexity and leakage risk | Choose only when full custom AFE design is needed and board space allows discrete implementation |
| LMP91000MT/NOPB | Higher-power AFE (120 µA), wider supply (2.7–5.5 V), no GUARD pins, supports 3-electrode sensors | Designed for amperometric gas sensors; lacks pH-specific low-bias optimization and zero-voltage protection | Select for electrochemical sensors other than pH; avoid for pH due to 10× higher input bias current |
Compared with AD8603ARZ and LMP91000MT/NOPB, the LMP91200MT/NOPB uniquely delivers integrated active guarding, sub-fA input bias, and zero-supply electrode protection - making it the only single-chip solution qualified for high-accuracy, battery-operated pH measurement without external support circuitry.
Availability
LMP91200MT/NOPB is available at Aetrix Electronics and suitable for portable pH meters, industrial process analyzers, lab-on-a-chip diagnostic devices, and solar-powered environmental monitoring stations requiring stable component supply and long-lifecycle assurance.
Supply support for LMP91200MT/NOPB 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 headquartered in Dallas, Texas, specializing in analog and embedded processing technologies with over 50 years of precision signal-chain innovation.
The LMP91200MT/NOPB belongs to TI's Sensor AFE product line, engineered specifically for low-power, high-impedance electrochemical sensing - targeting pH, ORP, and ion-selective electrode applications in portable and industrial instrumentation.
FAQ
What is the maximum electrode impedance supported by the LMP91200MT/NOPB?
The LMP91200MT/NOPB supports pH electrodes with output impedances up to 1 GΩ while maintaining measurement accuracy. Its ±125 fA input bias current (25°C) limits voltage error to ≤125 µV even at 1 GΩ source impedance - well within the 1 mV error budget required for 0.02 pH unit resolution using the Nernst equation.
Does the LMP91200MT/NOPB require external components for active guarding?
No, the LMP91200MT/NOPB does not require external components for active guarding. It provides two dedicated guard outputs (GUARD1 and GUARD2) that track the INP pin voltage, enabling direct connection to PCB guard rings or triaxial cable shields without additional op-amps or passive networks.
How does the LMP91200MT/NOPB protect pH electrodes when unpowered?
When VDD = 0 V, the LMP91200MT/NOPB maintains an input bias current of ±600 fA (25°C) at INP - reducing electrochemical degradation of pH glass membranes during storage or standby. This zero-supply protection is intrinsic to its input stage design and requires no external circuitry.
Can the LMP91200MT/NOPB be used with differential ADCs?
Yes, the LMP91200MT/NOPB supports differential ADC interfacing via its VOCM pin, which provides a precise common-mode voltage matched to VCMHI within ±1.6 mV. Combined with VOUT, this enables true differential acquisition without external level-shifting or resistor networks.
What is the gain configuration of the PGA in the LMP91200MT/NOPB?
The PGA in the LMP91200MT/NOPB has a fixed gain of 5 V/V and is not user-programmable. It is optimized for scaling the ±415 mV pH electrode output to a ±2.075 V range compatible with standard 12–16 bit SAR ADCs, with gain accuracy of ±1.3% over temperature.
LMP91200MT/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Series:
- -
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Supply:
- 50 µA
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
LMP91200MT/NOPB FAQ
1.How can I place an order for LMP91200MT/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LMP91200MT/NOPB 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 LMP91200MT/NOPB reliable?
The price and inventory of LMP91200MT/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LMP91200MT/NOPB is usually 5 days.
3.What payment methods are accepted for LMP91200MT/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LMP91200MT/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LMP91200MT/NOPB?
LMP91200MT/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LMP91200MT/NOPB 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 LMP91200MT/NOPB?
For technical support, including LMP91200MT/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LMP91200MT/NOPB requirements.
6.How does Aetrix verify that LMP91200MT/NOPB is sourced from the original manufacturer or authorized distributors?
All LMP91200MT/NOPB 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 LMP91200MT/NOPB meets industry standards.
7.What is the process for return or replacement of LMP91200MT/NOPB?
All LMP91200MT/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LMP91200MT/NOPB, 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 LMP91200MT/NOPB part is unused and in its original packaging.
Return procedure for LMP91200MT/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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