LMP91200 Configurable AFE for Low-Power Chemical Sensing Applications General Description Key Specifications The LMP91200 is a configurable sensor AFE for use in low power analytical sensing applications. The LMP91200 is designed for 2-electrode sensors. This device provides all of the functionality needed to detect changes based on a delta voltage at the sensor. Optimized for low-power applications, the LMP91200 works over a voltage range of 1.8V to 5.5V. With its extremely low input bias current it is optimized for use with pH sensors. Also in absence of supply voltage the very low input bias current reduces degradation of the pH probe when connected to the LMP91200. The Common Mode Output pin (VOCM) provides a common mode offset, which can be programmed to different values to accommodate pH sensor output ranges. For applications requiring a high impedance common mode this option is also available. Two guard pins provide support for high parasitic impedance wiring. Support for an external Pt1000, Pt100, or similar temperature sensor is integrated in the LMP91200. The control of this feature is available through the SPI interface. Additionally, a user controlled sensor diagnostic test is available. This function tests the sensor for proper connection and functionality. Depending on the configuration, total current consumption for the device is 50µA while measuring pH. Available in a 16-pin TSSOP package, the LMP91200 operates from -40°C to +125°C. Unless otherwise noted, typical values at TA = 25°C, VS=(VDD-GND) = 3.3V. ■ pH Buffer Input bias current (0<VINP <3.3V) ±125 fA — max @ 25°C ±445 fA — max @ 85°C ■ pH Buffer Input bias current (-500mV<VINP-VCM <500mV), VS=(VDD-GND)=0V ±600 fA — max @ 25°C ±6.5 pA — max @ 85°C ±200 µV ■ pH Buffer Input offset voltage ±2.5 μV/°C ■ pH Buffer Input offset voltage drift 50 μA ■ Supply current (pH mode) 1.8 V to 5.5 V ■ Supply voltage -40°C to 125°C ■ Operating temperature range 16-Pin TSSOP ■ Package Features ■ Programmable output current in temperature measure■ ■ ■ ■ ■ ment Programmable Output common mode voltage Active guarding On board sensor test Supported by Webench Sensor AFE Designer Supported by Webench Sensor Designer Tools Applications ■ pH sensor platforms Typical Application 30165507 WEBENCH® is a Registered trademark of Texas Instruments Incorporated. LMP™ is a trademark of Texas Instruments Incorporated. © 2012 Texas Instruments Incorporated 301655 SNAS571B www.ti.com LMP91200 Configurable AFE for Low-Power Chemical Sensing Applications June 25, 2012 LMP91200 Ordering Information Package 16-Pin TSSOP Part Number Package Marking LMP91200MT LMP91200MTX LMP91200MT Transport Media 95 Units/Rail 2.5k Units Tape and Reel NSC Drawing MTC16 Connection Diagram 16-Pin TSSOP 30165503 Top View Pin Descriptions Pin Name Description 1 VDD Positive Power Supply 2 CAL Connect an external precision resistor here for purpose of temperature measurement calibration 3 RTD Pt100/Pt1000 input / internal current source output 4 GUARD1 Active guard pin 5 INP Non-inverting analog input of pH buffer 6 GUARD2 Active guard pin 7 VCMHI High Impedance Programmable Common Mode output 8 VCM Buffered Programmable Common Mode output 9 VREF Voltage reference input 10 GND Analog ground 11 VOCM Output common mode voltage 12 VOUT Analog Output 13 SDO_DIAG Serial Data Out /Diagnostic enable 14 CSB Chip select, low active. 15 SCLK Serial Clock 16 SDI Serial Data In www.ti.com 2 If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 2) Human Body Model Machine Model Charge Device Model Supply Voltage (VS = VDD-GND) Voltage between any two pins Current out at any pin 2000V 150V 1000V -0.3V to 6.0V -0.3V to VDD+0.3V 5mA Electrical Characteristics Operating Ratings -65°C to 150°C +150°C (Note 1) Supply Voltage (VS=VDD-GND) Temperature Range 1.8V to 5.5V -40°C to 125°C Package Thermal Resistance (θJA(Note 3)) 16-Pin TSSOP 31°C/W (Note 4) Unless otherwise specified, all limits guaranteed for TA = 25°C. VS=(VDD-GND)=3.3V. VREF=3.3V. Boldface limits apply at the temperature extremes. Symbol Parameter Typ (Note 5) Max (Note 6) pH measurement mode 50 54 59 Temperature measurement mode, ICS=100uA 300 325 330 Temperature measurement mode, ICS=200uA 400 432 437 Temperature measurement mode, ICS=1000uA 350 364 372 Temperature measurement mode, ICS=2000uA 470 477 477 Condition Min (Note 6) Units Power supply Is Supply Current (Note 7, Note 16) µA pH Buffer AolpH VospH Open loop Gain Input Voltage Offset (Note 7) TcVospH Input offset voltage drift (Note 8, Note 14) VOSpH_drift Long term VOSpH drift (Note 9) IbpH GBWPpH CMRRpH Input bias current at INP (Note 14) Gain Bandwidth Product (Note 14) INP=1.65V 300mV=VOUT=VDD-300mV; 90 120 dB INP=1/8VREF -200 -350 200 350 INP=7/8VREF -200 -350 200 350 INP=1/8VREF -2.5 2.5 INP=7/8VREF -2.5 2.5 500 hours OPL 150 µV uV/°C µV 0V<INP<3.3V -125 125 0V<INP<3.3V, 85°C -445 445 fA 0V<INP<3.3V, 125°C -1.5 1.5 pA -500mV<(INP-VCM)<500mV, VS=0V. -600 600 fA -500mV<(INP-VCM)<500mV, 85°C, VS=0V. -6.5 6.5 pA -500mV<(INP-VCM)<500mV, 125°C, VS=0V. -100 100 pA CL=10pF, RL=1Mohm DC_Common mode rejection 1/8VREF<INP<7/8VREF ratio 3 220 80 fA KHz dB www.ti.com LMP91200 Storage Temperature Range Junction Temperature (Note 3) For soldering specifications: see product folder at www.ti.com and www.ti.com/lit/an/snoa549c/snoa549c.pdf Absolute Maximum Ratings (Note 1) LMP91200 Symbol PSRRpH Parameter Condition DC_Power supply rejection ratio En_RMSpH Input referred frequency) (Note 14) noise enpH Input referred noise (high frequency) (Note 14) IscpH Output short circuit current (Note 19) Min (Note 6) 1.8V<VDD<5V INP=1/8VREF 80 1.8V<VDD<5V INP=7/8VREF 80 Typ (Note 5) Max (Note 6) Units dB (low Integrated 0.1Hz to 10Hz 2.6 f=1kHz 90 µVPP nV/ Sourcing, Vout to GND INP=1.65V 10 13 mA Sinking, Vout to VDD INP=1.65V 8 12 mA VCM Buffer VCMHI_acc VCMHI accuracy Tc_VCMHI VCMHI temperature coefficient (Note 10, Note 14) -1.6 -40°C<TA<125°C -18 VCMHI_acc_ VREF VCMHI_acc vs. VREF (Note 11, Note 14) 1.8V<VREF<5.0V -500 RoutVCMHI VCMHI Output Impedance (Note 14) VCMHI=1/2 VREF AolVCM Open loop Gain (Note 7) VCMHI=1/2 VREF, 300mV<VCM<VDD-300mV; VosVCM (VCM-VCMHI) (Note 7) enVCM Input referred noise (high frequency) (Note 14) IscVCM Output short circuit current (Note 19) -100 300 µV/V 250 KΩ 120 dB -200 -350 200 350 -2.5 2.5 -2.5 2.5 f=1KHz noise µV/°C VCMHI=7/8 VREF Output Impedance (Note 14) Input referred frequency) (Note 14) 8 200 350 ZoutVCM En_RMSVCM -5 -200 -350 Input offset voltage drif ot (VCM- VCMHI=1/8 VREF VCMHI) VCMHI=7/8 VREF (Note 8, Note 14) DC_Power supply rejection ratio mV VCMHI=1/8 VREF TcVosVCM PSRRVCM 90 1.6 4 1.8V<VDD<5V, VCMHI=1/8VREF 80 1.8V<VDD<5V, VCMHI=7/8VREF 80 µV µV/°C Ω dB (low Integrated 0.1Hz to 10Hz 2.6 f=1KHz 90 Sourcing, Vout to GND VCMHI=1/2VREF 10 16 Sinking, Vout to VDD VCMHI=1/2VREF 8 12 µVPP nV/ mA Current Source ICS www.ti.com Current Source ICAL, IRTD Programmable current 4 100 200 1000 2000 µA Parameter noise Min (Note 6) Condition Typ (Note 5) Max (Note 6) Units In_RMSCS Input referred frequency) (Note 14) (low inCS Input referred noise (high frequency) (Note 14) TcICS Current Source drift(Note 12) (Note 14) -200 ±35 200 ppm/°C I_accCS Current Source accuracy -2.5 1 2.5 % Integrated 0.1Hz to 10Hz 33 f=1KHz 120 nAPP pA/ PGA VosPGA Input Voltage Offset (Note 7) +IN_PGA (Internal node) = 500mV -275 -480 275 480 µV TcVosPGA Input offset voltage drift (Note 8, Note 14) +IN_PGA (Internal node) = 500mV -2.5 2.5 uV/°C AolPGA Open loop Gain +IN_PGA (Internal node) = 500mV 90 AvPGA Gain Av_accPGA Gain accuracy En_RMSPGA Input referred frequency) (Note 14) enPGA Programmable gain 120 dB 5 10 V/V -1.3 noise 1.3 % (low Integrated 0.1Hz to 10Hz 2.6 Input referred noise (high frequency) (Note 14) f=1KHz 90 PSRRPGA DC_Power supply rejection ratio 1.8V<VDD<5V, +IN_PGA (Internal node) = 500mV 80 Sourcing, Vout to GND +IN_PGA (Internal node) = 500mV 10 16 IscPGA Output short circuit current (Note 19) Sinking, Vout to VDD +IN_PGA (Internal node) = 500mV 8 12 µVPP nV/ dB mA Reference Input RinVREF Input impedance (Note 14) 500 Electrical Characteristics (Serial Interface) KΩ (Note 4) Unless otherwise specified. All limits guaranteed for TA=25°C, VS=(VDD-GND)=3.3V. Symbol Parameter VIL Logic Low Threshold VIH Logic High Threshold (SDO pin) VOL Output Logic LOW Threshold (SDO pin) VOH Output Logic High Threshold t1 t2 Condition Min (Note 6) Typ (Note 5) Max (Note 6) Units 0.3XVDD V 0.7XVDD V ISDO=100µA 0.2 ISDO=2mA 0.4 V ISDO=100µA VDD-0.2 ISDO=2mA VDD-04 High Period, SCLK (Note 15) 100 ns Low Period, SCLK (Note 15) 100 ns t3 Set Up Time, CSB to SCLK (Note 15) 50 ns t4 Set Up Time, SDI to SCLK (Note 15) 30 ns t5 Hold Time,S CLK to SDI (Note 15) 10 ns t6 Hold Time,SCLK to SDO_DIAG (Note 15) 40 ns 5 V www.ti.com LMP91200 Symbol LMP91200 Symbol Parameter Condition Min (Note 6) t7 Hold Time, SCLK Transition to CSB Rising Edge (Note 15) 50 ns t8 CSB Inactive (Note 15) 50 ns t9 Hold Time, SCLK Transition to CSB Falling Edge (Note 15) 10 ns tR/tF SDO_DIAG Signal Rise and Fall Times Diagnostic disabled (Note 14, Note 15) Electrical Characteristics (Diagnostic) Typ (Note 5) Max (Note 6) 30 Units ns (Note 4) Unless otherwise specified. All limits guaranteed for TA=25°C, VS=(VDD-GND)=3.3V. Symbol Parameter Condition Min (Note 6) Typ (Note 5) Max (Note 6) Units SDO_DIAG setup time (Note 14) 200 ns DIAG_tR/ DIAG_tF Diagnostic Rise and Fall Times (Signal at SDO_DIAG pin, in Diagnostic Mode) (Note 14) 30 ns DIAG_tON Minimum tON of the diagnostic pulse at SDO_DIAG pin in Diagnostic Mode (Note 14) 100 ns Base pulse = VCM; High level pulse = VCM+5%VREF 165 mV Base pulse = VCM; High level pulse = VCM-5%VREF 165 mV 0.1 % DIAG_tSET Positve Diagnostic VCM_DIAGPOS amplitude (Note 14) pulse Negative Diagnostic pulse VCM_DIAGNEG amplitude (Note 14) VCM_DIAG_acc Diagnostics Pulse accuracy (Note 14) VCM_DIAGtR Diagnostics Pulse rise time (Note 14) 10% to 90% C=15pF 10 us VCM_DIAGtF Diagnostics Pulse fall time (Note 14) 90% to 10% C=15pF 10 us Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics Tables. Note 2: Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC) Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC). Note 3: The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly onto a PC Board. Note 4: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that TJ = TA. No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self-heating where TJ >TA. Note 5: Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material. Note 6: Limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlations using the Statistical Quality Control (SQC) method. Note 7: Boldface limits are production tested at 125°C. Limits are guaranteed through correlations using the Statistical Quality Control (SQC) method. Note 8: Offset voltage average drift is determined by dividing the change in VOS at the temperature extremes by the total temperature change. Note 9: Offset voltage long term drift is determined by dividing the change in VOS at time extremes of OPL procedure by the length of the OPL procedure. OPL procedure: 500 hours at 150°C are equivalent to about 15 years. Note 10: VCMHI voltage average drift is determined by dividing the change in VCMHI at the temperature extremes by the total temperature change. Note 11: VCMHI_acc vs. VREF is determined by dividing the change in VCMHI_acc at the VREF extremes by the total VREF change. Note 12: Current source drift is determined by dividing the change in ICS at the temperature extremes by the total temperature change. www.ti.com 6 LMP91200 Note 13: Positive current corresponds to current flowing into the device. Note 14: This parameter is guaranteed by design and/or characterization and is not tested in production. Note 15: Load for these tests is shown in the timing diagram test circuit. Note 16: Excluding all currents which flows out from the device. Note 17: The short circuit test is a momentary open loop test. Note 18: The voltage on any pin should not exceed 6V relative to any other pins. Note 19: Short circuit test is a momentary test. Test Circuit Diagrams 30165504 FIGURE 1. 30165505 FIGURE 2. SERIAL INTERFACE TIMING DIAGRAM 7 www.ti.com LMP91200 30165506 FIGURE 3. DIAGNOSTIC TIMING DIAGRAM www.ti.com 8 Unless otherwise specified, TA=25°C, VS=(VDD-GND)=3.3V, pH Buffer Input Bias Current vs. VINP - Device ON 100 80 500 Average Average -3σ Average +3σ 400 300 40 INPUT BIAS (fA) INPUT BIAS (fA) 60 pH Buffer Input Bias Current vs. VINP - Device OFF 20 0 -20 -40 -60 200 100 0 -100 -200 -300 -80 -400 TA=25°C -100 0.0 Average Average -3σ Average +3σ 0.5 1.0 1.5 2.0 INP (V) 2.5 3.0 TA=25°C -500 3.5 -0.50 -0.25 0.00 0.25 INP-VCM (V) 30165510 30165511 pH Buffer Input Bias Current vs. VINP - Device ON 300 240 pH Buffer Input Bias Current vs. VINP - Device OFF 5 Average Average -3σ Average +3σ 4 3 120 INPUT BIAS (pA) INPUT BIAS (fA) 180 60 0 -60 -120 -180 Average Average -3σ Average +3σ 2 1 0 -1 -2 -3 -240 -4 TA=85°C -300 0.0 0.5 1.0 1.5 2.0 INP (V) 2.5 3.0 TA=85°C -5 3.5 -0.50 -0.25 0.00 0.25 INP-VCM (V) 30165563 800 pH Buffer Input Bias Current vs. VINP - Device OFF 80 Average Average -3σ Average +3σ 60 400 INPUT BIAS (pA) INPUT BIAS (fA) 600 200 0 -200 -400 -600 -800 0.0 0.5 1.0 1.5 2.0 INP (V) 2.5 3.0 Average Average -3σ Average +3σ 40 20 0 -20 -40 -60 TA=125°C -1000 0.50 30165565 pH Buffer Input Bias Current vs. VINP - Device ON 1000 0.50 TA=125°C -80 3.5 -0.50 30165564 -0.25 0.00 0.25 INP-VCM (V) 0.50 30165566 9 www.ti.com LMP91200 Typical Performance Characteristics VREF=3.3V. 500 400 pH Buffer Input Bias Current vs. Temp - Device OFF 5 Average Average -3σ Average +3σ 3 200 100 0 -100 -200 -300 -400 -500 25 Average Average -3σ Average +3σ 4 INPUT BIAS (pA) INPUT BIAS (fA) 300 2 1 INP-VCM = 100mV 0 -1 INP-VCM = -100mV -2 -3 -4 INP=1.65V -5 45 65 85 105 TEMPERATURE (°C) 125 25 50 75 100 TEMPERATURE (°C) 30165512 pH Buffer Input Voltage Offset 18 18 UNITS TESTED >5000 INP=1/8VREF 15 PERCENTAGE (%) PERCENTAGE (%) 15 12 9 6 9 6 3 0 0 -200 -150 -100 -50 0 50 100 150 200 VOSPH (μV) UNITS TESTED >5000 INP=7/8VREF 12 3 -200 -150 -100 -50 0 50 100 150 200 VOSPH (μV) 30165540 30165541 pH Buffer TcVos 35 30 pH Buffer TcVos 35 UNITS UNITS TESTED TESTED >5000 >5000 INP=1/8VREF INP=1/8VREF 30 PERCENTAGE (%) 25 20 15 10 UNITS UNITS TESTED TESTED >5000 >5000 INP=1/8VREF INP=7/8VREF 25 20 15 10 5 5 0 0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 TCVOSPH (μV/°C) -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 TCVOSPH (μV/°C) 30165549 www.ti.com 125 30165513 pH Buffer Input Voltage Offset PERCENTAGE (%) LMP91200 pH Buffer Input Bias Current vs. Temp - Device ON 30165550 10 100 pH Buffer DC PSRR vs. Temperature 110 VDD=1.8V VDD=3.3V VDD=5V INP=7/8 VREF INP=1/8VREF 105 PSRR (dB) 105 95 90 100 95 85 80 90 -50 -25 0 25 50 75 100 125 -50 -25 0 25 50 75 TEMPERATURE (°C) 100 125 30165514 30165515 pH Buffer Time domain Voltage Noise pH Buffer Input Offset Voltage Drift 125 INP=7/8VREF INP=1/8VREF INTEGRATED NOISE (500nV/DIV) 100 VOSPH (μV) 75 50 25 0 -25 -50 -75 -100 -125 1 TIME (1s/DIV) 10 100 OPL TIME (h) 1k 30165517 30165567 pH Buffer CMRR vs. VINP - lower rail pH Buffer CMRR vs. VINP - upper rail 100 120 VDD=VREF=3.3V 90 110 80 100 CMRR (dB) CMRR (dB) LMP91200 pH Buffer DC CMRR vs. Temperature 70 60 90 80 50 70 40 60 0.00 0.08 0.16 0.24 INP (V) 0.32 0.40 2.9 30165571 VDD=VREF=3.3V 3.0 3.1 INP (V) 3.2 3.3 30165574 11 www.ti.com LMP91200 pH Buffer CMRR vs. VINP - lower rail pH Buffer CMRR vs. VINP - upper rail 120 120 VDD=VREF=5V VDD=VREF=5V 110 CMRR (dB) CMRR (dB) 110 100 100 90 80 90 70 80 60 0.00 0.12 0.24 0.36 INP (V) 0.48 0.60 4.4 4.5 4.6 4.7 4.8 INP (V) 4.9 30165572 30165573 pH Buffer CMRR vs. Frequency pH Buffer PSRR vs. Frequency 90 90 70 80 PSRR (dB) CMRR (dB) INP=1.65V 80 85 75 70 60 50 40 30 20 65 10 60 0 10 100 1k 10k FREQUENCY (Hz) 100k 10 100 1k FREQUENCY (Hz) 30165519 VCM Buffer Input Voltage Offset 18 UNITS TESTED >5000 VCMHI=1/8VREF 15 PERCENTAGE (%) PERCENTAGE (%) 12 9 6 3 UNITS TESTED >5000 VCMHI=7/8VREF 12 9 6 3 0 0 -200 -150 -100 -50 0 50 100 150 200 VOSVCM (μV) -200 -150 -100 -50 0 50 100 150 200 VOSVCM (μV) 30165542 www.ti.com 10k 30165520 VCM Buffer Input Voltage Offset 15 5.0 30165543 12 VCM Buffer TcVos 35 40 UNITS TESTED >5000 VCMHI=1/8VREF UNITS TESTED >5000 VCMHI=7/8VREF 30 30 PERCENTAGE (%) PERCENTAGE (%) 35 25 20 15 10 25 20 15 10 5 5 0 0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 TCVOSVCM (μV/°C) -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 TCVOSVCM (μV/°C) 30165551 30165552 VCM Buffer DC CMRR vs. Temperature 105 VCM Buffer DC PSRR vs. Temperature 110 VDD=1.8V VDD=3.3V VDD=5V VCMHI=7/8 VREF VCMHI=1/8VREF 105 PSRR (dB) CMRR (dB) 100 95 90 100 95 85 -50 LMP91200 VCM Buffer TcVos 90 -25 0 25 50 75 TEMPERATURE (°C) 100 125 -50 -25 0 25 50 75 TEMPERATURE (°C) 100 125 30165521 30165522 VCM Buffer Time domain Voltage Noise VCM Buffer PSRR vs. Frequency 90 VCMHI=1.65V INTEGRATED NOISE (500nV/DIV) 80 PSRR (dB) 70 60 50 40 30 20 10 10 TIME (1s/DIV) 30165526 100 1k FREQUENCY (Hz) 10k 30165529 13 www.ti.com LMP91200 VCMHI error vs. Temp 0.30 0.30 VCMHI=1/8VREF VCMHI=1/4VREF VCMHI=3/8VREF VCMHI=1/2VREF VCMHI=5/8VREF VCMHI=3/4VREF VCMHI=7/8VREF 0.20 0.15 0.20 0.10 0.05 0.15 0.10 0.05 0.00 0.00 -0.05 -0.05 -0.10 -0.10 -50 -25 VCMHI=1/8VREF VCMHI=1/4VREF VCMHI=3/8VREF VCMHI=1/2VREF VCMHI=5/8VREF VCMHI=3/4VREF VCMHI=7/8VREF 0.25 ERROR (%) 0.25 ERROR (%) VCMHI error vs. Supply Voltage 0 25 50 75 100 125 TEMPERATURE (°C) 1.8 2.2 2.6 3.0 3.4 3.8 4.2 4.6 5.0 SUPPLY VOLTAGE (V) 30165525 30165568 PGA Input Voltage Offset 15 30 UNITS TESTED >5000 +IN_PGA=500mV UNITS TESTED >5000 +IN_PGA=500mV 27 24 PERCENTAGE (%) 12 PERCENTAGE (%) PGA TcVos 9 6 3 21 18 15 12 9 6 3 0 0 -275-220-165-110 -55 0 55 110 165 220 275 VOSPGA (μV) -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 TCVOSPGA (μV/°C) 30165544 30165553 PGA DC PSRR vs. Temperature 105.0 PGA Gain error vs. Temp 0.10 +IN_PGA=500mV 0.08 0.06 GAIN ERROR (%) PSRR (dB) 102.5 100.0 97.5 95.0 0.02 0.00 -0.02 -0.04 -0.08 90.0 -25 -0.10 -50 0 25 50 75 100 125 TEMPERATURE (°C) 30165560 www.ti.com 0.04 -0.06 92.5 -50 PGA Gain = 5V/V PGA Gain = 10V/V -25 0 25 50 75 100 125 TEMPERATURE (°C) 30165531 14 LMP91200 PGA Time domain Voltage Noise PGA PSRR vs. Frequency 90 INTEGRATED NOISE (500nV/DIV) 80 +INPGA=100mV PSRR (dB) 70 60 50 40 30 20 10 0 10 TIME (1s/DIV) 100 1k FREQUENCY (Hz) 10k 30165532 30165534 Current Source (ICS=100µA) Temperature coefficient Current Source (ICS=100µA) 30 30 UNITS TESTED >5000 IOUTCS=100μA 25 PERCENTAGE (%) PERCENTAGE (%) 25 20 15 10 5 UNITS TESTED >5000 IOUTCS=100μA 20 15 10 5 0 0 98 99 100 IOUTCS (μA) 101 102 -200 -150 -100 -50 0 50 100 150 200 IOUTCS (ppm/°C) 30165545 30165554 Current Source (ICS=200µA) PERCENTAGE (%) 25 30 UNITS TESTED >5000 IOUTCS=200μA 25 PERCENTAGE (%) 30 Temperature coefficient Current Source (ICS=200µA) 20 15 10 20 15 10 5 5 0 0 196 197 198 199 200 201 202 203 204 IOUTCS (μA) UNITS TESTED >5000 IOUTCS=200μA -200 -150 -100 -50 0 50 100 150 200 IOUTCS (ppm/°C) 30165546 30165555 15 www.ti.com LMP91200 Current Source (ICS=1000µA) Temperature coefficient Current Source (ICS=1000µA) 25 25 UNITS TESTED >5000 IOUTCS=1000μA 20 PERCENTAGE (%) PERCENTAGE (%) 20 15 10 5 UNITS TESTED >5000 IOUTCS=1000μA 15 10 5 0 0 980 990 1000 1010 IOUTCS (μA) 1020 -200 -150 -100 -50 0 50 100 150 200 IOUTCS (ppm/°C) 30165547 30165556 Current Source (ICS=2000µA) 25 30 UNITS TESTED >5000 IOUTCS=2000μA 25 PERCENTAGE (%) 20 PERCENTAGE (%) Temperature coefficient Current Source (ICS=2000µA) 15 10 5 UNITS TESTED >5000 IOUTCS=2000μA 20 15 10 5 0 0 1960 1980 2000 2020 IOUTCS (μA) 2040 -200 -150 -100 -50 0 50 100 150 200 IOUTCS (ppm/°C) 30165548 30165557 Supply current vs. digital input voltage 1.0 1000 0.8 900 0.6 800 EXTRA CURRENT (μA) ERROR (%) Current Source accuracy (I_accCS) vs. Supply Voltage 0.4 0.2 0.0 -0.2 -0.4 -0.6 700 600 500 400 300 200 -0.8 100 -1.0 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 DIGITAL PIN VOLTAGE (V) 1.8 2.2 2.6 3.0 3.4 3.8 4.2 4.6 5.0 SUPPLY VOLTAGE (V) 30165537 30165536 www.ti.com VDD=5V 16 50 LMP91200 Supply current (pH Mode) vs. Temperature Supply current (Temp Mode) vs. Temperature 450 pH Mode SUPPLY CURRENT (μA) SUPPLY CURRENT (μA) 430 45 40 35 410 390 370 350 Temp Mode, IOUTCS=100uA Temp Mode, IOUTCS=200uA Temp Mode, IOUTCS=1mA Temp Mode, IOUTCS=2mA 330 310 30 -50 -25 0 25 50 75 TEMPERATURE (°C) 290 -50 100 125 -25 0 25 50 75 TEMPERATURE (°C) 100 125 30165561 30165538 Supply current (pH Mode) vs. Supply Voltage 450 pH Mode SUPPLY CURRENT (μA) SUPPLY CURRENT (μA) 50 Supply current (Temp Mode) vs. Supply Voltage 45 40 35 30 1.5 420 390 360 330 Temp Mode, IOUTCS=100uA Temp Mode, IOUTCS=200uA Temp Mode, IOUTCS=1mA Temp Mode, IOUTCS=2mA 300 270 2.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 1.5 30165562 2.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 30165539 17 www.ti.com LMP91200 pH the Output signal can be referred either to VCM or GND. When measuring temperature the Output signal is referred to GND. The Output configuration is controlled through the SPI interface. Functional Description GENERAL INFORMATION The LMP91200 is a configurable sensor AFE for use in low power analytical sensing applications. The LMP91200 is designed for 2-electrode sensors. This device provides all of the functionality needed to detect changes based on a delta voltage at the sensor. Optimized for low-power applications, the LMP91200 works over a voltage range of 1.8V to 5.5V. With its extremely low input bias current it is optimized for use with pH sensors. Also in absence of supply voltage the very low input bias current reduces degradation of the pH probe when connected to the LMP91200. The Common Mode Output pin (VOCM) provides a common mode offset, which can be programmed to different values to accommodate pH sensor output ranges. For applications requiring a high impedance common mode this option is also available. Two guard pins provide support for high parasitic impedance wiring. Support for an external Pt1000, Pt100, or similar temperature sensor is integrated in the LMP91200. The control of this feature is available through the SPI interface. Additionally, a user controlled sensor diagnostic test is available. This function tests the sensor for proper connection and functionality. SERIAL CONTROL INTERFACE OPERATION All the features of the LMP91200 (Mode of Operation, PGA Gain, Voltage reference, Diagnostic) are by data stored in a programming register. Data to be written into the control register is first loaded into the LMP91200 via the serial interface. The serial interface employs a 16-bit shift register. Data is loaded through the serial data input, SDI. Data passing through the shift register is output through the serial data output, SDO_DIAG. The serial clock, SCK controls the serial loading process. All sixteen data bits are required to correctly program the LMP91200. The falling edge of CSB enables the shift register to receive data. The SCK signal must be high during the falling and rising edge of CSB. Each data bit is clocked into the shift register on the rising edge of SCLK. Data is transferred from the shift register to the holding register on the rising edge of CSB. Configuration Register Bit pH Buffer The pH Buffer is a unity gain buffer with a input bias current in the range of tens fA at room. Its very low bias current introduces a negligible error in the measurement of the pH. The ph buffer is provided with 2 guard pins (GUARD1, GUARD2) in order to minimize the leakage of the input current and to make easy the design of a guard ring. Common mode selector and VCM buffer The common mode selector allows to set 7 different values of common mode voltage (from 1/8 VREF to 7/8VREF with 1/8 VREF step) according to the applied voltage reference at VREF pin. Both buffered and unbuffered version of the set common mode voltage are available respectively at VCM pin and VCMHI pin. A copy of the buffered version is present at VOCM pin in case of differential measurement. Current Source and PGA The internal current source is programmable current generator which is able to source 4 different current values (100µA, 200µA, 1mA, 2mA) in order to well stimulate Pt100 and Pt1000 thermal resistor. The selected current is sourced from either RTD pin (pin for thermal resistor connection) or CAL pin (pin for reference resistor connection). The voltage across either the thermal resistor or the reference resistor is amplified by the PGA (5V/V, 10V/V) and provided at the VOUT pin when the LMP91200 is set in Temperature measurement mode. Output Muxes The output of the LMP91200 can be configured to support both differential and single ended ADC’s. When measuring www.ti.com 18 Name Description D15 MEAS_MO DE 0 1 pH measurement (default) Temp measurement D14 I_MUX 0 1 RTD (default) CAL [D13:D12] I_VALUE 00 01 10 11 D11 0 1 PGA 100µA (default) 200 µA 1 mA 2 mA 5 V/V (default) 10 V/V [D10 :D8] VCM 011 010 001 000 100 101 110 111 7/8Vref 3/4Vref 5/8Vref 1/2Vref (default) 1/2Vref 3/8Vref 1/4Vref 1/8 Vref D7 VOCM 0 1 VOCM (default) GND D6 DIAG_EN 0 1 DIAG pin disabled (default) DIAG pin enabled [D5 :D0] RESERVED RESERVED surement mode and collect both temperature and potential of sensing electrode. Theory of pH measurement pH electrode measurements are made by comparing the readings in a sample with the readings in standards whose pH has been defined (buffers). When a pH sensing electrode comes in contact with a sample, a potential develops across the sensing membrane surface and that membrane potential varies with pH. A reference electrode provides a second, unvarying potential to quantitatively compare the changes of the sensing membrane potential. Nowadays pH electrodes are composed of a sensing electrode with the reference electrode built into the same electrode body, they are called combination electrodes. A high input impedance meter serves as the readout device and calculates the difference between the reference electrode and sensing electrode potentials in millivolts. The millivolts are then converted to pH units according to the Nernst equation. Electrode behavior is described by the Nernst equation: E = Eo + (2.3 RT/nF) log aH+, where E is the measured potential from the sensing electrode, Eo is related to the potential of the reference electrode, (2.3 RT/nF) is the Nernst factor, log aH+ is the pH, (aH+ = activity of Hydrogen ions). 2.3 RT/nF, includes the Gas Law constant (R), Faraday’s constant (F), the temperature in degrees Kelvin (T) and the stoichiometric number of ions involved in the process (n). For pH, where n = 1, the Nernst factor is 2.3 RT/F. Since R and F are constants, the factor and therefore electrode behavior is dependent on temperature. The Nernst Factor is equivalent to the electrode slope which is a measure of the electrode response to the ion being detected. When the temperature is 25 °C, the theoretical Nernst slope is 59.16 mV/pH unit. pH measurement The output of a pH electrode ranges from 415 mV to −415 mV as the pH changes from 0 to 14 at 25°C. The output impedance of a pH electrode is extremely high, ranging from 10 MΩ to 1000 MΩ. The low input bias current of the LMP91200 allows the voltage error produced by the input bias current and electrode resistance to be minimal. For example, the output impedance of the pH electrode used is 10 MΩ, if an op amp with 3 nA of Ibias is used, the error caused due to this amplifier’s input bias current and the source resistance of the pH electrode is 30 mV! This error can be greatly reduced to 1.25µV by using the LMP91200. The pH measurement with the LMP91200 is straightforward, the pH electrode needs to be connected between VCM pin and INP pin. The voltage at VCM pin represent the internal zero of the system, so the potential of the electrode (voltage at INP pin) will be refered to VCM voltage. The common mode voltage can be set to well fit the input dynamic range of an external ADC connected between VOUT and VOCM when the LMP91200 is configured with differential output. In Table 1 a typical configuration of the register of the LMP91200 with VCM set at 1/2 of VREF and differential output. TABLE 1. Bit Name MEAS_MODE 0 D14 I_MUX Leave these bits as they have been configured for the temperature measurement. [D13:D12] I_VALUE D11 LMP91200 in pH meter with ATC (Automatic Temperature Compensation) The most common cause of error in pH measurements is temperature. Temperature variations can influence pH for the following reasons: the electrode slope will change with variations in temperature; buffer and sample pH values will change with temperature. Measurement drift can occur when the internal elements of the pH and reference electrodes are reaching thermal equilibrium after a temperature change. When the pH electrode and temperature probe are placed into a sample that varies significantly in temperature, the measurements can drift because the temperature response of the pH electrode and temperature probe may not be similar and the sample may not have a uniform temperature, so the pH electrode and temperature probe are responding to different environments. The pH values of buffers and samples will change with variations in temperature because of their temperature dependent chemical equilibria. The pH electrode should be calibrated with buffers that have known pH values at different temperatures. Since pH meters are unable to correct sample pH values to a reference temperature, due to the unique pH versus temperature relationship of each sample, the calibration and measurements should be performed at the same temperature and sample pH values should be recorded with the sample temperature. The LMP91200 offers in one package all the features to build a pH meter with ATC. Through the SPI Interface is possible to switch from pH measurement mode to temperature mea- Description D15 PGA pH measurement [D10 :D8] VCM 000 D7 VOCM 0 VOCM 1/2 VREEF D6 DIAG_EN 0 DIAGNOSTIC disabled [D5 :D0] RESERVED RESERVED Configuration register: pH measurement Temperature measurement The LMP91200 supports temperature measurement with RTD like Pt100 and Pt1000. According to the RTD connected to the LMP91200 the right amount of exciting current can be programmed: 100µA for Pt1000 and 1mA for Pt100, resulting in a nominal voltage drop of 100mV for both RTD’s at 0°C. This voltage can be amplified, using an internal amplifier with a factor of 5 or 10 V/V. In case of high precision temperature measurement it is possible to connect an external high accuracy resistor and implement a calibration procedure. The exciting current sourced by the LMP91200 can be multiplexed either into the RTD or into the external precision resistor in order to implement a 2-step or 3-step temperature measurement. The multi step temperature measurements allows to remove uncertainty of the temperature signal path. 1-step measurement In the one step measurement the voltage across the RTD (Pt100, Pt1000) due to the exciting current is amplified and measured. The temperature can be calculated according to the following equation: Temp(°C) = (PtRES_calculated – PtRES_nominal)/ alpha 19 (1) www.ti.com LMP91200 Application Information LMP91200 where alpha is the thermal coefficient of the RTD (it depends on the selected Ptres); PtRES_nominal is the value of the Ptres at 0degC. I_true is the real current which alternatively flows in the external precison resistance RREF and in the RTD. PGA_GAIN is the selected gain of the PGA. (2) where VOUT_RREF is the amplified voltage across the RREF at VOUT pin (ground referred), when the LMP91200 is configured according to Table 3. Inserting Equation 5 and Equation 6 in Equation 4 the temperature is given by the following equation: PtRES_calculated = (VOUT_PtRES/I_Pt)/PGA_GAIN I_true=(VOUT_RREF)/(PGA_GAIN*RREF) where VOUT_PtRES is the amplified voltage across the RTD at VOUT pin (ground referred) when the LMP91200 is configured according to Table 2. I_Pt is the value of the selected exciting current according to the RTD; PGA_GAIN is the selected gain of the PGA. Inserting Equation 2 in Equation 1 the temperature is given by the following equation: Temp(°C) = Temp(°C) = ((VOUT_PtRES/I_Pt)/ PGA_GAIN – PtRES_nominal)/alpha Temp(°C) = ((VOUT_PtRES /VOUT_RREF)*RREF– PtRES_nominal) /alpha Name Bit (3) Description D15 MEAS_MODE 1 Temp measurement D14 I_MUX 0 RTD [D13:D12] I_VALUE 00 10 D11 1 PGA 100µA (Pt1000) 1 mA (Pt100) 10 V/V [D10 :D8] VCM Leave these bits as they have been configured for the pH measurement. D7 VOCM 1 GND D6 DIAG_EN 0 DIAGNOSTIC disabled [D5 :D0] RESERVED RESERVED Name Description D15 MEAS_MODE 1 Temp measurement D14 I_MUX 1 RCAL [D13:D12] I_VALUE 00 10 D11 1 PGA [D10 :D8] VCM D7 VOCM 1 GND D6 DIAG_EN 0 DIAGNOSTIC disabled [D5 :D0] RESERVED RESERVED Bit 2-step measurement This method requires 2 acquisitions and a precision resistor (RREF) connected between CAL and GND pin, (the RTD is always connected between RTD and GND pin). The first acquisitions measure the voltage across the precision resistor in the same condition (source current and PGA gain) of the next temperature measurement in order to remove the uncertainty on the current source value. The second acquisition measures the voltage across the RTD (similar to the 1-step measure), in this case the formula to calculate the temperature is a little bit more complicate in order to take in account the non-ideality of the system (source current error). Name Description D15 MEAS_MODE 1 Temp measurement D14 I_MUX 0 RTD [D13:D12] I_VALUE 00 10 D11 1 PGA 100µA (Pt1000) 1 mA (Pt100) 10 V/V [D10 :D8] VCM Leave these bits as they have been configured for the pH measurement. D7 VOCM 1 GND D6 DIAG_EN 0 DIAGNOSTIC disabled [D5 :D0] RESERVED RESERVED Configuration register: 2-step measurement The 2-step temperature measurement has a precision of about ±0.3°C (with RREF @ 0.01% of tolerance) which is good enough in most of pH meter applications. (4) 3-step measurement This method requires 3 acquisitions and a precision resistor (RREF) connected between CAL and GND pin, (the RTD is always connected between RTD and GND pin). The first two acquisitions measure the voltage across the precision resistor in 2 different conditions (2 different exciting current and 2 PGA gains) in order to remove the uncertainty of the current source value and the offset of the path. The third acquisition measures the voltage across the RTD (similar to the 1-step measure), in this case the formula to calculate the temperature is more complicate in order to take in account the non-ideality of the system (offset, source current error). where alpha is the thermal coefficient of the RTD (it depends on the selected Ptres); Ptres_nominal is the value of the Ptres at 0degC. (5) where VOUT_PtRES is the amplified voltage across the RTD at VOUT pin (ground referred), when the LMP91200 is configured according to Table 4. www.ti.com 10 V/V TABLE 4. The 1-step temperature measurement has a precision of about ±3°C. PtRES_calculated=(VOUT_PtRES/PGA_GAIN)/I_true 100µA (Pt1000) 1 mA (Pt100) Leave these bits as they have been configured for the pH measurement. Configuration register: 1-step measurement Temp(°C) = (PtRES_calculated – PtRES_nominal) / alpha (7) TABLE 3. TABLE 2. Bit (6) 20 (8) where alpha is the thermal coefficient of the RTD (it depends on the selected Ptres); Ptres_nominal is the value of the Ptres at 0degC. PtRES_calculated=((VOUT_PtRES/PGA_GAIN)-Vos)/ I_true (9) (10) Name (11) MEAS_MODE 1 Temp measurement D14 I_MUX 1 RCAL [D13:D12] I_VALUE 01 11 D11 0 PGA (12) 200µA (Pt1000) 2 mA (Pt100) 5 V/V [D10 :D8] VCM Leave these bits as they have been configured for the pH measurement. D7 VOCM 1 GND D6 DIAG_EN 0 DIAGNOSTIC disabled [D5 :D0] RESERVED RESERVED TABLE 6. Bit Name Description D15 MEAS_MODE 1 Temp measurement D14 I_MUX 1 RCAL [D13:D12] I_VALUE 00 10 D11 1 PGA 10 V/V [D10 :D8] VCM D7 1 VOCM Description MEAS_MODE 1 Temp measurement D14 I_MUX 0 RTD [D13:D12] I_VALUE 00 10 D11 1 PGA 100µA (Pt1000) 1 mA (Pt100) 10 V/V [D10 :D8] VCM Leave these bits as they have been configured for the pH measurement. D7 VOCM 1 GND D6 DIAG_EN 0 DIAGNOSTIC disabled [D5 :D0] RESERVED RESERVED Layout Consideration In pH measurement, due to the high impedance of the ph Electrode, careful circuit layout and assembly are required. Guarding techniques are highly recommended to reduce parasitic leakage current by isolating the LMP91200’s input from large voltage gradients across the PC board. A guard is a low impedance conductor that surrounds an input line and its potential is raised to the input line’s voltage. The input pin should be fully guarded as shown in Figure 4.The guard traces should completely encircle the input connections. In addition, they should be located on both sides of the PCB and be con- 100µA (Pt1000) 1 mA (Pt100) Leave these bits as they have been configured for the pH measurement. Name D15 Diagnostic Feature The diagnostic function allows detecting the presence of the sensor and checking the connection of the sensor. A further analysis of the answer of the pH probe to the diagnostic stimulus allows estimating the aging of the pH probe. With the diagnostic function is possible to change slightly (+/- 5% VREF) the Common mode voltage. If the sensor is present it reacts, this reaction gives some information on the status of the connection, the presence of the sensor and its aging. In fact a typical symptom of the aging of a pH probe is the slowness in the answer. It means that a pH probe answers with a smoother step to the diagnostic stimulus as its age increases. The procedure is enabled and disabled by SPI (refer to Configuration Register). Until bit D6 is at low logic level, VCM stays at the programmed voltage independently by the SDO_DIAG pin status. When bit D6 is tied at high logic level, on the first rising edge of SDO_DIAG, a positive pulse is generate. At the second positive rising edge of SDO_DIAG pin, the positive pulse ends. At the third positive rising edge of SDO_DIAG a negative pulse is generated. At the forth positive rising edge of the SDO_DIAG the negative pulse ends and the routine is stopped and cannot restart until bit D6 is set again at 1. Description D15 DIAGNOSTIC disabled The 3-step temperature measurement can reach a precision as high as ±0.1°C (with RREF @ 0.01% of tolerance) when the analog signal is acquired by at least 16 bit ADC. With lower number of bit ADC this method gives the same result of the 2-step measurement due to the low voltage offset of the signal path. As rule of thumb, the 3-step temperature measurement gives good result if he the LSB of the ADC is less than the input offset of the PGA. TABLE 5. Bit RESERVED Configuration register: 3-step measurement Inserting Equation 9, Equation 10 and Equation 11 in Equation 8 the temperature is given by the following equation: Temp(°C) = (((VOUT_PtRES/PGA_GAIN)(VOUT_RREF0-VOUT_RREF1)/5)/((2*VOUT_RREF1VOUT_RREF0)/(10*RREF))– PtRES_nominal) /alpha 0 RESERVED Bit where VOUT_RREF0 is the amplified voltage across the RREF at VOUT pin (ground referred), when the LMP91200 is configured according to Table 5. VOUT_RREF 1is the amplified voltage across the RREF at VOUT pin (ground referred), when the LMP91200 is configured according to Table 6. I_true=(2*VOUT_RREF1-VOUT_RREF0)/(10*RREF) DIAG_EN [D5 :D0] TABLE 7. where VOUT_PtRES is the amplified voltage across the RTD at VOUT pin (ground referred), when the LMP91200 is configured according to Table 7. I_true is the real current which alternatively flows in the external precison resistance RREF and in the RTD. PGA_GAIN is the selected gain of the PGA. Vos is the offset of the path. Vos=(VOUT_RREF0-VOUT_RREF1)/5 D6 GND 21 www.ti.com LMP91200 Temp(°C) = (PtRES_calculated – PtRES_nominal) / alpha LMP91200 nected together. The LMP91200 makes the guard ring easy to be implemented without any other external op amp. The ring needs to be connected to the guard pins (GUARD1 and GUARD2) which are at the same potential of the INP pin. Solder mask should not cover the input and the guard area including guard traces on either side of the PCB. Sockets are not recommended as they can be a significant leakage source. After assembly, a thorough cleaning using commercial solvent is necessary. In Figure 4 is showed a typical guard ring circuit when the LMP912000 is interfaced to a pH probe trough a triaxial cable/ connector, usually known as 'TRIAX'. The signal conductor and the guard of the triax should be kept at the same potential; therefore, the leakage current between them is practically zero. Since triax has an extra layer of insulation and a second www.ti.com conducting sheath, it offers greater rejection of interference than coaxial cable/connector. 30165570 FIGURE 4. Circuit Board Guard Layout 22 LMP91200 Physical Dimensions inches (millimeters) unless otherwise noted 16-Pin TSSOP NS Package Number MTC16 23 www.ti.com LMP91200 Configurable AFE for Low-Power Chemical Sensing Applications Notes www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications. TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated products in automotive applications, TI will not be responsible for any failure to meet such requirements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP® Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energy and Lighting www.ti.com/energy Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Mobile Processors www.ti.com/omap Wireless Connectivity www.ti.com/wirelessconnectivity TI E2E Community Home Page e2e.ti.com Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright © 2012, Texas Instruments Incorporated