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LMP91000

www.ti.com

SNAS506H –JANUARY 2011–REVISED MARCH 2013

LMP91000 Sensor AFE System: Configurable AFE Potentiostat for Low-Power Chemical

Sensing Applications

Check for Samples: LMP91000

FEATURES

DESCRIPTION

The LMP91000 is a programmable Analog Front End

• Typical Values, T

= 25°C

(AFE) for use in micro-power electrochemical sensing

• Supply Voltage 2.7 V to 5.25 V

applications. It provides a complete signal path

• Supply Current (Average Over Time) <10 µA

solution between a sensor and a microcontroller that

generates an output voltage proportional to the cell

• Cell Conditioning Current up to 10 mA

current. The LMP91000’s programmability enables it

• Reference Electrode Bias Current (85°C)

to support multiple electrochemical sensors such as

900pA (max)

3-lead toxic gas sensors and 2-lead galvanic cell

• Output Drive Current 750µA

sensors with a single design as opposed to the

multiple discrete solutions. The LMP91000 supports

• Complete Potentiostat Circuit to Interface to

gas sensitivities over a range of 0.5 nA/ppm to 9500

Most Chemical Cells

nA/ppm. It also allows for an easy conversion of

• Programmable Cell Bias Voltage

current ranges from 5µA to 750µA full scale.

• Low Bias Voltage Drift

The LMP91000’s adjustable cell bias and

• Programmable TIA gain 2.75kΩ to 350kΩ

transimpedance amplifier (TIA) gain are

• Sink and Source Capability

programmable through the I

C interface. The I

interface can also be used for sensor diagnostics. An

• I

C Compatible Digital Interface

integrated temperature sensor can be read by the

• Ambient Operating Temperature -40°C to 85°C

user through the VOUT pin and used to provide

• Package 14 pin WSON

additional signal correction in the µC or monitored to

verify temperature conditions at the sensor.

• Supported by WEBENCH

Sensor AFE

Designer

The LMP91000 is optimized for micro-power

applications and operates over a voltage range of

APPLICATIONS

2.7V to 5.25V. The total current consumption can be

less than 10μA. Further power savings are possible

• Chemical Species Identification

by switching off the TIA amplifier and shorting the

• Amperometric Applications

reference electrode to the working electrode with an

internal switch.

• Electrochemical Blood Glucose Meter

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2WEBENCH is a registered trademark of Texas Instruments.

3All other trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (30 pages)

PAGE 1
LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 LMP91000 Sensor AFE System: Configurable AFE Potentiostat for Low-Power Chemical Sensing Applications Check for Samples: LMP91000 FEATURES DESCRIPTION • • • • • The LMP91000 is a programmable Analog Front End (AFE) for use in micro-power electrochemical sensing applications. It provides a complete signal path solution between a sensor and a microcontroller that generates an output voltage proportional to the cell current.
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LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com Typical Application VDD VREF SCL LMP91000 3-Lead Electrochemical Cell CE VARIABLE BIAS + A1 I2C INTERFACE AND CONTROL REGISTERS VREF DIVIDER SDA CONTROLLER MENB - CE RE RE TEMP SENSOR WE WE VOUT + - DGND TIA RLoad RTIA AGND C2 C1 Figure 1. AFE Gas Detector Connection Diagram DGND 1 14 CE MENB RE SCL WE SDA VREF DAP NC C1 VDD C2 AGND 7 8 VOUT Figure 2.
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LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 PIN DESCRIPTIONS (continued) Name Pin CE 14 DAP Description Counter Electrode. Output to drive Counter Electrode of the chemical sensor Connect to AGND These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
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LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 Electrical Characteristics www.ti.com (1) Unless otherwise specified, all limits guaranteed for TA = 25°C, VS=(VDD – AGND), VS=3.3V and AGND = DGND =0V, VREF= 2.5V, Internal Zero= 20% VREF. Boldface limits apply at the temperature extremes. Parameter Test Conditions Min (2) Typ (3) Max (2) Units POWER SUPPLY SPECIFICATION IS Supply Current 3-lead amperometric cell mode MODECN = 0x03 10 15 13.5 Standby mode MODECN = 0x02 6.
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LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 Electrical Characteristics (1) (continued) Unless otherwise specified, all limits guaranteed for TA = 25°C, VS=(VDD – AGND), VS=3.3V and AGND = DGND =0V, VREF= 2.5V, Internal Zero= 20% VREF. Boldface limits apply at the temperature extremes.
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LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com Electrical Characteristics (1) (continued) Unless otherwise specified, all limits guaranteed for TA = 25°C, VS=(VDD – AGND), VS=3.3V and AGND = DGND =0V, VREF= 2.5V, Internal Zero= 20% VREF. Boldface limits apply at the temperature extremes. Parameter TIA_GAIN Test Conditions Min (2) Typ Transimpedance gain accuracy Linearity Programmable TIA Gains TIA_ZV Internal zero voltage Programmable Load % 2.75 3.
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LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 Timing Characteristics (1) Unless otherwise specified, all limits guaranteed for TA = 25°C, VS=(VDD – AGND), VS=3.3V and AGND = DGND =0V, VREF= 2.5V, Internal Zero= 20% VREF. Boldface limits apply at the temperature extremes. Refer to Timing Diagram. Parameter Test Conditions Min Typ Max Units 100 kHz fSCL Clock Frequency 10 tLOW Clock Low Time 4.7 µs tHIGH Clock High Time 4.0 µs 4.
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LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics Unless otherwise specified, TA = 25°C, VS=(VDD – AGND), 2.7V
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LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Unless otherwise specified, TA = 25°C, VS=(VDD – AGND), 2.7V
PAGE 10
LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified, TA = 25°C, VS=(VDD – AGND), 2.7V
PAGE 11
LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Unless otherwise specified, TA = 25°C, VS=(VDD – AGND), 2.7V
PAGE 12
LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com FUNCTION DESCRIPTION GENERAL The LMP91000 is a programmable AFE for use in micropower chemical sensing applications. The LMP91000 is designed for 3-lead single gas sensors and for 2-lead galvanic cell sensors. This device provides all of the functionality for detecting changes in gas concentration based on a delta current at the working electrode. The LMP91000 generates an output voltage proportional to the cell current.
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LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 Control amplifier The control amplifier (A1 op amp in Figure 25) has two tasks: a) providing initial charge to the sensor, b) providing a bias voltage to the sensor. A1 has the capability to drive up to 10mA into the sensor in order to to provide a fast initial conditioning. A1 is able to sink and source current according to the connected gas sensor (reducing or oxidizing gas sensor).
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LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com Table 1.
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LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 V-1399mV=((1154mV - 1399mV)/(50°C -20°C))*(T-20°C) V-1399mV= -8.16mV/°C*(T-20°C) V=(-8.16mV/°C)*T+1562.2mV Using this method of linear approximation, the transfer function can be approximated for one or more temperature ranges of interest. I2C INTERFACE The I2C compatible interface operates in Standard mode (100kHz).
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LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com MENB 1 9 1 9 SCL SDA A6 A5 A4 A3 A2 A1 A0 R/W D7 Ack by LMP91000 Start by Master Frame 1 Serial Bus Address Byte from Master D6 D5 D4 D3 D2 D1 Frame 2 Internal Address Register Byte from Master D0 Ack by LMP91000 Stop by Master Figure 27.
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LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 LOCK -- Protection Register (address 0x01) The lock bit enables and disables the writing of the TIACN and the REFCN registers. In order to change the content of the TIACN and the REFCN registers the lock bit needs to be set to “0”.
PAGE 18
LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 Bit [3:0] www.ti.com Name BIAS Function BIAS selection (Percentage of the source reference) 0000 0% (default) 0001 1% 0010 2% 0011 4% 0100 6% 0101 8% 0110 10% 0111 12% 1000 14% 1001 16% 1010 18% 1011 20% 1100 22% 1101 24% MODECN -- Mode Control Register (address 0x12) The Parameters in the Mode register allow the configuration of the Operation Mode of the LMP91000.
PAGE 19
LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 VDD VREF LMP91000 3-Lead Electrochemical Cell CE + A1 SCL VARIABLE BIAS VREF DIVIDER I2C INTERFACE AND CONTROL REGISTERS SDA MENB - CE RE RE TEMP SENSOR WE WE VOUT + - DGND TIA RLoad RTIA C1 C2 AGND Figure 29.
PAGE 20
LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com VE2-wire Sensor such as Oxygen NC VE+ VDD VREF SCL LMP91000 I2C INTERFACE AND CONTROL REGISTERS VARIABLE BIAS + A1 CE VREF DIVIDER SDA MENB - RE TEMP SENSOR WE DGND VOUT + TIA RLoad RTIA C2 C1 AGND Figure 30.
PAGE 21
LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 VDD VREF LMP91000 2-wire Sensor such as Oxygen CE + A1 SCL VARIABLE BIAS VREF DIVIDER I2C INTERFACE AND CONTROL REGISTERS SDA MENB - VERE NC TEMP SENSOR VE+ WE VOUT + - DGND TIA RLoad RTIA C1 C2 AGND Figure 31. 2-Lead Galvanic Cell In Potentiostat Configuration APPLICATION INFORMATION CONNECTION OF MORE THAN ONE LMP91000 TO THE I2C BUS The LMP91000 comes out with a unique and fixed I2C slave address.
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LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 SCL GPIO N GPIO 3 GPIO 2 µC SDA MENB SCL LMP91000 SDA MENB LMP91000 SDA MENB SCL SDA GPIO 1 SCL LMP91000 LMP91000 MENB www.ti.com SCL SDA Figure 32. More than one LMP91000 on I2C bus SMART GAS SENSOR ANALOG FRONT END The LMP91000 together with an external EEPROM represents the core of a SMART GAS SENSOR AFE.
PAGE 23
LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 SMART SENSOR AFE SMART SENSOR AFE SCL SMART SENSOR AFE GPIO 2 GPIO 1 I2C EEPROM SDA SCL SDA MENB LMP91000 A0 I2C EEPROM A0 SCL SDA MENB SDA A0 LMP91000 SCL I2C EEPROM SCL SCL SDA MENB LMP91000 SDA www.ti.com GPIO N µC SCL SDA Figure 34.
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LMP91000 SNAS506H – JANUARY 2011 – REVISED MARCH 2013 www.ti.com SENSOR TEST PROCEDURE The LMP91000 has all the hardware and programmability features to implement some test procedures. The purpose of the test procedure is to: a. test proper function of the sensor (status of health) b. test proper connection of the sensor to the LMP91000 The test procedure is very easy. The variable bias block is user programmable through the digital interface.
PAGE 25
LMP91000 www.ti.com SNAS506H – JANUARY 2011 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision G (March 2013) to Revision H • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
PAGE 26
PACKAGE OPTION ADDENDUM www.ti.
PAGE 27
PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing LMP91000SD/NOPB WSON NHL 14 LMP91000SDE/NOPB WSON NHL LMP91000SDX/NOPB WSON NHL SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 1000 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 14 250 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 14 4500 330.0 12.4 4.3 4.3 1.3 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LMP91000SD/NOPB WSON NHL 14 1000 213.0 191.0 55.0 LMP91000SDE/NOPB WSON NHL 14 250 213.0 191.0 55.0 LMP91000SDX/NOPB WSON NHL 14 4500 367.0 367.0 35.
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MECHANICAL DATA NHL0014B SDA14B (Rev A) www.ti.
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