Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsData collecting ICsData acquisition IC - Analog front end (AFE) 8 Bit WSON 14

I2C INTERFACE

AND

CONTROL

REGISTERS

VREF

VDD

AGND

VOUT

SCL

VREF

DIVIDER

SDA

Load

DIAGNOSTIC

MENB

DGND

TIA

3-Lead

Electrochemical

Cell

MSP430

LMP91002

www.ti.com

SNIS163A –APRIL 2012–REVISED MARCH 2013

LMP91002 Sensor AFE System: Configurable AFE Potentiostat for Low-Power Chemical

Sensing Applications

Check for Samples: LMP91002

FEATURES

DESCRIPTION

The LMP91002 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 3.6 V

applications. It provides a complete signal path

• Supply Current (Average Over Time) <10 µA

solution between a not biased gas sensor and a

microcontroller generating an output voltage

• Cell Conditioning Current Up to 10 mA

proportional to the cell current. The LMP91002’s

• Reference Electrode Bias Current (85°C)

programmability enables it support not biased electro-

900pA (Max)

chemical gas sensor with a single design. The

• Output Drive Current 750µA

LMP91002 supports gas sensitivities over a range of

0.5 nA/ppm to 9500 nA/ppm. It also allows for an

• Complete Potentiostat Circuit to Interface to

easy conversion of current ranges from 5μA to 750μA

Most Not Biased Gas Sensors

full scale. The LMP91002’s transimpedance amplifier

• Low Bias Voltage Drift

(TIA) gain is programmable through the I2C interface.

• Programmable TIA Gain 2.75kΩ to 350kΩ

The I2C interface can also be used for sensor

diagnostics. The LMP91002 is optimized for micro-

• I

C Compatible Digital Interface

power applications and operates over a voltage range

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

of 2.7V to 3.6V. The total current consumption can be

• Package 14 pin WSON

less than 10μA. Further power savings are possible

by switching off the TIA amplifier and shorting the

• Supported by Webench Sensor AFE Designer

reference electrode to the working electrode with an

internal switch.

APPLICATIONS

• Gas Detector

• Amperometric Applications

• Electrochemical Blood Glucose Meter

Typical Application

Figure 1. AFE Gas Detector

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.

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 (26 pages)

PAGE 1
LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 LMP91002 Sensor AFE System: Configurable AFE Potentiostat for Low-Power Chemical Sensing Applications Check for Samples: LMP91002 FEATURES DESCRIPTION • • • • • The LMP91002 is a programmable Analog Front End (AFE) for use in micro-power electrochemical sensing applications. It provides a complete signal path solution between a not biased gas sensor and a microcontroller generating an output voltage proportional to the cell current.
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LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 www.ti.com 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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LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 Absolute Maximum Ratings (1) (2) (3) Human Body Model ESD Tolerance (4) 2kV Charge-Device Model 1kV Machine Model 200V Voltage between any two pins 6.
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LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 www.ti.com Electrical Characteristics (1) Unless otherwise specified, all limits ensured 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. Symbol Typ (3) Max (2) 3-lead amperometric cell mode MODECN = 0x03 10 15 13.5 Standby mode MODECN = 0x02 6.5 10 8 Deep Sleep mode MODECN = 0x00 0.6 1 0.
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LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 Electrical Characteristics(1) (continued) Unless otherwise specified, all limits ensured 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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LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 www.ti.com Timing Characteristics (1) Unless otherwise specified, all limits ensured 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 in Figure 3. Symbol Parameter 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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LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 Typical Performance Characteristics Unless otherwise specified, TA = 25°C, VS=(VDD – AGND), 2.7V
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LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified, TA = 25°C, VS=(VDD – AGND), 2.7V
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LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Unless otherwise specified, TA = 25°C, VS=(VDD – AGND), 2.7V
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LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 www.ti.com Function Description GENERAL The LMP91002 is a programmable AFE for use in micropower chemical sensing applications. The LMP91002 is designed for 3-lead not biased gas sensors and for 2 leads galvanic cell. This device provides all of the functionality for detecting changes in gas concentration based on a delta current at the working electrode. The LMP91002 generates an output voltage proportional to the cell current.
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LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 Control amplifier The control amplifier (A1 op amp in Figure 17) provides initial charge 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). It can be powered down to reduce system power consumption.
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LMP91002 SNIS163A – APRIL 2012 – 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 MENB (continued) SCL (continued) 1 SDA (continued) D7 D6 D5 D4 D3 D2 D1 D0 Frame 2 Internal Address Register Byte from Master Ack by LMP91000 9 D6 D5 D4 D3 D2 D1 D0 Ack Stop by by Master LMP91000 Frame 3 Data Byte Figure 18.
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LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 REGISTERS The registers are used to configure the LMP91002. If writing to a reserved bit, user must write only 0. Readback value is unspecified and should be discarded. Table 1.
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LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 www.ti.com REFCN -- Reference Control Register (address 0x11) The parameters in the Reference control register allow the configuration of the Internal zero, and Reference source. When the Reference source is external, the reference is provided by a reference voltage connected to the VREF pin. In this condition the Internal Zero is defined as a percentage of VREF voltage instead of the supply voltage.
PAGE 15
LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 GAS SENSOR INTERFACE The LMP91002 supports both 3-lead and 2-lead gas sensors. Most of the toxic gas sensors are amperometric cells with 3 leads (Counter, Worker and Reference). These leads should be connected to the LMP91002 in the potentiostat topology. 3-lead Amperometric Cell In Potentiostat Configuration Most of the amperometric cell have 3 leads (Counter, Reference and Working electrodes).
PAGE 16
LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 www.ti.com 2-lead Galvanic Cell in Potentiostat Configuration When the LMP91002 is interfaced to a galvanic cell (for instance to an Oxygen gas sensor) referred to a reference, the Counter and the Reference pin of the LMP91002 are shorted together and connected to negative electrode of the galvanic cell. The positive electrode of the galvanic cell is then connected to the Working pin of the LMP91002.
PAGE 17
LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 APPLICATION INFORMATION CONNECTION OF MORE THAN ONE LMP91002 TO THE I2C BUS The LMP91002 comes out with a unique and fixed I2C slave address. It is still possible to connect more than one LMP91002 to an I2C bus and select each device using the MENB pin. The MENB simply enables/disables the I2C communication of the LMP91002.
PAGE 18
LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 www.ti.com SCL A0 SDA SCL MENB MENB SCL SDA I2C EEPROM LMP91000 SDA Figure 24. SMART GAS SENSOR AFE SMART GAS SENSOR AFES ON I2C BUS The connection of Smart gas sensor AFEs on the I2C bus is the natural extension of the previous concepts. Also in this case the microcontroller starts communication asserting 1 out of N MENB signals where N is the total number of smart gas sensor AFE connected to the I2C bus.
PAGE 19
LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 This results in an average power consumption of approximately 7.8 µA. This can potentially be further reduced, by using the Standby mode between gas measurements. It may even be possible, depending on the sensor used, to go into deep sleep for some time between measurements, further reducing the average power consumption. Table 2.
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LMP91002 SNIS163A – APRIL 2012 – REVISED MARCH 2013 20 www.ti.
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LMP91002 www.ti.com SNIS163A – APRIL 2012 – REVISED MARCH 2013 REVISION HISTORY Changes from Original (March 2013) to Revision A • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing LMP91002SD/NOPB WSON NHL 14 LMP91002SDE/NOPB WSON NHL LMP91002SDX/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 8-Apr-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LMP91002SD/NOPB WSON NHL 14 1000 213.0 191.0 55.0 LMP91002SDE/NOPB WSON NHL 14 250 213.0 191.0 55.0 LMP91002SDX/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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