LMP91200

+

± pH

BUFFER

VCM

BUFFER

VDD

VDD

GND

GND

MCU

VOUT

ADC

VOCM

VREF

GND

VCMHI

NC

NC

GUARD1

GUARD2

INP

VCM

GND

pH Electrode

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An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

LMP91200

SNAS571E – JANUARY 2012 – REVISED FEBRUARY 2016

LMP91200 Configurable AFE for Low-Power Chemical-Sensing Applications

1

1 Features

1

•

Active Guarding

•

Key Specifications

Unless otherwise noted, typical values at

TA = 25°C, VS = (VDD-GND) = 3.3 V

–

pH Buffer Input Bias Current (0 < VINP < 3.3 V)

–

Maximum at 25°C: ±125 fA

–

Maximum at 85°C: ±445 fA

–

pH Buffer Input Bias Current

(–500 mV < VINP– VCM < 500 mV),

VS = (VDD – GND) = 0 V

–

Maximum at 25°C: ±600 fA

–

Maximum at 85°C: ±6.5 pA

–

pH Buffer Input Offset Voltage: ±200 µV

–

pH Buffer Input Offset Voltage Drift: ±2.5

μV/°C

–

Supply Current: 50

μA

–

Supply Voltage: 1.8 V to 5.5 V

–

Operating Temperature Range: –40°C to

125°C

–

Package: 16-Pin TSSOP

2 Applications

•

pH Sensor Platforms

3 Description

The LMP91200 device is a 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 1.8 V to 5.5

V. 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. Two guard pins provide

support

for

high

parasitic

impedance

wiring.

Depending

on

the

configuration,

total

current

consumption for the device is 50 µA while measuring

pH. Available in a 16-pin TSSOP package, the

LMP91200 operates from –40°C to +125°C.

Device Information(1)

PART NUMBER

PACKAGE

BODY SIZE (NOM)

LMP91200

TSSOP (16)

5.00 mm × 4.40 mm

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

Typical Application