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.