Single-Lead, Heart Rate Monitor Front End

Data Sheet

AD8232

Rev. B

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FEATURES

Fully integrated single-lead ECG front end

Low supply current: 170 µA (typical)

Common-mode rejection ratio: 80 dB (dc to 60 Hz)

Two or three electrode configurations

High signal gain (G = 100) with dc blocking capabilities

2-pole adjustable high-pass filter

Accepts up to ±300 mV of half cell potential

Fast restore feature improves filter settling

Uncommitted op amp

3-pole adjustable low-pass filter with adjustable gain

Leads off detection: ac or dc options

Integrated right leg drive (RLD) amplifier

Single-supply operation: 2.0 V to 3.5 V

Integrated reference buffer generates virtual ground

Rail-to-rail output

Internal RFI filter

8 kV HBM ESD rating

Shutdown pin

20-lead 4 mm × 4 mm LFCSP package

APPLICATIONS

Fitness and activity heart rate monitors

Portable ECG

Remote health monitors

Gaming peripherals

Biopotential signal acquisition

FUNCTIONAL BLOCK DIAGRAM

Figure 1.

GENERAL DESCRIPTION

The AD8232 is an integrated signal conditioning block for ECG

and other biopotential measurement applications. It is designed

to extract, amplify, and filter small biopotential signals in the

presence of noisy conditions, such as those created by motion or

remote electrode placement. This design allows for an ultralow

power analog-to-digital converter (ADC) or an embedded

microcontroller to acquire the output signal easily.

The AD8232 can implement a two-pole high-pass filter for

eliminating motion artifacts and the electrode half-cell potential.

This filter is tightly coupled with the instrumentation architec-

ture of the amplifier to allow both large gain and high-pass

filtering in a single stage, thereby saving space and cost.

An uncommitted operational amplifier enables the AD8232 to

create a three-pole low-pass filter to remove additional noise.

The user can select the frequency cutoff of all filters to suit

different types of applications.

To improve common-mode rejection of the line frequencies

in the system and other undesired interferences, the AD8232

includes an amplifier for driven lead applications, such as right

leg drive (RLD).

The AD8232 includes a fast restore function that reduces the

duration of otherwise long settling tails of the high-pass filters.

After an abrupt signal change that rails the amplifier (such as a

leads off condition), the AD8232 automatically adjusts to a

higher filter cutoff. This feature allows the AD8232 to recover

quickly, and therefore, to take valid measurements soon after

connecting the electrodes to the subject.

The AD8232 is available in a 4 mm × 4 mm, 20-lead LFCSP

package. Performance is specified from 0°C to 70°C and is

operational from −40°C to +85°C.

LOD–

LOD+

AD8232

GND

OUT

OPAMP–

REFOUT

OPAMP+

SW

REFIN

IAOUT

HPSENSE

HPDRIVE

+IN

–IN

RLD

RLDFB

FR

SDN

AC/DC

LEADS-OFF

DETECTION

10kΩ

10kΩ

150kΩ

S1

S2

20

2

1

3

4

19

18

17

16

15

IA

A3

5

6

7

8

9

A1

10

A2

14

13

12

11

C2

C1