MAX86140 datasheet(13/89 Pages) MAXIM

13 / 89 page

Detailed Description

The MAX86140/MAX86141 are complete integrated optical

data acquisition systems, ideal for optical pulse oximetry

and heart rate detection applications. Both parts have

been designed for the demanding requirements of mobile

and wearable devices and require minimal external hardware

components are necessary for integration into a wear-

able device. They include high-resolution, optical readout

signal processing channels with robust ambient light

cancellation and high-current LED driver DACs to form a

complete optical readout signal chain.

The MAX86140/MAX86141 are fully adjustable through

software registers and the digital output data is stored

in a 128-word FIFO within the IC. The FIFO allows the

MAX86140/MAX86141 to be connected to a microcontroller

or processor on a shared bus, where the data is not being

read continuously from the MAX86140/MAX86141’s

registers. Both operate in fully autonomous modes for low

power battery applications.

The MAX86140 consists of a single optical readout channel,

while the MAX86141 incorporates dual optical readout

channels that operate simultaneously. Both parts have

three LED drivers and are well suited for a wide variety of

optical sensing applications.

The MAX86140/MAX86141 operate on a 1.8V main

supply voltage, with a separate 3.1V to 5.0V LED driver

power supply. Both devices have flexible timing and shut-

down configurations as well as control of individual blocks

so an optimized measurement can be made at minimum

power levels.

Optical Subsystem

The optical subsystem in the MAX86140/MAX86141 is

composed of ambient light cancellation (ALC), a continuous-

time sigma-delta ADC, and proprietary discrete time

filter. ALC incorporates a proprietary scheme to cancel

ambient light generated photo diode current, allowing

the sensor to work in high ambient light conditions. The

optical ADC has programmable full-scale ranges of 4μA to

32μA. The internal ADC is a continuous time oversampling

sigma delta converter with 19-bit resolution. The ADC

output data rate can be programmed from 8sps (samples

per second) to 8192sps. The MAX86140 includes a

proprietary discrete time filter to reject 50Hz/60Hz

interference and changing residual ambient light from the

sensor measurements.

The MAX86140/MAX86141 supports Dynamic Power

Down mode (Low-Power mode) in which the power

consumption is decreased between samples. This mode

is only supported for sample rates 128sps and below. For

more details on the power consumption at each sample

rates, refer to the Electrical Characteristics table.

LED Driver

The MAX86140/MAX86141 integrates three precision LED

driver-current DACs that modulate LED pulses for a

variety of optical measurements. The LED current DACs

have 8-bits of dynamic range with four programmable

full-scale ranges of 31mA, 62mA, 94mA, and 124mA. The

LED drivers are low dropout current sources, allowing for

low-noise, power-supply independent LED currents to be

sourced at the lowest supply voltage possible; therefore

minimizing LED power consumption. The LED pulse width

can be programmed from 14.8μs to 117.3μs to allow the

algorithms to optimize SpO2 and HR accuracy at the lowest

dynamic power consumption dictated by the application.

FIFO Configuration

The FIFO is 128 sample depth and is designed to support

various data types, as shown in Table 2. Each sample

width is 3 bytes, which includes a 5-bit tag width. The

tag embedded in the FIFO_DATA is used to identify the

source of each sample data. The description of each Tag

is as shown in Table 3.

LED Sequence Control (address 0x20 ~ 0x22)

The data format in the FIFO, as well as the sequencing of

exposures, are controlled by the LED Sequence Registers

through LEDC1 through LEDC6. There are six LED

Sequence Data Items available, as shown in Table 1. The

exposure sequence cycles through the LED Sequence

bit fields, starting from LEDC1 to LEDC6. The first LED

Sequence field set to NONE (0000) ends the sequence.

www.maximintegrated.com

Maxim Integrated │ 13

MAX86140/

MAX86141

Best-in-Class Optical Pulse Oximeter and

Heart-Rate Sensor for Wearable Health

MAX86140 Datasheet(PDF) 13 Page - Maxim Integrated Products

MAX86140 Datasheet(HTML) 13 Page - Maxim Integrated Products

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