SLAA486B January   2011  – June 2019 MSP430G2452

 

  1.   EKG-Based Heart-Rate Monitor Implementation Using the MSP430G2xx LaunchPad™ Development Kit
    1.     Trademarks
    2. 1 Introduction
    3. 2 Hardware Description
      1. 2.1 Hand Detection Circuit
      2. 2.2 Analog Front End (AFE)
      3. 2.3 Pin Functionality Mapping on the LaunchPad Kit
      4. 2.4 eZ430 RF Target Header
      5. 2.5 Power Supply Setup
    4. 3 Software
    5. 4 References
  2.   A Amplifier Options
    1.     A.1 Instrumentation Amplifier Options
    2.     A.2 Operational Amplifier Options
  3.   B Wired USB Demo With Back-Channel UART
  4.   C Wireless UART Demo With the eZ430 RF Target Board
  5.   D Hardware Schematic Diagrams
  6.   Revision History

A.1 Instrumentation Amplifier Options

This reference design uses the INA332 as the instrumentation amplifier for the analog front end. Table 4 shows other options for the instrumentation amplifier.

Table 4. Instrumentation Amplifier Comparison

Device Name INA321 INA332 INA333
INA321_laa486.gif
INA332_laa486.gif
INA333_laa486.gif
Quiescent current 40 µA/channel 490 μA/channel 50 μA/channel
Shutdown current <1 μA approximately 0.01 μA No shutdown
Bandwidth 500 kHz, G = 5 V/V 2 MHz, G = 25 35 kHz, G = 10
Slew rate 500 kHz, G = 5 V/V 5 V/μs for G = 25 0.16 V/μs for G = 1
Supply voltage 2.7 V to 5.5 V 2.7 V to 5.5 V 1.8 V to 5.5 V
Price/1ku
(listed on http://www.ti.com)		 1.25 0.55 1.80

The INA321 is pin-to-pin compatible with the INA332 and uses a two-resistor feedback network to set the gain. It also offers significantly lower quiescent current, although it costs more. The INA333 has a different architecture in which the gain is set by one resistor. While it lacks a shutdown pin, the quiescent current consumption levels are comparable to the INA321 with the advantage of operating as low as 1.8 V. While the most expensive of the three, the INA333 is ideal for battery-operated portable systems with low-voltage operating range.