AD8232
Single-Lead, Heart Rate Monitor Front End
Manufacturer
adi
Overview
Part: AD8232 from Analog Devices
Type: Single-Lead ECG Front End
Key Specs:
- Low supply current: 170 µA (typical)
- Common-mode rejection ratio: 80 dB (dc to 60 Hz)
- High signal gain: G = 100
- Accepts half cell potential: up to ±300 mV
- Single-supply operation: 2.0 V to 3.5 V
- ESD rating: 8 kV HBM
Features:
- Fully integrated single-lead ECG front end
- Two or three electrode configurations
- 2-pole adjustable high-pass filter
- 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
- Integrated reference buffer generates virtual ground
- Rail-to-rail output
- Internal RFI filter
- Shutdown pin
- Qualified for automotive applications
Applications:
- Fitness and activity heart rate monitors
- Portable ECG
- Remote health monitors
- Gaming peripherals
- Biopotential signal acquisition
Package:
- LFCSP: 20-lead, 4 mm × 4 mm
- LFCSP_SS: 20-lead, 4 mm × 4 mm
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 and LFCSP_SS package
Qualified for automotive applications
Applications
Fitness and activity heart rate monitors Portable ECG Remote health monitors Gaming peripherals Biopotential signal acquisition
Pin Configuration
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
| Pin No. | Mnemonic | Description |
|---|---|---|
| 1 | HPDRIVE | High-Pass Driver Output. Connect HPDRIVE to the capacitor in the first high-pass filter. The AD8232 drives this pin to keep HPSENSE at the same level as the reference voltage. |
| 2 | +IN | Instrumentation Amplifier Positive Input. +IN is typically connected to the left arm (LA) electrode. |
| 3 | −IN | Instrumentation Amplifier Negative Input. −IN is typically connected to the right arm (RA) electrode. |
| 4 | RLDFB | Right Leg Drive Feedback Input. RLDFB is the feedback terminal for the right leg drive circuit. |
| 5 | RLD | Right Leg Drive Output. Connect the driven electrode (typically, right leg) to the RLD pin. |
| 6 | SW | Fast Restore Switch Terminal. Connect this terminal to the output of the second high-pass filter. |
| 7 | OPAMP+ | Operational Amplifier Noninverting Input. |
| 8 | REFOUT | Reference Buffer Output. The instrumentation amplifier output is referenced to this potential. Use REFOUT as a virtual ground for any point in the circuit that needs a signal reference. |
| 9 | OPAMP− | Operational Amplifier Inverting Input. |
| 10 | OUT | Operational Amplifier Output. The fully conditioned heart rate signal is present at this output. OUT can be connected to the input of an ADC. |
| 11 | LOD− | Leads Off Comparator Output. In dc leads off detection mode, LOD− is high when the electrode to −IN is disconnected, and it is low when connected. In ac leads off detection mode, LOD− is always low. |
| 12 | LOD+ | Leads Off Comparator Output. In dc leads off detection mode, LOD+ is high when the +IN electrode is disconnected, and it is low when connected. In ac leads off detection mode, LOD+ is high when either the −IN or +IN electrode is disconnected, and it is low when both electrodes are connected. |
| 13 | SDN | Shutdown Control Input. Drive SDN low to enter the low power shutdown mode. |
| 14 | AC/DC | Leads Off Mode Control Input. Drive the AC/DC pin low for dc leads off mode. Drive the AC/DC pin high for ac leads off mode. |
| 15 | FR | Fast Restore Control Input. Drive FR high to enable fast recovery mode; otherwise, drive it low. |
| 16 | GND | Power Supply Ground. |
| 17 | +VS | Power Supply Terminal. |
| 18 | REFIN | Reference Buffer Input. Use REFIN, a high impedance input terminal, to set the level of the reference buffer. |
| 19 | IAOUT | Instrumentation Amplifier Output Terminal. |
| 20 | HPSENSE | High-Pass Sense Input for Instrumentation Amplifier. Connect HPSENSE to the junction of R and C that sets the corner frequency of the dc blocking circuit. |
| EP | Exposed Pad. Connect the exposed pad to GND or leave it unconnected. |
Absolute Maximum Ratings
Table 2.
| Parameter | Rating |
|---|---|
| Supply Voltage | 3.6 V |
| Output Short-Circuit Current Duration | Indefinite |
| Maximum Voltage, Any Terminal1 | +VS + 0.3 V |
| Minimum Voltage, Any Terminal1 | −0.3 V |
| Storage Temperature Range | −65°C to +125°C |
| Operating Temperature Range | |
| AD8232ACPZ | −40°C to +85°C |
| AD8232WACSZ | −40°C to +105°C |
| Maximum Junction Temperature | 140°C |
| θJA Thermal Impedance2 | 48°C/W |
| θJC Thermal Impedance | 4.4°C/W |
| ESD Rating | |
| Human Body Model (HBM) | 8 kV |
| Charged Device Model (FICDM) | 1.25 kV |
| Machine Model (MM) | 200 V |
1 This level or the maximum specified supply voltage, whichever is the lesser, indicates the superior voltage limit for any terminal. If input voltages beyond the specified minimum or maximum voltages are expected, place resistors in series with the inputs to limit the current to less than 5 mA.
Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability.
ESD CAUTION
2 θJA is specified for a device in free air on a 4-layer JEDEC board.
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