PS25255
EPIC Ultra High Impedance ECG Sensor
Advance Information
Data Sheet 291955 issue 1
FEATURES
•
•
•
•
•
•
•
•
Ultra high input resistance, typically 20G .
Low supply current 1.4mA
Dry-contact capacitive coupling.
Input capacitance as low as 15pF.
Lower -3dB point typically 200mHz.
Upper -3dB point typically 20kHz.
Operates with bipolar power supply from ±2.4V to
±5.5V.
Sensors supplied in a custom package with exposed
pins for surface mount assembly.
Ordering Information
PS25255
Custom package
-25° to +75°
C
C
Plessey Semiconductors Electric Potential
Integrated Circuit (EPIC) product line targets a
range of applications.
The PS25255 is an ultra high impedance solid
state ECG (electrocardiograph) sensor. It can
be used as a dry contact ECG sensor without
the need for potentially dangerous low
impedance circuits across the heart. The
resolution available is as good as or better
than conventional wet electrodes.
The device uses active feedback techniques to
both lower the effective input capacitance of the
sensing element (Cin) and boost the input
resistance (Rin). These techniques are used to
realise a sensor with a frequency response
suitable for both diagnostic and monitoring ECG
applications.
APPLICATIONS
•
Contact ECG signal detection for:
•
Non-critical patient monitoring
equipment.
•
Emergency response diagnostics.
•
Lifestyle sports and health products.
•
Suitable for long-term and remote
monitoring.
Fig. 1 PS25255 (top and bottom)
Fig. 2 Internal circuit of EPIC ECG Sensor
Data Sheet 291955 issue 1
Plessey Semiconductors Ltd.
Design & Technology Centre, Delta 500, Delta Business Park, Great Western Way, Swindon, UK SN5 7XE
Tel: +44 1793 518000
Fax: +44 1793 518030
Web:
www.plesseysemi.com
1
PS25255
ELECTRICAL CHARACTERISTICS
C
C,Vdd/Vss ±2.4V to ±5.5V. The electrical characteristics are guaranteed by either production
T
amb
= -25° to +75°
test or by design and characterisation. They apply within the specified ambient temperature and supply voltage
unless otherwise stated.
Characteristics
Min.
Supply voltage
Supply current
Effective input resistance
Effective input capacitance
Voltage Gain (Av)
Coupling capacitance
Lower -3dB point
Upper -3dB point
Noise
±2.4
Value
Typ.
Max.
±5.5
1.4
20
15
10
250
0.20
20.0
tbd
Units
V
mA
G
pF
Conditions
Bipolar supply, Gnd=0V
pF
Hz
kHz
Sensor to skin
Set by internal DC signal rejection
network – coupling capacitor 250pF
-3dB
0.2Hz
20.0kHz
Fig. 3 Typical Bode Plot for EPIC ECG Sensor
Data Sheet 291955 Issue 1
Plessey Semiconductors Ltd.
Design & Technology Centre, Delta 500, Delta Business Park, Great Western Way, Swindon, UK SN5 7XE
Tel: +44 1793 518000
Fax: +44 1793 518030
Web:
www.plesseysemi.com
2
PS25255
PIN ASSIGNMENT
Vdd
Vss
Test points –
keep isolated
Gnd
Bottom View
Output
Pin 1
Fig. 4 Pin Assignment for the PS25255
MECHANICAL DIMENSIONS
A preliminary package diagram is shown below. This is certain to change and so should only be used for
illustration purposes.
10.0
10.0
0.5
9.0
0.5
2.0
1.1
7.8
1.1
0.5
1.1
9.0
10.0
7.8
10.0
0.5
1.1
Top
Side
4x
1.0x1.0
Bottom
Fig. 5 Mechanical Drawing (all dimensions are nominal and in mm)
Data Sheet 291955 Issue 1
Plessey Semiconductors Ltd.
Design & Technology Centre, Delta 500, Delta Business Park, Great Western Way, Swindon, UK SN5 7XE
Tel: +44 1793 518000
Fax: +44 1793 518030
Web:
www.plesseysemi.com
3
PS25255
ELECTROSTATIC DISCHARGE (ESD) PROTECTION
The PS25255 is manufactured using a high performance analog CMOS process. As for all CMOS
components, it is essential that conventional ESD protection protocols be applied for the handling of this
device.
PATENTS
This component and many of the associated applications are covered by the following international
patents:
602 32 911.6-08 (DE)
AU2007228660
CA2646411
CN200780026584.8
EP1451595 (CH)
EP1451595 (ES)
EP1451595 (FR)
EP1451595 (IE)
EP1451595 (IT)
EP1451595 (NL)
EP2002273
EP2047284
EP2174416
GB1118970.1
JP2009-500908
JP4391823
TW097126903
TW1308066
US12/293872
US12/374359
US12/669615
US13/020890
US13/163988
US7885700
Data Sheet 291955 Issue 1
Plessey Semiconductors Ltd.
Design & Technology Centre, Delta 500, Delta Business Park, Great Western Way, Swindon, UK SN5 7XE
Tel: +44 1793 518000
Fax: +44 1793 518030
Web:
www.plesseysemi.com
4
PS25255
APPLICATION OF THE ECG SENSOR
Because of the large coupling capacitance to the body (around 250pF) the EPIC sensor’s internal electrometer can
be used in differential mode to recover true surface potential ECG signals from the surface of the skin. A typical
ECG signal at the surface of the skin is 1mV p-p.
Vdiff
Fig. 7 Differential measurement of body (skin) surface potential to produce ECG trace
Fig. 8 Comparison of two vectors from a pair of EPIC sensors (top)
and two conventional Ag/AgCl electrodes (bottom)
Data Sheet 291955 Issue 1
Plessey Semiconductors Ltd.
Design & Technology Centre, Delta 500, Delta Business Park, Great Western Way, Swindon, UK SN5 7XE
Tel: +44 1793 518000
Fax: +44 1793 518030
Web:
www.plesseysemi.com
5
