3PEAK
Features
TPA8801B
High Sensitivity Current Input Interface
Description
TPA8801B is a high sensitivity current input interface,
which can covert the pA to nA range current signal to 5V
range output.
TPA8801B use one resister to set the transduce gain,
can provide ideal 4.56GΩ current to voltage DC gain
when the resister is 20KΩ. As the output is saturated in
the real application by offset voltage of internal amplifier,
AC coupled mode is used to remove DC offset voltage
and bias current impaction, so the real AC gain in the
application is less than ideal DC gain depend on the
capacitor values.
The internal precision amplifier has 1pA input bias
current is good to transduce down to 100pA signal,
0.4mV offset voltage to expand the input range for DC
signal, 1.3MHz GBW to meet the requirement of AC
signal which is used in some type of dust sensor
application.
TPA8801B is specified for operation over the -40° to
C
125° range.
C
TPA8801B is available in 5mm*6mm 14-lead TSSOP
package. TPA8801B possibly in 3mm*2mm 14-lead DFN
package, 1/5 size versus TSSOP-14 package, to meet
the size limitation application, the sample can be
provided in one month.
3PEAK and the 3PEAK logo are registered trademarks of
3PEAK INCORPORATED. All other trademarks are the property of
their respective owners.
Ideal DC gain when Rg=20K: 4.56GΩ
One resister(Rg) to set the gain
Supply voltage range: 2.1-5.5V
Iq: 700µA maximum
Analog output
Internal amplifier:
-
-
-
-
V
OS
: ±400µV maximum
Low noise: 25 nV/√
GBWP: 1.3MHz
Input Bias Current: 1pA typical
ESD rating: HBM 8KV / CDM 2KV
Operation temperature range: –40° to 125°
C
C
Green, Popular Type Package
Applications
Dust sensor for air quality monitoring (PM2.5,
PM10)
Photodiode interface
Sensor interface for current output sensor
Pin Configuration
TPA8801B
14-Pin TSSOP
(-T Suffixes)
TO
IN-
IN+
GND
SC1
SC2
LPFC
1
2
3
4
5
6
7
14
13
12
11
10
9
8
Out
NR
HPFC
V
CC
GR2
GR1
TP
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TPA8801B
High Sensitivity Current Input Interface
Block Diagram
2
2M Ohm
1
7
6
5
Vcc
11
3
vref
TIA
Filter
Slope
Control
Gnd
4
TP
Vout
8
Filter
9
10
12
Noise
Reduction
13
14
Rg
Pin Functions
No.
1
2
3
4
5
6
7
Mnemonic
TO
IN-
IN+
GND
SC1
SC2
LPFC
Description
TIA Output
Amplifier IN- , Sensor Input
Amplifier IN+ , Sensor Input
Ground
Slope Control Cap Input
Slope Control Cap Output
Low Pass Filter Cap
No.
8
9
10
11
12
13
14
Mnemonic
TP
GR1
GR2
V
CC
HPFC
NR
OUT
Test Point
Voltage Gain Setting
Voltage Gain Setting
Power Supply
High Pass Filter Cap
Noise Reduction
Signal Output
Description
Order Information
Model Name
TPA8801B
Order Number
TPA8801B-TR
Package
TSSOP-14
Transport Media, Quantity
Tape and Reel, 3,000
Marking
Information
TPA8801B
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TPA8801B
High Sensitivity Current Input Interface
Absolute Maximum Ratings
+
–
–
+
Note 1
Supply Voltage: V
–
V ....................................7.0V
Input Voltage............................. V
–
0.3 to V + 0.3
Input Current:
Note 2
........................................ ±10mA
Output Short-Circuit Duration
Note 3
…............
Infinite
Operating Temperature Range.......–40° to 125°
C
C
Maximum Junction Temperature................... 150°
C
Storage Temperature Range..........
–65°
to 150°
C
C
Lead Temperature (Soldering, 10 sec) ......... 260°
C
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any
Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime.
Note 2:
The inputs are protected by ESD protection diodes to each power supply. If the input extends more than 500mV beyond the power
supply, the input current should be limited to less than 10mA.
Note 3:
A heat sink may be required to keep the junction temperature below the absolute maximum. This depends on the power supply
voltage and how many amplifiers are shorted. Thermal resistance varies with the amount of PC board metal connected to the package. The
specified values are for short traces connected to the leads.
ESD, Electrostatic Discharge Protection
Symbol
HBM
MM
CDM
Parameter
Human Body Model ESD
Machine Model ESD
Charged Device Model ESD
Condition
MIL-STD-883H Method 3015.8
JEDEC-EIA/JESD22-A115
JEDEC-EIA/JESD22-C101E
Minimum Level
8
500
2
Unit
kV
V
kV
Electrical Characteristics
The specifications are at TA = 27° C. V
CC
= 5V, unless otherwise noted.
Limits
Symbol
V
CC
I
Q
TIA R
F
DG
DGE
V
REF
Internal Amplifier
GBWP
I
B
V
OS
e
N
I
SC
I
O
Gain-Bandwidth Product
Input Bias Current
Amplifier Offset Voltage
Input Voltage Noise Density
Output Short-Circuit Current
Output Current
25
100
50
1.3
1
10
400
MHz
pA
µV
nV/√
mA
mA
Parameter
Min
Power supply
Supply current
TIA Feedback Resister
Theory DC Gain
DC Gain Error
Note 1, Note 2
Note 3
Unit
Typ
390
2
228,000
-1
0.8
1
0.9
Max
5.5
700
V
µA
MΩ
V/V
%
V
2.1
Voltage Reference
Note 1: The theory loop gain is Voltage of Output = DG * Rg
Note 2: The theory DC gain is calculated exclude the V
OS
of internal amplifier, the AC gain in the real application is less
than theory DC gain, the value is depended on pass band setup.
Note 3: Guaranteed by design
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REV A
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3PEAK
Typical Application Circuit
TPA8801B
High Sensitivity Current Input Interface
Rg1 10k
C5
22pF
D1
D2
2
1
7
6
C4
C17
47nF
200pF
Used for
Low Gain Setting
U1
TPA8801B
VCC
VCC
11
C9
100nF
C8
1uF
AGND
SC2
3
IN+
8
LPFC
SC1
IN-
TO
5
TP
OUT
HPFC
NR
GR-
GR+
GND
4
14
13
12
10
P1
C10
470pF
C6
1uF
Rg
20k
C16
200pF
3PEAK
BNC
AGND
Figure 1 Typical configuration of dust detection by infrared pulse stimulation
Figure 2 Performance of dust detection by infrared pulse stimulation
9
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REV A
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TPA8801B
High Sensitivity Current Input Interface
Applications Information
Application for dust detection by infrared pulse stimulation
The Figure 1 and Figure 2 show the popular way to detect dust or PM2.5, PM10 particle by infrared pulse stimulation.
Comparing to laser solution, the infrared solution has low cost by sensor, mechanical design. The response of infrared
photodiode is very small, in 0.1nA to 1nA output, so it needs very high transduce gain to covert the signal to voltage. To
remove the DC impaction like dark current of photodiode, offset voltage and bias current of internal amplifier, the pulse
stimulation is used for the emitting diode, and the high pass filter is used in the TPA8801b.
Gain and pass band calculation of the typical application circuit for infrared
The TPA8801B tools.xlsx is a tool can calculate the circuit setting
1.
Calculate the frequency of pulse
The typical period of infrared pulse is 10ms, the typical width of the infrared pulse is 300µs. The 1/(pulse width) is
the frequency where most of energy of pulse is in, so the low pass frequency is 1/300µs = 3.3KHz.
2.
Set the gain in the pass band
Gain = DG * Rg = 4.56G when Rg = 20K, the result show TPA8801B can convert 0.22nA into 1V output
DG
228000
Rg - kΩ
20
Loop Gain - GΩ Equal input current
for 1V output - nA
4.56
0.22
Please note that the high pass filter will reduce the amplitude of response, so the calculation only give a guide to
set the gain in the real application, it should be adjusted by different sensor design including emitting diode,
photodiode, optical channel and mechanical design.
As the internal DG is 1% accuracy in full temperature range by internal matching resister, the system gain error is
decided by Rg and system level design.
3.
Set the pass band
Passband Setting, set a small value when you want to remove it
Symbol
Filter type
Value
Unit
C5
Low pass
22
pF
C4
High pass
47
nF
C17
Low pass
200
pF
C16
Low pass
200
pF
C6
High pass
1
uF
C10
Low pass
200
pF
balance from pass the pulse and block the DC signal.
Gain and pass band calculation of the application circuit for laser
f(-3dB) - kHz
3.62
1.69
7.96
39.79
0.02
16.93
Basically the configuration of typical circuit provide a pass band between 1.7KHz and 3.6KHz which can build the
Comparing to infrared, laser solution to detect dust has better resolution. The signal of laser sensor is strong and fast
than infrared sensor, so the configuration of TPA8801B must be set to smaller gain and faster bandwidth. Typical laser
pulse is about 40µs which provide 1/40µs = 25KHz.
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