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ACF2101
Low Noise, Dual
SWITCHED INTEGRATOR
A B
A B
V+ Gnd V
Sw In B
Hold
Sw In A
Cap A
In A
Com A
Sw Com A
Sw Out A
Out A
100pF
Cap B
In B
Com B
Sw Com B
Sw Out B
Out B
A
B
Reset
Hold
Select
100pF
A B
A B
Hold
Reset
Reset
Select
Select
C
INTERNAL
C
INTERNAL
APPLICATIONS
q
CURRENT TO VOLTAGE CONVERSION
q
PHOTODIODE INTEGRATOR
q
CURRENT MEASUREMENT
q
CHARGE MEASUREMENT
q
CT SCANNER FRONT END
q
MEDICAL, SCIENTIFIC, AND INDUSTRIAL
INSTRUMENTATION
DESCRIPTION
The ACF2101 is a dual switched integrator for preci-
sion applications. Each channel can convert an input
current to an output voltage by integration, using either
an internal or external capacitor. Included on the chip
are precision 100pF integration capacitors, hold and
reset switches, and output multiplexers.
As a complete circuit on a single chip, the ACF2101
eliminates many of the problems commonly encoun-
tered in discrete designs, such as leakage current errors
and noise pickup. The integrating approach can pro-
vide lower noise than conventional transimpedance
amplifier designs and also eliminates the need for high
performance, high value feedback resistors.
The extremely low bias current and low noise of the
ACF2101's
Difet
amplifiers, along with active la-
ser trimming of both offset and drift, assure precision
current to voltage conversion.
Although designed for +5V, 15V supplies, the
ACF2101 can be operated on supplies up to
18VDC.
It is available in both 24-pin plastic DIP and SOIC
packages.
Difet
Burr-Brown Corp.
FEATURES
q
INCLUDES INTEGRATION CAPACITOR,
RESET AND HOLD SWITCHES, AND
OUTPUT MULTIPLEXER
q
LOW NOISE: 10
Vrms
q
LOW CHARGE TRANSFER: 0.1pC
q
WIDE DYNAMIC RANGE: 120dB
q
LOW BIAS CURRENT: 100fA
FPO
1990 Burr-Brown Corporation
PDS-1078D
Printed in U.S.A. September, 1994
ACF2101
2
V
OUT
=
I
IN
dt
SPECIFICATIONS
ELECTRICAL
At T
A
= +25
C, V+ = +5V, V = 15V, Internal C
INTEGRATION
= C
INTERNAL
= 100pF, unless otherwise noted.
C
INTEGRATION
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
1
ACF2101BP, BU
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ANALOG INPUT
INPUT RANGE
Input Current Range
Switched Input (S
W
I
N
A, S
W
I
N
B)
100
A
Direct Input (I
N
A, I
N
B)
100
A
INPUT IMPEDANCE
Switched Input
Hold Switch OFF
1000
G
Hold Switch ON
1.5
k
Direct Input
Virtual Ground
HOLD SWITCH VOLTAGE
Hold Switch Withstand Voltage
Hold Switch OFF
10
+0.5
V
OFFSET VOLTAGE
Input Offset Voltage
0.5
2
mV
Average Drift
1
5
V/
C
DIGITAL INPUTS
Logic Family
TTL Compatible
V
IH
(Logic 1 = Switch OFF)
2
5.5
V
V
IL
(Logic 0 = Switch ON)
0.5
0.8
V
I
IH
V
IH
= +5V
2
A
I
IL
V
IL
= 0V
0
A
Switching Speed (All Switches)
Switch ON
200
ns
Switch OFF
200
ns
TRANSFER CHARACTERISTICS
TRANSFER FUNCTION
V
DYNAMIC CHARACTERISTICS
Integrate Mode
Slew Rate
1
3
V/
s
Reset Mode
Slew Rate
3
V/
s
Settling Time to 0.01%FSR
(1)
10V Step
5
10
s
Overload Recovery
Positive or Negative
5
s
Output Multiplexer (Select Switches)
Settling Time to 0.01%FSR
C
LOAD
< 1000pF
6.5
s
Settling Time to 0.01%FSR
C
LOAD
< 100pF
2
s
INTEGRATION CAPACITOR (C
INTERNAL
)
Internal Capacitor
Value
100
pF
Accuracy
0.5
2
%
Temperature Coefficient
50
25
0
ppm/
C
Memory
30
100
ppm of FSR
RESET SWITCH
Impedance
Reset OFF
1000
G
Reset ON
1.5
k
MODES OF OPERATION
Switch
Hold
Reset
Integrate Mode
ON
OFF
Hold Mode
OFF
OFF
Reset Mode
ON/OFF
ON
(Logic 1 = OFF, Logic 0 = ON)
ACF2101
3
SPECIFICATIONS
(CONT)
At T
A
= +25
C, V+ = +5V, V = 15V, Internal C
INTEGRATION
= C
INTERNAL
= 100pF, unless otherwise noted.
ACF2101BP, BU
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
OUTPUT
Voltage Output Range (All Outputs)
10
13.5, +1.0
+0.5
V
Current Output, Direct Output (Out A, Out B)
5
mA
Short Circuit Current
Direct Output
25
mA
Switched Output (Sw Out A, Sw Out B)
2
8
mA
Select Switch Withstand Voltage
Switched Output
10
+0.5
V
Switched Common (Sw Com A, Sw Com B)
0.5
+0.5
V
Output Impedance
Direct Output
0.1
Switched Output
Select Switch ON
250
||
5
|| pF
Select Switch OFF
1000 || 4
G
|| pF
Leakage Current
Select Switch OFF
10
100
pA
Load Capacitance Stability
Direct Output
500
pF
Switched Output
Any
pF
OUTPUT ACCURACY
Nonlinearity
0.005
0.01
%FSR
Channel Separation
80
dB
Op Amp Bias Current
Value
100
1000
fA
Temperature Coefficient
Doubles Each +10
C
Hold Mode Droop
1
10
nV/
s
Integrate Mode Droop
1
10
nV/
s
Voltage Offset
(2)
Value
3
mV
Temperature Coefficient
5
V/
C
Power Supply Rejection
V
S
= +4.5V to +18V, 10V to 18V
80
100
dB
OUTPUT NOISE
Total Output Noise
(3)
BW = 0.1Hz to 10Hz
2
Vrms
Integrate Mode
(4)
BW = 0.1Hz to 250kHz
10(1 + C
IN
/C
INTEGRATION
)
Vrms
Hold Mode
BW = 0.1Hz to 250kHz
10
Vrms
Reset Mode
BW = 0.1Hz to 250kHz
10
Vrms
CHARGE TRANSFER ERRORS
(5)
Reset to Integrate Mode
(6)
Charge Transfer
0.1
0.5
pC
Charge Transfer TC
0.2
fC/
C
Charge Offset Error
1
5
mV
Charge Offset TC
2
V/
C
Integrate to Hold Mode
C
IN
> 50pF
Charge Transfer
0.2
1
pC
Charge Transfer TC
0.4
fC/
C
Charge Offset Error
2
10
mV
Charge Offset TC
4
V/
C
Hold to Integrate Mode
C
IN
> 50pF
Charge Transfer
0.2
1
pC
Charge Transfer TC
0.4
fC/
C
Charge Offset Error
2
10
mV
Charge Offset TC
4
V/
C
POWER SUPPLY
Specified Operating Voltage
+5, 15
V
Operating Voltage Range
Positive Supply
+4.5
+18
V
Negative Supply
10
18
V
Current
Positive Supply
For Dual
12
15
mA
Negative Supply
For Dual
3.5
5.2
mA
TEMPERATURE RANGE
Specification
40
+85
C
Operation
40
+125
C
Storage
40
+125
C
Thermal Resistance (both packages)
Junction to Ambient
100
C/W
NOTES: (1) FSR is Full Scale Range = 10V (0 to 10V). (2) Includes offset errors from all modes of operation. (3) Total noise is rms total of noise for the modes
of operation used. (4) C
IN
= capacitance of sensor connected to ACF2101 input; C
INTERGRATION
= integration capacitance = C
INTERNAL
+ C
EXTERNAL
. (5) Errors created
when the internal switches are driven from one mode to another. (6) The charge transfer is 0.1pC; for an integration capacitance of 100pF, the resultant charge
offset voltage error is 1mV.
ACF2101
4
ABSOLUTE MAXIMUM RATINGS
Supply ...............................................................................................
18V
Input Current .....................................................................................
5mA
Output Short Circuit Duration .................................. Continuous to Ground
Power Dissipation .......................................................................... 500mW
Operating Temperature ................................................... 40
C to +125
C
Storage Temperature ...................................................... 40
C to +125
C
Junction Temperature .................................................................... +150
C
Lead Temperature (soldering, 10s) ................................................ +300
C
ELECTROSTATIC
DISCHARGE SENSITIVITY
Electrostatic discharge can cause damage ranging from per-
formance degradation to complete device failure. Burr-
Brown Corporation recommends that all integrated circuits
be handled and stored using appropriate ESD protection
methods.
PACKAGE
DRAWING
TEMPERATURE
PRODUCT
PACKAGE
NUMBER
(1)
RANGE
ACF2101BP
24-Pin Plastic DIP
243
40
C to +85
C
ACF2101BU
24-Pin Plastic SOIC
239
40
C to +85
C
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix C of Burr-Brown IC Data Book.
PACKAGE/ORDERING INFORMATION
TOP VIEW
ACF2101BU
PIN CONFIGURATION
DIP and SOIC package have different pinouts.
TOP VIEW
ACF2101BP
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
DIP
Out A
Gnd A
Com A
Cap A
In A
Sw In A
Sw In B
In B
Cap B
Com B
Gnd B
Out B
Sw Out A
Sw Com A
Select A
Reset A
Hold A
V+
V
Hold B
Reset B
Select B
Sw Com B
Sw Out B
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
Sw In B
In B
Cap B
Com B
Gnd B
Out B
Sw Out B
Sw Com B
Select B
Reset B
Hold B
V
Sw In A
In A
Cap A
Com A
Gnd A
Out A
Sw Out A
Sw Com A
Select A
Reset A
Hold A
V+
SOIC
ACF2101
5
PAD
FUNCTION
13
B Switch-Out
14
B Switch-Common
15
B Select
16
B Reset
17
B Hold
18
V
19
V+
20
A Hold
21
A Reset
22
A Select
23
A Switch-Common
24
A Switch-Out
DICE INFORMATION
PAD
FUNCTION
1
A Out
2
A Ground
3
A Common
4
A Cap
5
A In
6
A Switch-In
7
B Switch-In
8
B In
9
B Cap
10
B Common
11
B Ground
12
B Out
Substrate Bias: Ground.
MECHANICAL INFORMATION
MILS (0.001")
MILLIMETERS
Die Size
132 x 157
5
3.35 x 3.99
0.13
Die Thickness
20
3
0.51
0.08
Min. Pad Size
4 x 4
0.10 x 0.10
Backing
None
ACF2101 DIE TOPOGRAPHY
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