19-3071; Rev 0; 12/03
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
General Description
The MAX4206 logarithmic amplifier computes the log
ratio of an input current relative to a reference current
(externally or internally generated) and provides a cor-
responding voltage output with a default 0.25V/decade
scale factor. The device operates from a single +2.7V
to +11V supply or from dual ±2.7V to ±5.5V supplies
and is capable of measuring five decades of input cur-
rent across a 10nA to 1mA range.
The MAX4206’s uncommitted op amp can be used for
a variety of purposes, including filtering noise, adding
offset, and adding additional gain. A 0.5V reference is
also included to generate an optional precision current
reference using an external resistor, which adjusts the
log intercept of the MAX4206. The output-offset voltage
and the adjustable scale factor are also set using exter-
nal resistors.
The MAX4206 is available in a space-saving 16-pin thin
QFN package (4mm x 4mm x 0.8mm), and is specified
for operation over the -40°C to +85°C extended temper-
ature range.
KIT
ATION
EVALU
BLE
AVAILA
Features
♦
+2.7V to +11V Single-Supply Operation
♦
±2.7V to ±5.5V Dual-Supply Operation
♦
5 Decades of Dynamic Range (10nA to 1mA)
♦
Monotonic Over a 1nA to 1mA Range
♦
0.25V/Decade Internally Trimmed Output Scale
Factor
♦
Adjustable Output Scale Factor
♦
Adjustable Output Offset Voltage
♦
Internal 10nA to 10µA Reference Current Source
♦
0.5V Input Common-Mode Voltage
♦
Small 16-Pin Thin QFN Package (4mm x 4mm x
0.8mm)
♦
-40°C to +85°C Operating Temperature Range
♦
Evaluation Kit Available
MAX4206
Applications
Photodiode Current Monitoring
Portable Instrumentation
Medical Instrumentation
Analog Signal Processing
PART
MAX4206ETE
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 Thin QFN-EP*
*EP = Exposed Paddle.
Typical Operating Circuit
V
CC
I
IN
Pin Configuration
REFIOUT
TOP VIEW
(LEADS ON BOTTOM)
0.1µF
V
CC
LOGV2
LOGIIN
V
OUT
LOGIIN
CMVIN
REFIIN
C
COMP
R2
REFIOUT
SCALE
R1
16
15
14
13
R
COMP
REFIIN
C
COMP
R
COMP
N.C.
REFVOUT
GND
V
EE
1
2
3
4
12
11
CMVOUT
REFISET
V
CC
N.C.
MAX4206
CMVIN
CMVOUT
LOGV1
R
OS
REFISET
OSADJ
GND
V
EE
MAX4206
10
9
0.1µF
REFVOUT
0.1µF
5
LOGV1
6
OSADJ
7
SCALE
8
LOGV2
THIN QFN
R
SET
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
MAX4206
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
V
CC
.........................................................................-0.3V to +12V
V
EE
............................................................................-6V to +0.3V
Supply Voltage (V
CC
to V
EE
) .............................................. +12V
REFVOUT ....................................................(V
EE
- 0.3V) to +3.0V
OSADJ, SCALE, REFISET ...........................(V
EE
- 0.3V) to +5.5V
REFIIN, LOGIIN ........................................(V
EE
- 0.3V) to V
CMVIN
LOGV1, LOGV2, CMVOUT,
REFIOUT ......................................(V
EE
- 0.3V) to (V
CC
+ 0.3V)
CMVIN............................................................(V
EE
- 0.3V) to +1V
Continuous Current (REFIIN, LOGIIN) ................................10mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin Thin QFN (derate 16.9mW/°C above +70°C) ....1349mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature .....................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS—Single-Supply Operation
(V
CC
= +5V, V
EE
= GND = 0V, I
REF
= 1µA, I
LOG
= 10µA, LOGV2 = SCALE, LOGV1 = OSADJ, CMVIN = CMVOUT, R
SET
> 1MΩ,
T
A
= -40°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage
Supply Current
LOGIIN Current Range (Notes 3, 4)
REFIIN Current Range (Notes 3, 4)
Common-Mode Voltage
Common-Mode Voltage Input
Range
SYMBOL
V
CC
I
CC
I
LOG
I
REF
V
CMVOUT
V
CMVIN
I
REF
= 10nA,
I
LOG
= 10nA to 1mA,
K = 0.25V/decade
(Note 4)
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
T
A
= -40°C to +85°C
T
A
= +25°C, |V
CMVIN
- V
REFIIN
|,
|V
CMVIN
- V
LOGIIN
|
|V
CMVIN
- V
REFIIN
|, |V
CMVIN
- V
LOGIIN
|
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
1.218
1.195
1
490
482
500
510
518
T
A
= +25°C
T
A
= -40°C to +85°C
237.5
231.25
80
250
(Note 2)
T
A
= +25°C
T
A
= -40°C to +85°C
Minimum
Maximum
Minimum
Maximum
480
0.5
±2
500
10
1
520
1.0
±5
mV
±10
262.5
268.75
mV/
decade
µV/
decade/
°C
5
mV
µV/°C
1.258
1.275
V
mA
mV
10
1
CONDITIONS
MIN
2.7
3.9
TYP
MAX
11.0
5
7
UNITS
V
mA
nA
mA
nA
mA
mV
V
Log Conformity Error
V
LC
Logarithmic Slope (Scale Factor)
Logarithmic Slope (Scale Factor)
Temperature Drift
Input Offset Voltage
Input Offset Voltage Temperature
Drift
Voltage Reference Output
Voltage Reference Output Current
Current Reference Output Voltage
K
V
IO
V
IOS
V
REFVOUT
I
REFVOUT
V
REFISET
1
6
1.238
2
_______________________________________________________________________________________
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
DC ELECTRICAL CHARACTERISTICS—Single-Supply Operation (continued)
(V
CC
= +5V, V
EE
= GND = 0V, I
REF
= 1µA, I
LOG
= 10µA, LOGV2 = SCALE, LOGV1 = OSADJ, CMVIN = CMVOUT, R
SET
> 1MΩ,
T
A
= -40°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
LOGV2 BUFFER
Input Offset Voltage
Input Bias Current
Output Voltage Range
V
IO
I
B
V
OH
V
OL
Output Short-Circuit Current
Slew Rate
Unity-Gain Bandwidth
I
OUT+
I
OUT-
SR
GBW
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
(Note 4)
R
L
to GND = 2kΩ
R
L
to GND = 2kΩ
Sourcing
Sinking
0.2
0.01
V
CC
-
0.2
0.08
34
58
12
5
mA
V/µs
MHz
0.4
2
6
1
V
CC
-
0.3
mV
nA
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX4206
AC ELECTRICAL CHARACTERISTICS—Single-Supply Operation
(V
CC
= +5V, V
EE
= GND = 0, I
REF
= 1µA, I
LOG
= 10µA, LOGV2 = SCALE, LOGV1 = OSADJ, CMVIN = CMVOUT, R
SET
> 1MΩ,
T
A
= +25°C, unless otherwise noted.)
PARAMETER
LOGV2 Total Noise
LOGV2 Spot Noise Density
REFVOUT Total Noise
REFVOUT Spot Noise Density
REFISET Total Noise
REFISET Spot Noise Density
Small-Signal Unity-Gain
Bandwidth
SYMBOL
CONDITIONS
0.1Hz to 10Hz, total output-referred noise,
I
REF
= 10nA, I
LOG
= 100nA
f = 5kHz, I
REF
= 10nA, I
LOG
= 100nA
1Hz to 10Hz, total output-referred noise
f = 5kHz
1Hz to 10Hz, total output-referred noise
f = 5kHz
I
REF
= 1µA, I
LOG
= 10µA, R
COMP
= 300Ω,
C
COMP
= 32pF
MIN
TYP
17
0.8
3.3
266
0.67
23
1
MAX
UNITS
µV
RMS
µV/√Hz
µV
RMS
nV/√Hz
µV
RMS
nV/√Hz
MHz
DC ELECTRICAL CHARACTERISTICS—Dual-Supply Operation
(V
CC
= +5V, V
EE
= -5V, GND = 0, I
REF
= 1µA, I
LOG
= 10µA, LOGV2 = SCALE, LOGV1 = OSADJ, CMVIN = CMVOUT, R
SET
> 1MΩ,
T
A
= -40°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage (Note 2)
Supply Current
LOGIIN Current Range (Notes 3, 4)
REFIIN Current Range (Notes 3, 4)
Common-Mode Voltage
SYMBOL
V
CC
V
EE
I
CC
I
LOG
I
REF
V
CMVOUT
T
A
= +25°C
T
A
= -40°C to +85°C
Minimum
Maximum
Minimum
Maximum
480
500
10
1
520
10
1
CONDITIONS
MIN
2.7
-2.7
5
TYP
MAX
5.5
-5.5
6
7.5
UNITS
V
mA
nA
mA
nA
mA
mV
_______________________________________________________________________________________
3
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
MAX4206
DC ELECTRICAL CHARACTERISTICS—Dual-Supply Operation (continued)
(V
CC
= +5V, V
EE
= -5V, GND = 0, I
REF
= 1µA, I
LOG
= 10µA, LOGV2 = SCALE, LOGV1 = OSADJ, CMVIN = CMVOUT, R
SET
> 1MΩ,
T
A
= -40°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Common-Mode Voltage Input
Range
SYMBOL
V
CMVIN
I
REF
= 10nA,
I
LOG
= 10nA to 1mA,
K = 0.25V/decade
(Note 4)
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= -40°C to +85°C
T
A
= +25°C, |V
CMVIN
- V
REFIIN
|,
|V
CMVIN
- V
LOGIIN
|
|V
CMVIN
- V
REFIIN
|, |V
CMVIN
- V
LOGIIN
|
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
1.218
1.195
1
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
(Note 4)
R
L
to GND = 2kΩ
R
L
to GND = 2kΩ
Sourcing
Sinking
V
EE
+
0.2
0.01
V
CC
-
0.2
V
EE
+
0.08
34
58
12
5
mA
V/µs
MHz
490
482
0.4
500
510
518
2
6
1
V
CC
-
0.3
V
V
OL
Output Short-Circuit Current
Slew Rate
Unity-Gain Bandwidth
I
OUT+
I
OUT-
SR
GBW
T
A
= +25°C
T
A
= -40°C to +85°C
237.5
231.25
80
250
CONDITIONS
MIN
0.5
±2
TYP
MAX
1.0
±5
mV
±10
262.5
268.75
mV/
decade
µV/
decade/
°C
5
mV
µV/°C
1.258
1.275
V
mA
mV
UNITS
V
Log Conformity Error
V
LC
Logarithmic Slope (Scale Factor)
Logarithmic Slope (Scale Factor)
Temperature Drift
Input Offset Voltage
Input Offset Voltage
Temperature Drift
Voltage Reference Output
Voltage Reference Output
Current
Current Reference Output
Voltage
LOGV2 BUFFER
Input Offset Voltage
Input Bias Current
K
V
IO
V
IOS
V
REFVOUT
I
REFVOUT
V
REFISET
1
6
1.238
V
IO
I
B
V
OH
mV
nA
Output Voltage Range
4
_______________________________________________________________________________________
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
AC ELECTRICAL CHARACTERISTICS—Dual-Supply Operation
(V
CC
= +5V, V
EE
= -5V, GND = 0, I
REF
= 1µA, I
LOG
= 10µA, LOGV2 = SCALE, LOGV1 = OSADJ, CMVIN = CMVOUT, R
SET
> 1MΩ,
T
A
= +25°C, unless otherwise noted.)
PARAMETER
LOGV2 Total Noise
LOGV2 Spot Noise Density
REFVOUT Total Noise
REFVOUT Spot Noise Density
REFISET Total Noise
REFISET Spot Noise Density
Small-Signal Unity-Gain
Bandwidth
SYMBOL
CONDITIONS
0.1Hz to 10Hz, total output-referred noise,
I
REF
= 10nA, I
LOG
= 100nA
f = 5kHz, I
REF
= 10nA, I
LOG
= 100nA
1Hz to 10Hz, total output-referred noise
f = 5kHz
1Hz to 10Hz, total output-referred noise
f = 5kHz
I
REF
= 1µA, I
LOG
= 10µA, R
COMP
= 300Ω,
C
COMP
= 32pF
MIN
TYP
17
0.8
3.3
266
0.67
23
1
MAX
UNITS
µV
RMS
µV/√Hz
µV
RMS
nV/√Hz
µV
RMS
nV/√Hz
MHz
MAX4206
Note 1:
Note 2:
Note 3:
Note 4:
All devices are 100% production tested at T
A
= +25°C. All temperature limits are guaranteed by design.
Guaranteed and functionally verified.
Log conformity error less than ±5mV with scale factor = 0.25V/decade.
Guaranteed by design.
Typical Operating Characteristics
(V
CC
= +5V, V
EE
= GND = 0V, I
REF
= 1µA, I
LOG
= 10µA, LOGV2 = SCALE, LOGV1 = OSADJ, CMVIN = CMVOUT, R
SET
> 1MΩ,
T
A
= +25°C, unless otherwise noted.)
V
LOGV1
vs. I
LOG
MAX4206 toc01
V
LOGV1
vs. I
LOG
MAX4206 toc02
V
LOGV1
vs. I
LOG
1.50
1.25
V
LOGV1
(V)
1.00
0.75
0.50
0.25
0
-0.25
I
REF
= 10nA
T
A
= -40
°
C TO +85
°
C
V
CC
= +2.7V
V
EE
= GND
MAX4206 toc03
1.75
1.50
1.25
V
LOGV1
(V)
1.00
0.75
0.50
0.25
0
-0.25
I
REF
= 10nA
T
A
= -40
°
C TO +85
°
C
V
CC
= +5V
V
EE
= GND
1.75
1.50
1.25
V
LOGV1
(V)
1.00
0.75
0.50
0.25
0
-0.25
I
REF
= 10nA
T
A
= -40
°
C TO +85
°
C
V
CC
= +5V
V
EE
= -5V
1.75
10n
100n
1µ
10µ
I
LOG
(A)
100µ
1m
10m
1n
10n
100n
1µ
10µ 100µ
1m
10m
10n
100n
1µ
10µ
I
LOG
(A)
100µ
1m
10m
I
LOG
(A)
_______________________________________________________________________________________
5
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