19-3070; Rev 1; 6/04
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
General Description
The MAX4207 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 dual ±2.7V to
±5.5V supplies and is capable of measuring five
decades of input current across a 10nA to 1mA range.
The MAX4207’s uncommitted op amp can be used for
a variety of functions, 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 MAX4207. The output-offset voltage
and the adjustable scale factor are also set using exter-
nal resistors.
The MAX4207 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
E
BL
AVAILA
Features
♦
±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
♦
Input Amplifiers Summing Nodes at Ground
♦
Small 16-Pin Thin QFN Package (4mm x 4mm x
0.8mm)
♦
-40°C to +85°C Operating Temperature Range
♦
Evaluation Kit Available (Order MAX4206EVKIT)
MAX4207
Applications
Photodiode Current Monitoring
Portable Instrumentation
Medical Instrumentation
Analog Signal Processing
PART
MAX4207ETE
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 Thin QFN-EP*
*EP = Exposed paddle.
Typical Operating Circuit
V
CC
Pin Configuration
REFIOUT
TOP VIEW
(LEADS ON BOTTOM)
I
IN
0.1µF
V
CC
LOGV2
LOGIIN
V
OUT
LOGIIN
CMVIN
REFIIN
C
COMP
REFIOUT
R
COMP
C
COMP
REFIIN
SCALE
R2
16
15
14
13
R1
N.C.
REFVOUT
GND
V
EE
1
2
3
4
12
11
CMVOUT
REFISET
V
CC
N.C.
R
COMP
MAX4207
LOGV1
MAX4207
10
9
CMVIN
CMVOUT
REFVOUT
R3
OSADJ
V
EE
R4
V
EE
0.1µF
5
LOGV1
6
OSADJ
7
SCALE
8
LOGV2
R
SET
REFISET
GND
THIN QFN
________________________________________________________________
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
MAX4207
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
V
CC
...........................................................................-0.3V to +6V
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—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
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
V
EE
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
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
T
A
= +25°C
T
A
= -40°C to +85°C
-237.5
-231.25
80
-250
0
±2
(Note 2)
(Note 2)
T
A
= +25°C
T
A
= -40°C to +85°C
Minimum
Maximum
Minimum
Maximum
0
0.5
±5
mV
±10
-262.5
-268.75
mV/
decade
µV/
decade/
°C
5
mV
µV/°C
1.258
1.275
V
10
1
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
V
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
K
V
IO
V
IOS
V
REFVOUT
0.6
6
1.238
2
_______________________________________________________________________________________
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
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
Voltage Reference Output
Current
Current Reference Output
Voltage
LOGV2 BUFFER
Input Offset Voltage
Input Bias Current
V
IO
I
B
V
OH
Output Voltage Range
V
OL
Output Short-Circuit Current
Slew Rate
Unity-Gain Bandwidth
I
OUT+
I
OUT-
SR
GBW
R
L
to GND = 2kΩ
Sourcing
Sinking
V
EE
+
0.2
V
EE
+
0.08
34
58
12
5
mA
V/µs
MHz
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
(Note 4)
R
L
to GND = 2kΩ
0.01
V
CC
-
0.2
0.4
2
6
1
V
CC
-
0.3
V
mV
nA
SYMBOL
I
REFVOUT
V
REFISET
T
A
= +25°C
T
A
= -40°C to +85°C (Note 4)
490
482
CONDITIONS
MIN
TYP
1
500
510
518
MAX
UNITS
mA
mV
MAX4207
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
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.
_______________________________________________________________________________________
3
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
MAX4207
Typical Operating Characteristics
(V
CC
= +5V, V
EE
= -5V, 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
MAX4207 toc01
V
LOGV1
vs. I
LOG
MAX4207 toc02
V
LOGV1
vs. I
REF
1.00
0.75
V
LOGV1
(V)
0.50
0.25
0
-0.25
I
LOG
= 1µA
T
A
= -40°C TO +85°C
MAX4207 toc03
0.75
0.50
0.25
V
LOGV1
(V)
0.75
0.50
0.25
V
LOGV1
(V)
0
-0.25
-0.50
-0.75
T
A
= -40°C TO +85°C
V
CC
= +2.7V
V
EE
= -2.7V
1n
10n
100n
1µ
10µ 100µ
1m
1.25
0
-0.25
-0.50
-0.75
-1.00
T
A
= -40°C TO +85°C
-1.25
1n
10n 100n
1µ 10µ 100µ
I
LOG
(A)
1m
10m
-1.00
-1.25
-0.50
-0.75
10m
1n
10n
100n
1µ
10µ 100µ
1m
10m
I
LOG
(A)
I
REF
(A)
V
LOGV1
vs. I
LOG
MAX4207 toc04
V
LOGV1
vs. I
REF
I
LOG
= 10nA TO 1mA
1.5
1.0
ERROR (mV)
V
LOGV1
(V)
10µA
0.5
0
-0.5
-1.0
100µA
-1.5
-15
1mA
-2.0
-20
1n
10n 100n
1µ 10µ 100µ
I
REF
(A)
1m
10m
1n
10m
10nA
1m
10µA
10nA
100nA
1µA
MAX4207 toc05
NORMALIZED LOG CONFORMANCE
ERROR vs. I
LOG
15
10
5
0
-5
-10
T
A
= -40°C TO +85°C
10n 100n
1µ 10µ 100µ
I
LOG
(A)
1m
10m
T
A
= -40°C
MAX4207 toc06
2.0
1mA
1.5
100µA
1.0
V
LOGV1
(V)
0.5
0
-0.5
-1.0
-1.5
I
REF
= 10nA TO 1mA
-2.0
1n
10n 100n
1µ 10µ 100µ
I
LOG
(A)
100nA
1µA
2.0
20
NORMALIZED LOG CONFORMANCE
ERROR vs. I
LOG
MAX4207 toc07
NORMALIZED LOG CONFORMANCE
ERROR vs. I
REF
MAX4207 toc08
NORMALIZED LOG CONFORMANCE
ERROR vs. I
LOG
15
10
ERROR (mV)
5
0
-5
-10
MAX4207 toc09
20
15
10
ERROR (mV)
20
15
10
ERROR (mV)
5
0
-5
-10
-15
-20
I
LOG
= 1µA
T
A
= -40°C TO +85°C
1n
10n 100n
1µ 10µ 100µ
I
REF
(A)
1m
T
A
= -40°C
20
5
0
-5
-10
-15
-20
1n
T
A
= -40°C TO +85°C
V
CC
= +2.7V
V
EE
= -2.7V
10n 100n
1µ 10µ 100µ
I
LOG
(A)
1m
10m
T
A
= -40°C
-15
IREF = 10nA, 100nA, 1µA, 10µA, 100µA, 1mA
-20
10m
1n
10n 100n
1µ 10µ 100µ
I
LOG
(A)
1m
10m
4
_______________________________________________________________________________________
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
MAX4207
Typical Operating Characteristics (continued)
(V
CC
= +5V, V
EE
= -5V, GND = 0V, I
REF
= 1µA, I
LOG
= 10µA, LOGV2 = SCALE, LOGV1 = OSADJ, CMVIN = CMVOUT, R
SET
> 1MΩ,
T
A
= +25°C, unless otherwise noted.)
NORMALIZED LOG CONFORMANCE
ERROR vs. I
REF
MAX4207 toc10
NORMALIZED LOG CONFORMANCE
ERROR vs. I
LOG
15
10
ERROR (mV)
5
0
-5
-10
-15
-20
(V
CC
= +2.7V, V
EE
= -2.7V)
(V
CC
= +5V, V
EE
= -5V)
(V
CC
= +5.5V, V
EE
= -5.5V)
MAX4207 toc11
INPUT OFFSET VOLTAGE
(V
LOGIIN
- V
CMVIN
vs. I
LOG
)
3
2
V
LOGIIN
- V
CMVIN
(mV)
1
0
-1
-2
-3
-4
-5
MAX4207 toc12
20
ILOG = 10nA, 100nA, 1µA, 10µA, 100µA, 1mA
20
4
15
10
ERROR (mV)
5
0
-5
-10
-15
-20
1n
10n 100n
1µ 10µ 100µ
I
REF
(A)
1m
10m
1n
10n 100n
1µ 10µ 100µ
I
LOG
(A)
1m
10m
1n
10n 100n
1µ 10µ 100µ
I
LOG
(A)
1m
10m
I
LOG
PULSE RESPONSE
(I
REF
= 1µA)
MAX4207 toc13
I
REF
PULSE RESPONSE
(I
LOG
= 1µA)
MAX4207 toc14
+0.25V
0V
0V
-0.25V
-0.25V
-0.50V
-0.50V
-0.75V
20µs/div
1µA TO 100nA
0.75V
0.50V
100µA TO 1mA
10µA TO 1µA
0.50V
0.25V
10µA TO 100µA
100µA TO 10µA
0.25V
0V
1µA TO 10µA
1mA TO 100µA
0V
-0.25V
20µs/div
100nA TO 1µA
_______________________________________________________________________________________
5
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