Datasheet

MAX4207
Precision Transimpedance Logarithmic
Amplifier with Over 5 Decades of Dynamic Range
8 _______________________________________________________________________________________
MAX4207
LOGIIN
CMVIN
V
CC
REFIIN
V
CC
CURRENT
CORRECTION
V
CC
LOGV1
SCALE
OSADJ
LOGV2
V
CC
V
CC
REFISET
CURRENT MIRROR
CMVOUTREFVOUT
REFIOUT
GND
V
EE
0.5V
1.238V
V
EE
V
EE
SUMMING
AMPLIFIER
AND
TEMPERATURE
COMPENSATION
Figure 1. Functional Diagram
PIN NAME FUNCTION
1, 9 N.C. No Connection. Not internally connected.
2
REFVOUT
1.238V Reference Voltage Output. Bypass REFVOUT to GND with a 0 to 1µF capacitor (optional).
3 GND Ground
4V
EE
Negative Power Supply. Bypass V
EE
to GND with a 0.1µF capacitor.
5 LOGV1 Logarithmic Amplifier Voltage Output 1. The output scale factor of LOGV1 is -0.25V/decade.
6 OSADJ
Offset Adjust Input. Apply a voltage at OSADJ to adjust the LOGV2 output offset voltage
(see the Output Offset section).
7 SCALE
Scale Factor Input. Adjust the output scale factor for LOGV2 using a resistive divider (see the Scale
Factor section).
8 LOGV2
Logarithmic Amplifier Voltage Output 2. Adjust the output scale factor for LOGV2 using a resistive
divider between SCALE, GND, and LOGV2 (see the Scale Factor section).
10 V
CC
Positive Power Supply. Bypass V
CC
to GND with a 0.1µF capacitor.
11 REFISET
Current Reference Adjust Input. A resistor (R
SET
), from REFISET to GND, adjusts the current at
REFIOUT (see the Adjusting the Logarithmic Intercept section).
12
CMVOUT
0V Common-Mode Voltage Reference Output
13
REFIOUT
Current Reference Output. The internal current reference output is available at REFIOUT.
14 REFIIN
Current Reference Input. Apply an external reference current at REFIIN. I
REFIIN
is the reference
current used by the logarithmic amplifier when generating LOGV1.
15 LOGIIN
Current Input to Logarithmic Amplifier. LOGIIN is typically connected to a photodiode anode or other
external current source.
16 CMVIN
Common-Mode Voltage Input. V
CMVIN
is the common-mode voltage for the input and reference
amplifiers (see the Common Mode section).
Pin Description