MAX4207 Maxim, MAX4207 Datasheet - Page 8

• Manufacturer Part Number: MAX4207
• 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 corresponding voltage output with a default -0
• Manufacturer: Maxim

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