MAX4208EVKIT+ Maxim Integrated Products, MAX4208EVKIT+ Datasheet - Page 11

• Manufacturer Part Number: MAX4208EVKIT+
• Description: KIT EVAL FOR MAX4208
• Manufacturer: Maxim Integrated Products

Specifications of MAX4208EVKIT+

• Channels Per Ic: 1 - Single
• Amplifier Type: Instrumentation
• Output Type: Single-Ended, Rail-to-Rail
• Slew Rate: 0.08 V/µs
• Current - Output / Channel: 25mA
• Operating Temperature: -40°C ~ 125°C
• Current - Supply (main Ic): 1.4mA
• Voltage - Supply, Single/dual (±): 2.85 V ~ 5.5 V, ±1.425 V ~ 2.25 V
• Board Type: Fully Populated
• Utilized Ic / Part: MAX4208, MAX4209
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -

The MAX4208/MAX4209 family of instrumentation ampli-
fiers implements a spread-spectrum, autozeroing tech-
nique that minimizes the input offset error, drift over time
and temperature, and the effect of 1/f noise. Unlike the
traditional three-op amp instrumentation amplifier, this
technique allows true ground-sensing capability com-
bined with a low input bias current and increased com-
mon-mode rejection.
The differential input signal is converted to a current by
an input transconductance stage. An output transcon-
ductance stage converts a portion of the output voltage
(equal to the output voltage divided by the gain) into
another precision current. These two currents are sub-
tracted and the result is fed to a loop amplifier with suffi-
cient gain to minimize errors (Figures 1 and 2). The
MAX4209 has a factory-trimmed gain of 100V/V. The
MAX4208 has an adjustable gain, set with an external
pair of resistors between OUT, FB, and REF (Figure 1).
The MAX4208/MAX4209 have an output reference input
(REF) that is connected to an external reference for bipo-
lar operation of the device. For single-supply operation,
the range for V
put-swing capability and maximum symmetrical dynamic
range is obtained at REF = V
ting depends on the supply voltage and output-voltage
Figure 1. MAX4208 Functional Diagram
IN+
G = 1 +
IN-
R2
R1
MAX4208
g
m
Instrumentation Amplifiers with REF Buffer
REF
______________________________________________________________________________________
is 0V to (V
AMP
Detailed Description
V
V
DD
SS
g
m
DD
DD
/2, the optimal V
- 1.3V). Although full out-
SHDN
+1
Ultra-Low Offset/Drift, Precision
R2
R1
OUT
FB
REF
REFIN/MODE
REF
set-
swing needed by the application. The maximum recom-
mended differential input voltage is ±100mV. Linearity
and accuracy are degraded above that level. The
MAX4208/MAX4209 operate with single 2.85V to 5.5V
supply voltages or dual ±1.425V to ±2.75V supplies.
The MAX4208/MAX4209 have a shutdown feature to
reduce the supply current to 1.4µA (typ) when REFIN/
MODE is connected to V
In a single-supply system, bipolar operation of an
instrumentation amplifier requires the application of a
voltage reference (REF) to set the output voltage level
when a zero differential voltage is applied to the input.
The output swing is around this reference level, which
is usually set to half of the supply voltage for the largest
swing and dynamic range.
In many instrumentation amplifiers, the gain-setting
resistors as well as the R
and REF. OUT can sink and source current but the
need for REF to sink and source current is often over-
looked and can lead to significant errors. Therefore, the
MAX4208/MAX4209 include a REFIN buffer, an internal,
precision unity-gain buffer on-chip to sink and source the
currents needed at REF without loading the reference
voltage supplied at REFIN/MODE.
Figure 2. MAX4209 Functional Diagram
G = 1 +
IN+
IN-
REF, REFIN/MODE, and Internal REFIN
R2
R1
MAX4209
g
m
Buffer of the MAX4208/MAX4209
AMP
DD
L
V
V
DD
SS
are connected between OUT
.
g
m
R2
R1
SHDN
+1
OUT
FB
REF
REFIN/MODE
11