MAX44246
36V, Low-Noise, Precision, Dual Op Amp
Pin Configuration
TOP VIEW
+
OUTA
INA-
INA+
GND
1
2
3
4
8
7
6
5
V
DD
MAX44246
OUTB
INB-
INB+
µMAX/SO
Pin Description
PIN
1
NAME
OUTA
INA-
FUNCTION
Channel-A Output
2
Channel-A Negative Input
Channel-A Positive Input
Negative Supply Voltage
Channel-B Positive Input
Channel-B Negative Input
Channel-B Output
3
INA+
GND
INB+
INB-
4
ꢀ
6
7
OUTB
ꢁ
V
Positive Supply Voltage
DD
The 1/f noise appears as a slow varying offset voltage and
is eliminated by the chopping technique used.
Detailed Description
The MAX44246 is a high-precision amplifier that provides
below ꢀµV of maximum input-referred offset and low
flicker noise. These characteristics are achieved by using
a combination of proprietary auto-zeroing and chopper
stabilized techniques. This combination of auto-zeroing
and chopping ensures that these amplifiers give all the
benefits of zero-drift amplifiers, while still ensuring low
noise, minimizing chopper spikes, and providing wide
bandwidth. Offset voltages due to power ripple/spikes as
well as common-mode variation, are corrected resulting
in excellent PSRR and CMRR specifications.
Electromagnetic interference (EMI) noise occurs at higher
frequency, resulting in malfunction or degradation of elec-
trical equipment. The ICs have an input EMI filter to avoid
the output being affected by radio frequency interference.
The EMI filter composed of passive devices, presents sig-
nificant higher impedance to higher frequency.
Applications Information
ADC Buffer Amplifier
The MAX44246 has low input offset voltage, low noise,
and fast settling time that make this amplifier ideal for
ADC buffers. Weight scales are one application that often
requires a low-noise, high-voltage amplifier in front of an
ADC. The Typical Operating Circuit details an example
of a load cell and amplifier driven from the same 1ꢂV
supplies, along with the MAX11211 1ꢁ-bit delta sigma
ADC. Load cells produce a very small voltage change at
their outputs; therefore driving the excitation source with a
higher voltage produces a wider dynamic range that can
be measured at the ADC inputs.
Noise Suppression
Flicker noise, inherent in all active devices, is inverse-
ly proportional to frequency present. Charges at the
oxide-silicon interface that are trapped-and-released
by MOSFET oxide occurs at low frequency more often.
For this reason, flicker noise is also called 1/f noise. The
MAX44246 eliminates the 1/f noise internally, thus making
it an ideal choice for DC or sub-Hz precision applications.
Maxim Integrated
9
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