MAX44252 Maxim, MAX44252 Datasheet - Page 10

• Manufacturer Part Number: MAX44252
• Description: The MAX44251/MAX44252 are 20V, ultra-precision, low-noise, low-drift amplifiers that offer near-zero DC offset and drift through the use of patented autocorrelating zeroing techniques
• Manufacturer: Maxim

The MAX44251/MAX44252 are high-precision amplifiers
that have less than 3FV of typical input-referred offset
and low flicker noise. These characteristics are achieved
through an autozeroing technique that samples and finds
repeating patterns of signal to cancel the input offset volt-
age and 1/f noise of the amplifier.
The ICs feature an autozero circuit that allows the devices
to achieve less than 6FV (max) of input offset voltage at
room temperature and eliminate the 1/f noise.
Flicker noise, inherent in all active devices, is inversely
proportional to frequency presented. 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.
Electromagnetic interference (EMI) noise occurs at high-
er frequency that results in malfunction or degradation of
electrical equipment.
The ICs have an input EMI filter to avoid the output get-
ting affected by radio frequency interference. The EMI
filter composed of passive devices presents significant
higher impedance to higher frequency.
The ICs feature 1.15mA current consumption per channel
and a voltage supply range from either 2.7V to 20V single
supply or ±1.35V to ±10V split supply.
Figure 1. Weight Scale Application Circuit
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20V
High Supply Voltage Range
20V, Ultra-Precision, Low-Noise Op Amps
Detailed Description
R
G
BUFFER
BUFFER
Noise Suppression
50R
50R
20V
20V
G
G
MAX44251
MAX44251
R
R
Autozero
R
1.5V
MAX44251
BUFFER
R
20V
The ICs are ultra-high-precision operational amplifiers with
a high supply voltage range designed for load cell, medi-
cal instrumentation and precision instrument applications.
These devices are also designed to interface with pres-
sure transducers and are ideal for precision weight scale
application as shown in Figure 1.
The MAX44251/MAX44252's low input offset voltage, low
noise, and fast settling time make these amplifiers ideal
for ADC buffers. Weigh scales are one application that
often require a low-noise, high-voltage amplifier in front
of an ADC. Figure 1 details an example of a load cell and
amplifier driven from the same Q10V supplies, along with
the MAX11211 18-bit delta sigma ADC. Load cells pro-
duce a very small voltage change at their outputs, there-
fore driving the excitation source with a higher voltage
produces a wider dynamic range that can be measured
at the ADC inputs.
The MAX11211 ADC operates from a single 2.7V to 3.6V
analog supply, offers 18-bit noise-free resolution and
0.86mW power dissipation. The MAX11211 also offers
> 100dB rejection at 50Hz and 60Hz. This ADC is part of
a family of 16-, 18-, 20-, and 24-bit delta sigma ADCs with
high precision and < 1mW power dissipation.
The MAX44251/MAX44252's low input offset voltage and
low noise allow a gain circuit prior to the MAX11211 with-
out losing any dynamic range at the ADC.
V
V
IN+
IN-
MAX11211
MAX44251/MAX44252
V
V
DD
SS
OUTPUT
V
REF
Applications Information
C
1
R
1
3V
V
OUT
MAX6126
ADC Buffer Amplifier
PROCESSOR
MICRO-
3.3V
V
DD