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36V, Precision, Low-Noise,

Wide-Band Amplifier

Careful layout technique helps optimize performance

by decreasing the amount of stray capacitance at the

op amp’s inputs and outputs. To decrease stray capaci-

tance, minimize trace lengths by placing external com-

ponents close to the op amp’s pins.

For high-frequency designs, ground vias are critical to

provide a ground return path for high-frequency signals

and should be placed near the decoupling capacitors.

Signal routing should be short and direct to avoid para-

sitic effects. Avoid using right angle connectors since

they may introduce a capacitive discontinuity and ulti-

mately limit the frequency response.

Electrostatic Discharge (ESD)

The IC has built-in circuits to protect it from ESD events.

An ESD event produces a short, high-voltage pulse

that is transformed into a short current pulse once it

discharges through the device. The built-in protection

circuit provides a current path around the op amp that

prevents it from being damaged. The energy absorbed

by the protection circuit is dissipated as heat.

ESD protection is guaranteed up to Q8kV with the Human

Body Model (HBM). The Human Body Model simulates

the ESD phenomenon wherein a charged body directly

transfers its accumulated electrostatic charge to the

ESD-sensitive device. A common example of this phe-

nomenon is when a person accumulates static charge

by walking across a carpet and then transfers all of the

charge to an ESD-sensitive device by touching it.

Not all ESD events involve the transfer of charge into the

device. ESD from a charged device to another body is

also a common form of ESD.

If a charged device comes into contact with another

conductive body that is at a lower potential, it discharges

into that body. Such an ESD event is known as Charged

Device Model (CDM) ESD, which can be even more

destructive than HBM ESD (despite its shorter pulse

duration) because of its high current. The IC guarantees

CDM ESD protection up to Q1kV.

Driving High-Resolution Sigma-Delta ADCs

The MAX9632’s excellent AC specifications and 55MHz

bandwidth are a good fit for driving high-speed, precision

delta-sigma ADCs. These ADCs require an ultra-low noise

op amp to achieve signal-to-noise ratios (SNR) better than

100dB. The MAX11040 is a 24-bit, 4-channel, simultane-

ous-sampling ADC with 117dB SNR at 1ksps and 106dB

at 16ksps. The MAX11040 measures analog inputs up to

Q

2.2V. Sampling up to 64ksps, the MAX11040 achieves

better than -94dB THD and 94dB SFDR.

The MAX11040 measures four differential inputs simulta-

neously, outputting the data through an SPI™ interface

to allow daisy-chaining the data outputs and inputs

together. Therefore, up to eight MAX11040 devices can

be placed in parallel to measure up to 32 inputs simulta-

neously. This is ideal for 3-phase power monitoring that

requires multiple current and voltage readings and very

wide dynamic range.

The Typical Application Circuit shows an example of the

MAX9632 driving the MAX11040.

Chip Information

PROCESS: BiCMOS

SPI is a trademark of Mototrola, Inc.