Data Sheet

MAX74810

analog.com

Rev. 0

19 of 23

The EMI filter is composed of two 200Ω input series resistors (RS1 and RS2), two common-mode capacitors (CCM1 and

CCM2), and a differential capacitor (CDM). These RC networks set the −3dB low-pass cutoff frequencies at 50MHz for

common-mode signals, and at 33MHz for differential signals. After the EMI filter, back-to-back diodes (D5 and D6) are

added to protect internal circuit devices from high voltage input transients. Each diode has about 1V of forward turn-

on voltage.

As specified in the Absolute Maximum Ratings section (see Table 3), the maximum input differential voltage is limited

to ±5V. If more than ±5V is applied, a continuous current larger than ±10mA flows through one of the back-to-back

diodes. This current compromises long-term reliability and can cause permanent damage to the device.

Figure 52. Input EMI Filter and Clamp Circuit

Thermal Shutdown

As soon as the junction temperature reaches 190°C, the thermal shutdown circuitry shuts down the amplifier. Note

that either one of the two thermal shutdown circuitries is activated; this activation disables the channel. When the

amplifier is disabled, the output becomes open state and the quiescent current of the channel decreases to 0.1mA.

When the junction temperature cools down to 160°C, the thermal shutdown circuitry enables the amplifier and the

quiescent current increases to its typical value.

When overheating in the die is caused by an undesirable excess amount of output current, the thermal shutdown

circuit repeats its function. The junction temperature keeps increasing until it reaches 190°C and one of the channels

is disabled. Then, the junction temperature cools down until it reaches 160°C, and the channel is enabled again. The

process then repeats.

Input Protection

When the input of the MAX74810 exceeds one of the supply rails by more than 300mV, the ESD diodes mentioned in

the On-Chip Input EMI Filter and Clamp Circuit section become forward-biased and large amounts of current begin to

flow through them. Without current limiting, this excessive fault current causes permanent damage to the device. If

the inputs are expected to be subject to overvoltage conditions, insert a resistor in series with each input to limit the

input current to ±10 mA maximum. However, consider the resistor thermal noise effect on the entire circuit.

At a ±25V supply voltage, the broadband voltage noise of the MAX74810 is approximately 5.8nV/√Hz (at unity gain),

and a 1kΩ resistor has a thermal noise of 4nV/√Hz. Adding a 1kΩ resistor increases the total noise to 7nV/√Hz.

Noise Considerations

1/f Noise

1/f noise, also known as pink noise or flicker noise, is inherent in semiconductor devices and increases as frequency

decreases. At a low frequency, 1/f noise is a major noise contributor and causes a significant output voltage offset

when amplified by the noise gain of the circuit. However, because the low frequency 1/f noise appears as a slow

varying offset to the MAX74810, it is effectively reduced by the chopping technique. This technique allows the

MAX74810 to have a much lower noise at DC and low frequency in comparison to standard low noise amplifiers that

are susceptible to 1/f noise. Figure 46 shows the 0.1Hz to 10Hz noise to be only 117nV p-p of noise.

V+

+IN x

–IN x

V–

RS1

200Ω

RS2

200Ω

D1

D2

D5

D6

D4

D3

CCM1

CDM

CCM2