MCP6V51T-ESLASHMS datasheet(23/50 Pages) MICROCHIP

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DS20006136B-page 23

MCP6V51/2/4

Figure 4-6 shows one approach of protecting the inputs

against Overvoltage conditions with external diodes.

The device marked as DExt may be small-signal silicon

diodes, or Schottky diodes, for lower clamping

voltages, or diode connected FETs for low leakage.

Depending on the application, the additional diode

capacitance should be considered.

FIGURE 4-6:

Protecting the Analog Inputs

Against High Voltages.

A current limit resistor (RLimit) may be needed to

prevent excessive current flow through the external

diodes (DExt). If the amplifier inputs will be subjected to

Overvoltage conditions as part of the application, an

additional resistor (RIN) in series with the vulnerable

input pin (here VIN+) may be needed to limit the Fault

current to a safe level (e.g., 2 mA).

4.2.1.3

Input Current Limits

In order to prevent damage and/or improper operation of

these amplifiers, the circuit must limit the currents into the

input pins (see

Section 1.1 “Absolute Maximum

Ratings†”). This requirement is independent of the

voltage limits discussed previously. Figure 4-7 shows

one approach to protecting these inputs. The R1 and R2

resistors limit the possible current in or out of the input

pins (and into D1 and D2).

FIGURE 4-7:

Protecting the Analog Inputs

Against High Currents.

It is also possible to connect the diodes to the left of the

R1 and R2 resistors. In this case, the currents through

the D1 and D2 diodes need to be limited by some other

mechanism (see Figure 4-6). The resistors then serve

as inrush current limiters; the DC current into the input

pins (VIN+ and VIN-) should be very small.

A significant amount of current can flow out of the

inputs (through the ESD diodes) when the Common-

Mode Voltage (VCM) is below ground (VSS). See

Figure 2-16 for further details.

4.2.2

INTEGRATED EMI FILTER

The MCP6V5X op amps have an integrated low-pass

filter in their inputs for the dedicated purpose of

reducing any Electromagnetic or RF Interference (EMI,

RFI). The on-chip filter is designed as a second-order

RC low-pass, which sets a bandwidth limit of

approximately 115 MHz and attenuates the high-

frequency interference. Performance results of the

MCP6V51/2/4 devices’ EMI Rejection Ratio (EMIRR)

under various conditions can be seen in Figure 2-31.

4.2.3

RAIL-TO-RAIL OUTPUT

The output voltage range of the MCP6V51/2/4

zero-drift op amps is typically VDD – 100 mV and

VSS + 50 mV when RL = 10 kΩ is connected to VDD/2

and VDD = 45V. Refer to Figure 2-18, Figure 2-19 and

Figure 2-20 for more information.

4.2.4

THERMAL SHUTDOWN

Under certain operating conditions, the MCP6V5X ampli-

fier can be subjected to a rise of its die temperature

above the specified maximum junction temperature of

+150°C. To control possible overheating and damage,

the MCP6V5X amplifier has internal thermal shutdown

circuitry. Especially when operating with the maximum

supply voltage of 45V, observe that the ambient tempera-

ture and/or the amplifier’s output current are such that the

junction temperature remains below the specified limit.

To estimate the Junction Temperature (TJ), consider

these factors: the total Power Dissipation of the device

(PD) and theAmbient Temperature at the device package

(TA), and use Equation 4-1 below.

EQUATION 4-1:

VDD

VOUT

MCP6V5X

–

min(R1 R2



VSS min V1 V2







–

5 mA

--------------------------------------------



min(R1 R2



max V1 V2







VDD

–

5 mA

------------------------------------------------



PD JA TA



Where:

JA = The thermal resistance between the die

and the ambient environment, as shown

in Temperature Specifications

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