MCP6V51T-ESLASHMS datasheet(23/43 Pages) MICROCHIP

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DS20006136A-page 23

MCP6V51

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. The resistors then serve as in-rush 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.

4.2.2

INTEGRATED EMI FILTER

The MCP6V51 has an integrated low-pass filter in its

inputs for the dedicated purpose of reducing any

electromagnetic or RF interference (EMI, RFI). The on-

chip filter is designed as a 2nd-order RC low-pass,

which

sets a bandwidth limit of approximately

115 MHz

and

attenuates

the

high-frequency

interference. Performance results of the MCP6V51’s

EMI rejection ratio (EMIRR) under various conditions

can be seen in Figure 2-31 and Figure 2-33.

4.2.3

RAIL-TO-RAIL OUTPUT

The Output Voltage Range of the MCP6V51 zero-drift

op amps is typically VDD - 100 mV, and VSS +50 mV

when RL =10kΩ 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 MCP6V51

amplifier 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 MCP6V51 amplifier has internal

thermal shutdown circuitry. Especially when operating

with the maximum supply voltage of 45V, observe that

the ambient temperature 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 the ambient

temperature at the device package (TA), and use

Equation 4-1 below.

EQUATION 4-1:

To derive the Power dissipation of the device, add the

terms for the devices’ quiescent power and the load

power as shown in Equation 4-2:

EQUATION 4-2:

This assumes that the device is sourcing the load

current, i.e. current flowing from the VDD supply into the

load. Use the term (IOUT ×(VOUT -VSS)) when the

device is sinking current. Note that this simple example

assumes a constant (DC) signal current flow.

The thermal shutdown circuitry activates as soon as

the junction temperature reaches approximately

+175°C causing the amplifier’s output stage to be tri-

stated (high-impedance) effectively disabling any

output current flow. The amplifier will remain in this

disabled state until the junction temperature has cooled

down to approximately +160°C. At this point the

thermal shutdown circuitry will enable the output stage

of the MCP6V51 amplifier and the device will resume

normal operation.

If a fault condition persists, for example the amplifier’s

output (VOUT) is shorted causing excessive output

current, the thermal shutdown circuity may be triggered

again and the previously described cycle repeats. This

may continue until the fault condition is removed.

It should be noted that the thermal shutdown feature of

the MCP6V51 does not guarantee that the device will

remain undamaged when operated under stress

conditions during which the device is placed into the

shutdown mode.

4.3

Application Tips

4.3.1

INPUT OFFSET VOLTAGE OVER

TEMPERATURE

Table DC Electrical Specifications gives both the

linear and quadratic temperature coefficients (TC1 and

TC2) of input offset voltage. The input offset voltage, at

any temperature in the specified range, can be

calculated as follows:

EQUATION 4-3:

PD JA TA



Where:

JA = the thermal resistance between the die

and the ambient environment, as

shown in Temperature

Specifications

VDD VSS

–

 I

IOUT

VDD VOUT

–





VOS TA



VOS TC1TTC2T

Where:

T=

TA –25°C

VOS(TA) = Input offset voltage at TA

VOS = Input offset voltage at +25°C

TC1 = Linear temperature coefficient

TC2 = Quadratic temperature coefficient

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