Absolute Maximum Ratings
Absolute maximum ratings are conditions that should never be exceeded, even momentarily. For example, supplying a voltage over the maximum rating and/or using in environments outside of the temperature range may cause deterioration of IC characteristics or even damage.
This section will explain the parameters listed in the absolute maximum ratings for opamps and comparators.
Supply Voltage/Operating Voltage Range
The absolute maximum rated supply voltage is the maximum voltage that can be supplied between the positive supply (VCC) and negative supply (VEE) pins without causing characteristics degradation or damage to the internal circuit.
Here is an example of a supply voltage that can be applied to opamps/comparators with a maximum rated voltage of 36V:
The absolute maximum rated supply voltage indicates the voltage difference between the VCC and VEE pins, with the VCC-VEE values required in order to ensure that the absolute maximum rated supply voltage is not exceeded. Therefore, when supplying 24V to the VCC pin and -12V to the VEE pin, neither characteristics degradation nor damage will occur since the voltage difference is 36V.
It should be noted that there is a difference between the absolute maximum rated supply voltage and the operating supply voltage.
The absolute maximum rated supply voltage indicates the maximum supply voltage that can be supplied in a range where damage or destruction of the IC wil not occur, not a voltage range for maintaining specifications and characteristics.
In order to fully achieve the characteristics listed in the specifications, a voltage within the operating voltage range must be used.
However, please note that in some cases the absolute maximum rated supply voltage and maximum operating voltage are the same.
Differential Input Voltage
The differential input voltage is the maximum voltage that can be supplied to the +Input (Non-inverting input) and -Input (Inverting input) pins without causing damage or degrading IC characteristics.
This voltage is suitable as a reference for both the inverting and non-inverting terminals, and refers to the voltage difference between both terminals. Polarity is not important.
However, the potential of each input terminal is assumed to be equal to or greater than the potential at the VEE pin.
The reason is that an ESD protection element is built into the IC, and if the potential at the input pin is lower than VEE, current will flow from the termnial through the ESD protection element, which can lead to characteristics deterioration and/or damage.
The protection element can be connected between VEE (GND) and the input pin, as shown in the right side of the below diagram, or between the input pins and VCC and VEE (GND), providing 2 pathways.
In the former case, since there is no path for current to flow at the VCC side, the differential voltage is determined based on the withstand voltage of the transistor (NPN, PNP) connected to the input terminal, regardles of the value of VCC.
In the latter case, because a protection element exists at the VCC side as well, since the input pin requires a potential less than VCC, the differential voltage is determined by VCC-VEE or VDD-VEE.
Some opamps utilize an NPN differential input stage, and in order to provide protection between the base and emitter, a clamping diode is inserted between the input terminals, or products with a differential input voltage of several volts are used.
Common-Mode Input Voltage
The absolute maximum rating for common-mode input voltage indicates the maximum voltage that can be applied without causing degradation of IC characteristics or damage [given that the same potential is supplied to both the +Input (non-inverting input) and -Input (inverting input) pins].
The absolute maximum rated common-mode input voltage, unlike the common input voltage range listed in the electrical characteristics, does not guarantee normal IC operation.
To ensure normal IC operation, the common-mode input voltage range must be followed.
In general, the absolute maximum common-mode voltage is VEE-0.3V and VCC+0.3V, but for products without a protection element at the VCC side, voltages up to the absolute maximum rated supply voltage (i.e. VEE+36V) can be supplied, regardless of supply voltage.
In this way, the common-mode input voltage is determined by the input pin protection circuit configuration, parasitic elements, input transistor withstand voltage, and other factors.
In the case where forward voltage is supplied to the ESD protection element (diode), VEE-0.3V and VCC+0.3V indicate the voltage range where the protection element does not operate.
For differential and common mode input voltages, inputting a voltage lower than VEE-0.3V or greater than VCC+0.3V will cause current to flow through the input terminal, possibly leading to characteristics degradation and/or damage.
To prevent this, a small clamping diode can be connected to the input pin to clamp the forward voltage, or a resistor can be inserted to limit current flow to the input pin.
The first method controls the voltage input to the IC, while the second controls the current.
Please set a resistor so that the input current is less than 10mA. The VF will be at a forward voltage of approx. 0.6V.
Operating Temperature Range
The operating temperature range is a range that ensures normal operation and where expected IC functions are maintained.
Some IC characteristics vary based on temperature.
Therefore, unless otherwise specified, the values stipulated at 25C cannot be guaranteed.
There is a parameter that guarantees stable operation throughout the entire temperature range.
IC characteristics fluctuations within the operating temperature range are taken into account.
Maximum Junction Temperature/Storage Temperature Range
The maximum junction temperature is the maximum temperature the semiconductor can operate. Here, 'junction' refers to a PN junction.
If the chip temperature exceeds the maximum rated junction temperature, electron-hole pairs will be generated in the semiconductor crystal, preventing normal operation.
Therefore, thermal designs must take into account heat generation due to power consumption and ambient temperatures.
The maximum junction temperature is determined by production processes.
The storage temperature range denotes the maximum temperature during storage, when the IC is not in operation and no power is being consumed.
Normally this is equivalent to the maximum junction temperature.
Permissible Loss (Total Loss)
Permissible loss (total loss) indicates the power that the IC can consume at an ambient temperature Ta=25°C. When the IC consumes power, heat is generated, and the chip temperature will become higher than the ambient temperature.
The allowable chip temperature is determined by the maximum junction temperature, with permissible power consumption limited by the derating curves.
The internal IC chip determines the permissible loss at 25°C based on allowable temperature (maximum junction temperature) and thermal resistance of the package (heat dissipation characteristics)
The maximum junction temperature is also affected by production processes.
Heat generated from IC power consumption is dissipated by the package mold resin, lead frame, and other components.
The parameter that indicates heat dissipation characteristics is referred to as thermal resistance, and is represented by θj-a[℃/W].
This thermal resistance makes it possible to estimate the internal IC temperature.
An example of package thermal resistance is shown below. θj-a is determined by the sum of the thermal resistance θj-c between the chip and case (package) and the case and external (ambient) environment θc-a.
With a thermal resistance θj-a, ambient temperature Ta, power consumption P, the junction temperature can be calculated by the following equation.
Tj = Ta + θj-a × P [W]
Below shows the thermal derating curves.
These curves indicate the amount of power that can be consumed by the IC at different ambient temperatures without exceeding the permissible chip temperature.
As an example, let's consider the chip temperature of MSOP8.
Since the IC's storage temperature range is 55°C to 150°C, the maximum permissible chip temperature is 150°C. With a thermal resistance for MSOP8 of θj-a≒212.8℃/W, and an IC power consumption of 0.58mW, the junction temperature will be
Tj = 25[℃] + 212.8[℃/W] × 0.58[W] ≒ 150[℃]
Once the maximum permissible chip temperature is reached, no more power can be consumed. The reduced value per 1°C of the derating curves is determined from the reciprocal of the thermal resistance.
Here we show the thermal resistance of different package types. SOP8: 5.5mW/°C, SSOP-B8: 5.0mW/°C, MSOP8: 4.7mW/°C
In the above examples:
- Junction-External (Ambient) Thermal Resistance : θj-a=θj-c+θc-a[℃/W]
Where θj-c is the thermal resistance between the junction and case.
- θc-a : Thermal Resistance Between Case and External
- Ta : Ambient Temperature
- Tj : Junction Temperature
The slope of the derating curve is the reciprocal of θj-a