ISL28107 datasheet(20/33 Pages) RENESAS

20 / 33 page

ISL28107, ISL28207, ISL28407

FN6631 Rev 8.01

Page 20 of 32

Aug 30, 2024

Applications Information

Functional Description

The ISL28107, ISL28207 and ISL28407 are single, dual and

quad, very low 1/f noise (14nV/

Hz @ 10Hz) precision op-amps.

These amplifiers feature very high open loop gain (50kV/mV) for

excellent CMRR (145dB) and gain accuracy. Both devices are

fabricated in a new precision 40V complementary bipolar DI

process.

The super-beta NPN input stage with bias current cancellation

provides bipolar-like levels of AC performance, with the low input

bias currents approaching JFET levels. The temperature

stabilization provided by bias current cancellation removes the

high input bias current temperature coefficient commonly found

in JFET amplifiers. Figures 9 and 10 show the input bias current

variation over temperature.

The input offset voltage (VOS) has a very low, worst case value of

75µV max at +25°C and a maximum TC of 0.65µV/°C. Figure 38

shows VOS as a function of supply voltage and temperature with

the common mode voltage at 0V for split supply operation.

The complementary bipolar output stage maintains stability

driving large capacitive loads (to 10nF) without external

compensation. The small signal overshoot vs. load capacitance is

shown in Figure 54.

Operating Voltage Range

The devices are designed to operate over the 4.5V (±2.25V) to

40V (±20V) range and are fully characterized at 10V (±5V) and

30V (±15V). Both DC and AC performance remain virtually

unchanged over the complete 4.5V to 40V operating voltage

range. Parameter variation with operating voltage is shown in the

“Typical Performance Curves” beginning on page 11. The input

common mode voltage range sensitivity to temperature is shown

in Figure 38 (±15V).

Input ESD Diode Protection

The input terminals (IN+ and IN-) each have internal ESD

protection diodes to the positive and negative supply rails, a series

connected 500

 current limiting resistor followed by an

anti-parallel diode pair across the input NPN transistors (Circuit 1

in “Pin Descriptions” on page 4).

The resistor-ESD diode configuration enables a wide differential

input voltage range equal to the lesser of the Maximum Supply

Voltage in the “Absolute Maximum Ratings” on page 6 (42V), or a

maximum of 0.5V beyond the V+ and V- supply voltage. The

internal protection resistors eliminate the need for external input

current limiting resistors in unity gain connections and other

circuit applications where large voltages or high slew rate signals

are present. Although the amplifier is fully protected, high input

slew rates that exceed the amplifier slew rate (±0.32V/µs) may

cause output distortion.

Output Current Limiting

The output current is internally limited to approximately ±40mA

at +25°C and can withstand a short circuit to either rail as long

as the power dissipation limits are not exceeded. This applies to

only one amplifier at a time for the dual op-amp. Continuous

operation under these conditions may degrade long-term

reliability.

Output Phase Reversal

Output phase reversal is a change of polarity in the amplifier

transfer function when the input voltage exceeds the supply

voltage. The ISL28107, ISL28207 and ISL28407 are immune to

output phase reversal, even when the input voltage is 1V beyond

the supplies.

Unused Channels

If the application only requires one channel, the user must

configure the unused channels to prevent them from oscillating.

The unused channels can oscillate if the input and output pins

are floating. This results in higher than expected supply currents

and possible noise injection into the channel being used. The

proper way to prevent this oscillation is to short the output to the

inverting input and ground the positive input, as shown in

Figure 55.

Power Dissipation

It is possible to exceed the +150°C maximum junction

temperatures under certain load and power supply conditions. It

is therefore important to calculate the maximum junction

temperature (TJMAX) for all applications to determine if power

supply voltages, load conditions, or package type need to be

modified to remain in the safe operating area. These parameters

are related using Equation 1:

Where:

•PDMAXTOTAL is the sum of the maximum power dissipation of

each amplifier in the package (PDMAX)

PDMAX for each amplifier can be calculated using Equation 2:

where:

•TMAX = Maximum ambient temperature

•

JA = Thermal resistance of the package

•PDMAX = Maximum power dissipation of one amplifier

•VS = Total supply voltage

•IqMAX = Maximum quiescent supply current of one amplifier

•VOUTMAX = Maximum output voltage swing of the application

•RL = Load resistance

FIGURE 55. PREVENTING OSCILLATIONS IN UNUSED CHANNELS

TJMAX

TMAX JAxPDMAXTOTAL

(EQ. 1)

PDMAX

VS IqMAX VS



- VOUTMAX

VOUTMAX

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



(EQ. 2)

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