ISL28114, ISL28214, ISL28414

FN6800 Rev 10.00

Page 9 of 23

December 8, 2016

Applications Information

Functional Description

The ISL28114, ISL28214 and ISL28414 are single, dual, and

quad, CMOS rail-to-rail input, output (RRIO) micropower

operational amplifiers. They are designed to operate from single

supply (1.8V to 5.5V) or dual supply (±0.9V to ±2.75V). The parts

have an input common-mode range that extends 100mV above

and below the power supply voltage rails. The output stage can

swing to within 15mV of the supply rails with a 10kΩ load.

Input ESD Diode Protection

All input terminals have internal ESD protection diodes to both

positive and negative supply rails, limiting the input voltage to

within one diode beyond the supply rails. For applications where

the input differential voltage is expected to exceed 0.5V, an

external series resistor must be used to ensure the input currents

never exceed 20mA (see Figure 19).

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 ISL28114, ISL28214, and ISL28414 are immune to

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

the supplies.

Unused Channels

If the application requires less than all amplifiers on one

channel, the user must configure the unused channel(s) to

prevent oscillation. The unused channel(s) will oscillate if the

input and output pins are floating. This will result 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 20).

Power Dissipation

It is possible to exceed the +125°C maximum junction

temperatures under certain load, power supply conditions, and

ambient temperature conditions. It is therefore important to

applications to determine if power supply voltages, load

conditions, or package types need to be modified to remain in

the safe operating area. These parameters are related using

Equation 1:

where:

where:

•

ISL28114, ISL28214, and ISL28414 SPICE

Model

Figure 21 on page 11 shows the SPICE model schematic and

Figure 22 on page 12 shows the net list for the SPICE model. The

model is a simplified version of the actual device and simulates

important AC and DC parameters. AC parameters incorporated

into the model are: 1/f and flatband noise, Slew Rate, CMRR, Gain,

and Phase. The DC parameters are IOS, total supply current, and

output voltage swing. The model uses typical parameters given in

the “Electrical Specifications” Table beginning on page 4. The

AVOL is adjusted for 90dB with the dominate pole at 125Hz. The

CMRR is set 72dB, f = 80kHz. The input stage models the actual

device to present an accurate AC representation. The model is

configured for ambient temperature of +25°C.

Figures 23 through 30 show the characterization vs simulation

results for the Noise Voltage, Closed Loop Gain vs Frequency,

Large Signal 5V Step Response, and CMRR and Open-Loop Gain

Phase.

FIGURE 19. INPUT ESD DIODE CURRENT LIMITING

-

+

V+

V-

FIGURE 20. PREVENTING OSCILLATIONS IN UNUSED CHANNELS

-

+

+

=

(EQ. 1)



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



+



=

(EQ. 2)