FN6973 Rev.6.02

Page 13

Dec 21, 2022

ISL28005 Datasheet

5.3

Typical Application Circuit

Figure 29 shows the basic application circuit and optional protection components for switched-load applications.

For applications where the load and the power source is permanently connected, only an external sense resistor

is needed. For applications where fast transients are caused by hot plugging the source or load, external

protection components may be needed. The external current limiting resistor (RP) in Figure 29 may be required to

limit the peak current through the internal ESD diodes to < 20mA. This condition can occur in applications that

experience high levels of in-rush current causing high peak voltages that can damage the internal ESD diodes. An

RP resistor value of 100Ω provides protection for a 2V transient with the maximum of 20mA flowing through the

input while adding only an additional 13µV (worse case over-temperature) of VOS. See the following formula:

((RP x IRS-) = (100Ω x 130nA) = 13µV)

Switching applications can generate voltage spikes that can overdrive the amplifier input and drive the output of

the amplifier into the rails, resulting in a long overload recovery time. Capacitors CM and CD filter the common

mode and differential voltage spikes.

5.4

Error Sources

There are 3 dominant error sources: gain error, input offset voltage error, and Kelvin voltage error (see Figure 30).

The gain error is dominated by the internal resistance matching tolerances. The remaining errors appear as sense

voltage errors at the input to the amplifier. They are VOS of the amplifier and Kelvin voltage errors. If the transient

protection resistor is added, an additional VOS error can result from the IxR voltage due to input bias current. The

limiting resistor should only be added to the RS- input, due to the high-side gm amplifier (gmHI) sinking several

micro amps of current through the RS+ pin.

Figure 29. Typical Application Circuit

gmLO

RS-

gmHI

RS+

1.35V

OUT

GND

VCC

2.7VDC

to

28VDC

0.1VDC

to

28V DC

RS

(1mΩ to

100mΩ)

CD

RP

CM

Load

I = 2.86µA