����������������������������������������������������������������� Maxim Integrated Products 9

MAX34406

Quad Current-Sense Amplifier

with Overcurrent Threshold Comparators

Efficiency and Power Dissipation

significant. Take this into consideration when choosing

the resistor value and its power dissipation (wattage)

rating. Also, the sense resistor’s value might drift if it is

device allows the use of small sense resistors to reduce

power dissipation and reduce hot spots.

Kelvin Connections

take care to eliminate parasitic trace resistance from

causing errors in the sense voltage. Either use a four-

terminal current-sense resistor or use Kelvin (force and

sense) PCB layout techniques.

Minimizing Trace Resistance

contributes to gain error in the current-sense amplifiers.

Care should be taken to minimize this resistance (shown

trace resistance can be calculated as follows:

OUTx

TRC

R

G

R1 R

=

+

For example, assume a gain of 100V/V, as in the

Then every 10mI of PCB trace resistance adds -0.01%

gain error.

Optional Output Filter Capacitor

When designing a system that uses a sample-and-hold

stage in the ADC, the sampling capacitor momentarily

loads OUTx and causes a drop in the output voltage. If

sampling time is very short (less than a microsecond),

consider using a ceramic capacitor across OUTx and

decreases the small-signal bandwidth of the current-

sense amplifier and reduces noise at OUTx.

Input Filters

Some applications of current-sense amplifiers need to

measure currents accurately even in the presence of

both differential and common-mode ripple, as well as a

wide variety of input transient conditions. For example,

high-frequency ripple at the output of a switching buck or

boost regulator results in a common-mode voltage at the

device’s inputs. Alternatively, the fast load-current tran-

sients, when measuring at the input of a switching buck

or boost regulator, can cause high-frequency differential

sense voltages to occur at the device’s inputs, although

the signal of interest is the average DC value. Such high-

frequency differential sense voltages can result in a volt-

age offset at the device output.

The device allows a method of filtering to help improve

performance in the presence of input common-mode

voltage and input differential voltage transients. Figure 2

shows a differential input filter.

filter against input differential voltages and prevents them

from reaching the device.

The corner frequency of this filter is determined by the

at INx- (R1). See Table 1 for R1 values at the different

gain options.

on the input offset voltage due to the bias current at INx-.

Figure 1. Input Trace Resistance

Figure 2. Differential Input Filter

INx+

GND

INx-

OUTx

MAX34406

LOAD

INx+

GND

INx-

OUTx

MAX34406

LOAD