Evaluates: MAX9937
7) Turn on the 12V power supply.
8) Adjust the electronic load current (I
LOAD
) between
0A and 2A and verify that V
OUT
is proportional to
V
SENSE
according to the following equation:
where V
SENSE
= I
LOAD
x R1.
Detailed Description of Hardware
The MAX9937 EV kit evaluates the MAX9937 unidirec-
tional high-side current-sense amplifier, which features a
4V to 28V input common-mode voltage range that is
independent of supply voltage (VCC = 2.7V to 5.5V).
The MAX9937 monitors the current through a current-
sense resistor by converting the sense voltage to a volt-
age output (V
OUT
). Gain is set by the ratio of an output
resistor (R2) and an input resistor (R3). High-side cur-
rent monitoring with the MAX9937 does not interfere with
the ground path of the load, making it useful for a variety
of automotive battery/ECU monitoring applications.
The MAX9937 EV kit produces an output voltage
(V
OUT
) given by the following equations:
where I
LOAD
is the current load applied to the device
and R
SENSE
is the current-sense resistor R1 (e.g.,
I
LOAD
= 2A, R
SENSE
= 0.05Ω, R2 = 20kΩ, R3 = 1kΩ,
and V
OUT
= 2V).
Overvoltage Protection
The MAX9937 EV kit provides a 1kΩ resistor at each of
the RSP and RSN inputs to demonstrate the reverse-
battery and load-dump protection capabilities of the
MAX9937 IC. The normal operating V
RSP
and V
RSN
range is 4V to 28V, but the robust input ESD structure
allows the input common-mode voltages to exceed this
range for short periods of time.
Short-duration overvoltages on the battery line (VBAT to
LOAD) are isolated from the RSP and RSN pins of the
MAX9937 by the use of input resistors R3 and R4. The
input ESD clamp structure is designed so the device
can withstand short-duration (< 1s) overvoltages up to
40V when using resistors R3 and R4 of 500Ω or greater.
The circuit can also withstand a reverse-battery voltage
of -20V. During reverse-battery conditions, size R3 and
R4 input resistors to withstand their expected power
dissipations. Refer to the
Input Common-Mode
Voltages > 28V and < 0V
section in the MAX9937 IC
data sheet for a more detailed description.
EMI Filtering
The MAX9937 EV kit provides two uninstalled capacitor
pads (C2 and C4), which the user can populate to
improve performance in the presence of input common-
mode voltage and input differential-voltage transients.
Refer to the
Flexible EMI Filtering
section in the
MAX9937 IC data sheet for a more detailed description.
