General Description
The MAX9938 evaluation kit (EV kit) provides a proven
design to evaluate the MAX9938 high-side current-
sense amplifier, which offers precision accuracy speci-
fications of VOS less than 500µV (max) and gain error
less than 0.5% (max). This EV kit demonstrates the
MAX9938 in a tiny 1mm x 1mm x 0.6mm, 4-bump
UCSP™ package. The MAX9938 is also available in a
5-pin SOT23, but that package is not compatible with
this EV kit.
The MAX9938 EV kit PCB comes with a MAX9938FEBS+
installed, which is the 50V/V gain version. Contact the
factory for free samples of the pin-compatible
MAX9938TEBS+ and MAX9938HEBS+, which are 25V/V
and 100V/V gain versions, respectively.
Features
♦Precision Real-Time Current Monitoring
♦1.6V to 28V Input Common-Mode Range
♦Lead-Free and RoHS Compliant
♦Proven PCB Layout
♦Fully Assembled and Tested
Evaluates: MAX9938
MAX9938 Evaluation Kit
________________________________________________________________
Maxim Integrated Products
1
19-4262; Rev 0; 8/08
Component List
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Ordering Information
Component Suppliers
DESIGNATION
QTY
DESCRIPTION
C1 1
1µF ±10%, 50V X7R ceramic
capacitor (1206)
Murata GRM31MR71H105KA
C2 0 Not installed, ceramic capacitor
(0603)
R1 1
0.05Ω ±0.5%, 0.5W 4-terminal
current-sense resistor (1206)
Ohmite LVK12R050DER
DESIGNATION
QTY
DESCRIPTION
TP1, TP2 2 Test points
U1 1
Precision current-sense amplifier
(4 UCSP)
M axi m M AX 9938FE BS + ( Gai n: 50V /V )
— 1 PCB: MAX9938 Evaluation Kit+
SUPPLIER PHONE WEBSITE
Murata Electronics North America, Inc. 770-436-1300 www.murata-northamerica.com
Ohmite Mfg. Co. 866-964-6483 www.ohmite.com
PART TYPE
MAX9938EVKIT+ EV Kit
UCSP is a trademark of Maxim Integrated Products, Inc.
+
Denotes lead-free and RoHS compliant.
Note: Indicate that you are using the MAX9938 when contacting these component suppliers.
Evaluates: MAX9938
MAX9938 Evaluation Kit
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Quick Start
Recommended Equipment
Before beginning, the following equipment is needed:
• MAX9938 EV kit
• 3.6V, 1A DC power supply
• An electronic load capable of sinking 800mA (e.g.,
HP 6060B)
• Two digital voltmeters
Procedure
The MAX9938 EV kit is fully assembled and tested.
Follow the steps below to verify the board operation.
Caution: Do not turn on power supply or the elec-
tronic load until all connections are made.
1) Connect the positive terminal of the 3.6V supply to
the VBATT pad and the negative terminal of the
supply to the GND pad closest to the VBATT pad.
2) Set the electronic load to sink 800mA.
3) Connect the electronic load’s positive terminal to
the LOAD pad and the negative terminal to the
GND pad closest to the bottom of the EV kit.
4) Connect the first voltmeter across test points TP1
and TP2 to measure VSENSE.
5) Connect the second voltmeter across the VOUT
pad and the closest GND pad.
6) Turn on the power supply.
7) Turn on the electronic load.
8) Verify that the first voltmeter reading is approxi-
mately 40mV and the second voltmeter is approxi-
mately 2V.
9) Adjust the current load from 800mA to 0A and verify
that the reading of the second voltmeter is approxi-
mately 50 times the reading of the first voltmeter.
Detailed Description of Hardware
The MAX9938 evaluation kit (EV kit) provides a proven
design to evaluate the MAX9938 high-side current-
sense amplifier, which offers precision accuracy speci-
fications of VOS less than 500µV (max) and gain error
less than 0.5% (max).
Applying the VRS+ Supply and the Load
The EV kit is installed with a MAX9938FEBS+, which
has a gain of 50V/V. The current-sense resistor
(RSENSE) value is 0.05Ωwith ±0.5% tolerance. The
VOUT is given by:
VOUT =I
LOAD x RSENSE x AV
where AV is the gain and ILOAD is the current load
applied to the device.
Normal operating VRS+ and VRS- range is 1.6V to 28V.
Measuring the Load Current
The load current is measured as a voltage drop
(VSENSE) across an external sense resistor. This volt-
age is then amplified by the current-sense amplifier and
presented at the VOUT pad. Like all differential ampli-
fiers, the output voltage has two components of error
(an offset error and a gain error). The offset error affects
accuracy at low currents and the gain error affects
accuracy at large currents—both errors affect accuracy
at intermediate currents. By minimizing both offset and
gain errors, accuracy is optimized over a wide dynamic
range.
Evaluating Other Gain Versions
The MAX9938 EV kit can also be used to evaluate other
gain versions of the MAX9938 (25V/V or 100V/V, T or H
suffix, respectively). Replace U1 of the MAX9938 EV kit
with a different version of the MAX9938.
Evaluates: MAX9938
MAX9938 Evaluation Kit
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Figure 1. MAX9938 EV Kit Schematic
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
4
___________________
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Evaluates: MAX9938
MAX9938 Evaluation Kit
Figure 2. MAX9938 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX9938 EV Kit PCB Layout—Component Side
Figure 4. MAX9938 EV Kit PCB Layout—Solder Side
