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Evaluates: MAX49921

MAX49921 Evaluation Kit

Detailed Description of Hardware

The MAX49921 EV kit provides a proven design to evalu-

ate the MAX49921 high-side, unidirectional current-sense

amplifier, which offers precision accuracy specifications of

input offset voltage (VOS) of ±0.5μV (typ) and a gain error

of ±0.05% (typ).

Applying the VRS+ Supply and the Load

The EV kit is installed with a MAX49921FATA/VY+,

which has a 50V/V gain. The current-sense resistor R1

(RSENSE) value is 0.05Ω with ±0.5% tolerance. The

VOUT can be estimate by:

VOUT = ILOAD 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

0V to 70V.

Measuring the Load Current

The load current is measured as a voltage drop (VSENSE)

across an external sense resistor (R1). This voltage is

then amplified by the current-sense amplifier and pre-

sented at its VOUT pin. Like all differential amplifiers, the

output voltage has two components of error (an offset

error and a gain error). The offset error affects accuracy

at low currents and a gain error affects accuracy at large

currents. Both errors affect accuracy of measurement at

intermediate currents. By minimizing both offset and gain

errors, accuracy can be optimized over a wide dynamic

range.

Procedure

MAX49921 Evaluation

The MAX49921 EV kit is fully assembled and tested. Use

the following steps to verify board operation.

Caution: Do not turn on power supply or the elec-

tronic load until all connections are made.

1) Set the PS1 to 5V and turn it off. Connect the posi-

tive terminal of the PS1 to the VDD test point and the

negative terminal of the supply to the nearest GND

test point.

2) Set the PS2 to 12V (common-mode voltage) and

turn it off. Connect the positive terminal of the PS2 to

the VSENSE+ test point and the negative terminal of

the PS2 to the nearest GND test point.

3) Set the electronic load to sink 1A.

Note that the voltage at PS2 together with this 1A

load develops approximately 50mV input voltage

across the sense resistor (R1).

4) Connect the positive terminal of the electronic load

to the VSENSE- test point and the negative terminal

of the supply to the nearest GND test point.

5) Connect the first voltmeter between test points RS+

and RS- to measure VSENSE.

6) Connect the second voltmeter between VOUT and

the nearest GND test points.

7) Enable the PS1 and then PS2 power supplies.

8) Enable the electronic load.

Note that if the electronic load is not available,

remove the R1 sense resistor, and directly apply a

50mV sense voltage across the RS+ and RS- test

points.

9) Verify that the first voltmeter displays 50mV and the

second voltmeter displays 2.5V.

10) Disable the electronic load first, then turn off the PS2

and then PS1 last.

#Denotes RoHS compliance.

PART

U1 (INSTALLED)

TYPE

MAX49921EVKIT#

MAX49921FATA/VY+

EV Kit

Ordering Information

MAX49921 Datasheet(PDF) 2 Page - Maxim Integrated Products

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