MAX9934TAUA 데이터 시트보기 (PDF) - Maxim Integrated

부품명

상세내역

제조사

MAX9934TAUA

High-Precision, Low-Voltage, Current-Sense Amplifier with Current Output and Chip Select for Multiplexing

Maxim Integrated 

High-Precision, Low-Voltage, Current-Sense Amplifier

with Current Output and Chip Select for Multiplexing

1.8V

VCS

0V

VOUT

% FINAL VALUE

tHZ

tZH

Figure 2. Output Select and Deselect Time

100mV

3.3V

VCC

0V

VOUT

2.5V

% FINAL VALUE

tPD

tPU

100mV

Figure 3. Output Power-Up and Power-Down Time

voltage. Further, when VCC = 0, the amplifier maintains

an extremely high impedance on both its inputs and

output, up to the maximum operating voltages (see the

Absolute Maximum Ratings section).

The MAX9934 features a CS that can be used to dese-

lect its output current-source. This allows multiple cur-

rent-sense amplifier outputs to be multiplexed into a

single ADC channel with a single ROUT. See the Chip

Select Functionality for Multiplexed Systems section for

more details.

The Functional Diagram shows the internal operation of

the MAX9934. At its core is the indirect current-feed-

back architecture. This architecture uses two matched

transconductance amplifiers to convert their input dif-

ferential voltages into an output current. A high-gain

feedback amplifier forces the voltage drop across

RGAIN to be the same as the input differential voltage.

The internal resistor (RGAIN) sets the transconductance

gain of the device. Both input and output transconduc-

tance amplifiers feature excellent common-mode rejec-

tion characteristics, helping the MAX9934 to deliver

industry-leading precision specifications over the full

common-mode range.

Applications Information

Advantages of Current-Output

Architecture

The transconductance transfer function of the MAX9934

converts input differential voltage to an output current.

An output termination resistor, ROUT, then converts this

current to a voltage. In a large circuit board with multi-

ple ground planes and multiple current-measurement

rails spread across the board, traditional voltage-output

current-sense amplifiers become susceptible to

ground-bounce errors. These errors occur because the

local ground at the location of the current-sense amplifi-

er is at a slightly different voltage than the local ground

voltage at the ADC that is sampling the voltage. The

MAX9934 allows accurate measurements to be made

even in the presence of system ground noise. This is

achieved by sending the output information as a cur-

rent, and by terminating to the ADC ground.

A further advantage of current-output systems is the

flexibility in setting final voltage gain of the device.

Since the final voltage gain is user-controlled by the

choice of output termination resistor, it is easy to opti-

mize the monitored load current range to the ADC input

voltage range. It is no longer necessary to increase the

size of the sense resistor (also increasing power dissi-

pation) as necessary with fixed-gain, voltage-output

current-sense amplifiers.

______________________________________________________________________________________ 11

Share Link: