MAX9643 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX9643

60V High-Speed Precision Current-Sense Amplifier

Maxim Integrated 

MAX9643

60V High-Speed Precision Current-Sense Amplifier

input voltage transients below -3.5V should be limited by

the use of input series resistors. For example, if an input

voltage transient or fault condition of -12V were to occur

in the application, use a resistor greater than 8.5V/5mA =

1700Ω. Use 2kΩ for margin.

The maximum input common-mode voltage extends up to

60V over the entire VCC range of 2.7V to 36V. It is recom-

mended to shield the device from overvoltages above its

65V absolute maximum rating to protect the device.

Output Voltage Range

The internal negative voltage rail generated by the charge

pump is also used to bias the output stage of the current-

sense amplifier, allowing it to feature true VOL = 0V per-

formance. This feature allows small sense voltages to be

used and eases interface to other analog and mixed-signal

ICs. In reality, attaining true VOL = 0V specification is usu-

ally limited by the offset voltage of the current-sense ampli-

fier since VOUT = VOS x gain, when input VSENSE = 0V.

In addition, the maximum output voltage of the IC is inter-

nally clamped to less than 5V even when it is powered

from a 40V rail. This allows easy interface to low-voltage

downstream circuitry without worrying about protecting

them from large input voltage transients or faults.

Common Mode and Differential Filtering

When the AC common-mode signal with large amplitudes

(>5VP-P for example) at high frequencies (> 1kHz for

example) is present at the inputs, AC CMRR limitation

causes spikes at the output as shown in the Common

Mode graph in the Typical Operating Characteristics.

Application Note 3888: Performance of Current-Sense

Amplifiers with Input Series Resistors explains the way to

filter out these common-mode transients as seen by the

amplifier and filtering of the differential mode.

Choosing the Sense Resistor

Choose RSENSE based on the following criteria:

• Voltage loss: A high RSENSE value causes the

power-source voltage to reduce due to IR drop. For

minimal voltage loss, use the lowest RSENSE value.

• Accuracy: A high RSENSE value allows lower cur-

rents to be measured more accurately. This is because

input offset voltages become less significant when the

sense voltage is larger.

• Efficiency and power dissipation: At high current

levels, the I2R losses in RSENSE can be 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 allowed to

heat up excessively.

• Inductance: Keep inductance low if ISENSE has a

large high-frequency component. Because of the high

currents that flow through RSENSE, take care to elimi-

nate 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.

Power-Supply Bypassing and Grounding

For most applications, bypass VCC to GND with a 0.1µF

ceramic capacitor. In many applications, VCC can be

connected to one of the current monitor terminals (RS+

or RS-). Because VCC is independent of the monitored

voltage, VCC can be connected to a separate regulated

supply. There are no specific power-supply sequencing

issues to consider. The part can withstand 60V input

common-mode voltages even when VCC = 0V, and main-

tains a high input impedance in this application condition.

Chip Information

PROCESS: BiCMOS

Ordering Information

PART

PIN-

PACKAGE

GAIN

(V/V)

TEMP

RANGE

MAX9643TATA+ 8 TDFN-EP* 2.5 -40°C to +125°C

MAX9643UATA+ 8 TDFN-EP* 10 -40°C to +125°C

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed paddle.

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