MAX9944(2009) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX9944
(Rev.:2009)

High-Voltage, Precision, Low-Power Op Amps

Maxim Integrated 

High-Voltage, Precision, Low-Power Op Amps

Power Supplies and Layout

The MAX9943/MAX9944 can operate with dual supplies

from ±3V to ±19V or with a single supply from +6V to

+38V with respect to ground. When used with dual sup-

plies, bypass both VCC and VEE with their own 0.1µF

capacitor to ground. When used with a single supply,

bypass VCC with a 0.1µF capacitor to ground. Careful

layout technique helps optimize performance by

decreasing the amount of stray capacitance at the op

amp’s inputs and outputs. To decrease stray capaci-

tance, minimize trace lengths by placing external com-

ponents close to the op amp’s pins.

Output Current Capability

The MAX9943/MAX9944 are capable of driving heavy

loads such as the ones that can be found in loop-pow-

ered systems for remote sensors. The information is

transmitted through ±20mA or 4mA–20mA current output

across long lines that are terminated with low resistance

loads (e.g., 600Ω). The Typical Application Circuit shows

the MAX9944 used as a voltage-to-current converter with

a current-sense amplifier in the feedback loop. Because

of the high output current capability of the MAX9944, the

device can be used to directly drive the current-loop.

The specifications and operation of the MAX9943/

MAX9944 family is guaranteed over the -40°C to

+125°C temperature range, However, when used in

applications with ±15V supply voltage (see Figure 3),

the capability of driving more than ±20mA of current is

limited to the -40°C to +85°C temperature range. Use a

lower supply voltage if this current must be delivered at

a higher temperature range.

Input Common Mode and Output Swing

The MAX9943/MAX9944 input common-mode range

can swing to the negative rail VEE. The output voltage

can swing to both the positive VCC and the negative

VEE rails if the output stage is not heavily loaded. These

two features are very important for applications where

the MAX9943/ MAX9944 are used with a single-supply

(VEE connected to ground). One of the applications that

can benefit from these features is when the single-sup-

ply op amp is driving an ADC.

INPUT

MAX9943

RISO

OUTPUT

CL

Figure 1. Capacitive Load Driving Circuit

1.5kΩ

1.5kΩ

Figure 2. Input Protection Circuit

Input Differential Voltage Protection

During normal op-amp operation, the inverting and non-

inverting inputs of the MAX9943/MAX9944 are at essen-

tially the same voltage. However, either due to fast

input voltage transients or due to other fault conditions,

these pins can be forced to be at two different voltages.

Internal back-to-back diodes and series resistors pro-

tect the inputs from an excessive differential voltage

(see Figure 2). Therefore, IN+ and IN- can be any volt-

age within the range shown in the absolute maximum

rating. Note the protection time is still dependent on the

package thermal limits.

Chip Information

PROCESS: BiCMOS

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