MAX44281U Просмотр технического описания (PDF) - Maxim Integrated

Номер в каталоге

Компоненты Описание

производитель

MAX44281U

Ultra-Small, Ultra-Thin, 4-Bump Op Amp

Maxim Integrated 

MAX44281

Ultra-Small, Ultra-Thin, 4-Bump Op Amp

Detailed Description

Rail-to-Rail Output Stage

The MAX44281 is a high-bandwidth, low-power op amp in

the smallest 4-bump WLP industry package. Its combina-

tion of precision, low-noise, and low-power specifications

makes it ideal for use in a wide variety of sensor interface

applications in portable consumer and medical equip-

ment.

Shutdown Mode

The MAX44281 features shutdown functionality by pull-

ing VDD to ground. During shutdown, both the input and

the output are high-impedance. The input and output of

the MAX44281 enter a high-impedance state when the

device enters shutdown. Since shutdown is triggered by

lowering the supply voltage to below 0.5V, the ESD pro-

tection diodes at the output limit the high-Z voltage range

of the output. Diode D2 in Figure 2, from the output of

the amplifier to VDD, is forward biased when the output

voltage becomes too high in shutdown mode. The diodes

combined with the low-voltage shutdown functionality

effectively limit the high-impedance output range to plus

and minus a diode voltage around ground (~P 0.6V).

Driving Capacitive Loads

Driving a capacitive load can cause instability in many op

amps, especially those with low quiescent current. The

MAX44281 is stable for a range of capacitive loads to

above 400pF. Adding a series resistor between the output

and the load capacitor improves the circuit’s response by

isolating the load capacitance from the op amp’s output.

See the Isolation Resistance vs. Capacitive-Load Stability

graph in the Typical Operating Characteristics section for

details.

Applications Information

The MAX44281 features low input voltage offset and low

bias current, which makes the device ideal for single-

supply DC operations. However, its wide bandwidth and

low noise make it suitable also for AC applications. The

circuit in Figure 1 enables AC-coupled applications with

the simple addition of two external resistors R1 and R2.

Such resistors set the output bias voltage at midsupply.

The values of R1 and R2 depend on the gain option of the

device, according to the equation:

●● VDD x (R2/(R1 + R2)) = VDD/(2 x AV)

Driver for Interfacing with

the MAX11645 ADC

The MAX44281’s tiny size and low noise make it a good

fit for driving 12- to 16-bit resolution ADCs in space-

constrained applications. The Typical Application Circuit

shows the MAX44281 amplifier output connected to a

lowpass filter driving the MAX11645 ADC. The MAX11645

is part of a family of 3V and 5V, 12-bit and 10-bit, 2-chan-

nel ADCs.

The MAX11645 offers sample rates up to 94ksps and

measures two single-ended inputs or one differential

input. These ADCs dissipate 670FA at the maximum sam-

pling rate, but just 6µA at 1ksps and 0.5µA in shutd­ own.

Offered in the ultra-tiny, 1.9mm x 2.2mm WLP and FMAX-

8 packages, the MAX11645 ADCs are an ideal fit to pair

with the MAX44281 amplifier in por­table applications.

Where higher resolution is required, refer to the MAX1069

(14-bit) and MAX1169 (16-bit) ADC families.

VDD

R1

C

IN

VIN

R2

VDD

MAX44281

OUT

VOUT

GND

Figure 1. How to Use the MAX44281 in AC-Coupled

Applications

VDD

D2

OUT

D1

GND

Figure 2. Output ESD Protection Diodes

www.maximintegrated.com

Maxim Integrated │  8

Share Link: