MAX44281(2012) 데이터 시트보기 (PDF) - Maxim Integrated
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MAX44281 Datasheet PDF : 10 Pages
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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 combination 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 equipment.
Shutdown Mode
The MAX44281 features shutdown functionality by pulling
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
protection 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-channel 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
sampling rate, but just 6FA at 1ksps and 0.5FA in shut
down. 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
Maxim Integrated
8
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