MCP6234 Microchip Technology, MCP6234 Datasheet - Page 8

• Manufacturer Part Number: MCP6234
• Description: 300 kHz Rail-to-Rail Op Amp
• Manufacturer: Microchip Technology

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MCP6231/2/4
4.0
The MCP6231/2/4 family of op amps is manufactured
using Microchip’s state-of-the-art CMOS process and
is specifically designed for low-cost, low-power and
general-purpose applications. The low supply voltage,
low quiescent current and wide bandwidth makes the
MCP6231/2/4 ideal for battery-powered applications.
4.1
The MCP6231/2/4 op amps are designed to prevent
phase reversal when the input pins exceed the supply
voltages. Figure 4-1 shows the input voltage exceeding
the supply voltage without any phase reversal.
FIGURE 4-1:
Phase Reversal.
The input stage of the MCP6231/2/4 op amps use two
differential input stages in parallel. One operates at low
common mode input voltage (V
high V
V
The
V
proper operation.
Input voltages that exceed the input voltage range
(V
excessive current to flow into or out of the input pins.
Current beyond ±2 mA can cause reliability problems.
Applications that exceed this rating must be externally
limited with a resistor, as shown in Figure 4-2.
DS21881C-page 8
CM
CM
SS
up to 300 mV above V
= V
– 0.3V to V
-1.0
CM
6.0
5.0
4.0
3.0
2.0
1.0
0.0
input
SS
APPLICATION INFORMATION
Rail-to-Rail Inputs
. With this topology, the device operates with
– 300 mV and V
offset
DD
+ 0.3V at 25°C) can cause
The
voltage
V
Time (1 ms/div)
IN
DD
MCP6231/2/4
DD
V
and 300 mV below V
OUT
CM
+ 300 mV to ensure
is
) and the other at
measured
V
G = +2 V/V
Show No
DD
= 5.0V
SS
at
.
FIGURE 4-2:
Resistor (R
4.2
The output voltage range of the MCP6231/2/4 op amps
is V
R
Refer to Figure 2-14 for more information.
4.3
Driving large capacitive loads can cause stability
problems for voltage feedback op amps. As the load
capacitance increases, the feedback loop’s phase
margin decreases and the closed-loop bandwidth is
reduced. This produces gain peaking in the frequency
response, with overshoot and ringing in the step
response. A unity-gain buffer (G = +1) is the most
sensitive to capacitive loads, but all gains show the
same general behavior.
When driving large capacitive loads with these op
amps (e.g., > 60 pF when G = +1), a small series resis-
tor at the output (R
back loop’s phase margin (stability) by making the
output load resistive at higher frequencies. The band-
width will be generally lower than the bandwidth with no
capacitive load.
FIGURE 4-3:
stabilizes large capacitive loads.
Figure 4-4 gives recommended R
different capacitive loads and gains. The x-axis is the
normalized load capacitance (C
circuit’s noise gain. For non-inverting gains, G
signal gain are equal. For inverting gains, G
1 + |Signal Gain| (e.g., –1 V/V gives G
L
V
= 10 k
DD
IN
V
IN
– 35 mV (max.) and V
Rail-to-Rail Output
Capacitive Loads
R
R
IN
IN
is connected to V
IN
–
MCP623X
+
).
------------------------------------------------------------------------------ -
R
V
--------------------------------------------------------------------------- -
Maximum expected V
IN
SS
ISO
–
in Figure 4-3) improves the feed-
Minimum expected V
Input Current-Limiting
Output resistor, R
© 2005 Microchip Technology Inc.
–
+
MCP623X
2 mA
2 mA
SS
R
DD
L
ISO
/G
+ 35 mV (min.) when
/2 and V
C
N
IN
), where G
L
ISO
N
–
= +2 V/V).
V
IN
DD
ISO
DD
values for
N
V
V
= 5.5V.
OUT
N
and the
OUT
is the
N
is