MCP6232-E/SNG Microchip Technology, MCP6232-E/SNG Datasheet - Page 11

• Manufacturer Part Number: MCP6232-E/SNG
• Description: 1.8V, 200KHz DUAL LOW-COST CMOS OPERATIONAL AMPLIFIER, -40C to +125C, 8-SOIC 150mil, TUBE
• Manufacturer: Microchip Technology

A significant amount of current can flow out of the
inputs when the common mode voltage (V
ground (V
high impedance may need to limit the useable voltage
range.
4.1.3
The input stage of the MCP6231/1R/1U/2/4 op amps
use two differential CMOS input stages in parallel. One
operates at low common mode input voltage (V
while the other operates at high V
ogy, the device operates with V
V
4.2
The output voltage range of the MCP6231/1R/1U/2/4
op amps is V
(minimum) when R
V
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 4-4:
stabilizes large capacitive loads.
Figure 4-5
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
© 2008 Microchip Technology Inc.
DD
DD
V
IN
and 0.3V below V
= 5.5V. Refer to
Rail-to-Rail Output
Capacitive Loads
SS
NORMAL OPERATION
gives recommended R
); see
DD
–
+
MCP623X
– 35 mV (maximum) and V
ISO
L
Figure
= 10 kΩ is connected to V
Figure 2-14
in
SS
Output resistor, R
Figure
.
2-19. Applications that are
R
4-4) improves the feed-
L
ISO
CM
/G
for more information.
CM
C
N
up to 0.3V above
), where G
L
. WIth this topol-
ISO
N
= +2 V/V).
CM
ISO
SS
values for
) is below
N
DD
+ 35 mV
V
and the
N
OUT
/2 and
is the
N
CM
is
),
FIGURE 4-5:
for Capacitive Loads.
After selecting R
resulting frequency response peaking and step
response overshoot. Evaluation on the bench and
simulations with the MCP6231/1R/1U/2/4 SPICE
macro model are very helpful. Modify R
the response is reasonable.
4.4
With this op amp, the power supply pin (V
single-supply) should have a local bypass capacitor
(i.e., 0.01 µF to 0.1 µF) within 2 mm for good high-
frequency performance. It can use a bulk capacitor
(i.e., 1 µF or larger) within 100 mm to provide large,
slow currents. This bulk capacitor can be shared with
other nearby analog parts.
4.5
An unused op amp in a quad package (MCP6234)
should be configured as shown in
circuits prevent the output from toggling and causing
crosstalk. Circuit A can use any reference voltage
between the supplies, provides a buffered DC voltage
and minimizes the supply current draw of the unused
op amp. Circuit B minimizes the number of
components, but may draw a little more supply current
for the unused op amp.
FIGURE 4-6:
V
MCP6231/1R/1U/2/4
DD
10,000
¼ MCP6234 (A)
1,000
R
R
V
100
10k
100
REF
1k
1
2
10p
Supply Bypass
Unused Op Amps
10
=
Normalized Load Capacitance; C
V
V
DD
DD
ISO
⋅
------------------
R
for your circuit, double-check the
100p
1
100
R
Recommended R
Unused Op Amps.
+
2
V
R
2
REF
G
G
G
N
N
N
= 1 V/V
= 2 V/V
≥ 4 V/V
1000
1n
¼ MCP6234 (B)
DS21881D-page 11
Figure
ISO
L
/G
’s value until
ISO
V
N
DD
(F)
4-6. Both
Values
10000
10n
DD
for