MCP654 MICROCHIP [Microchip Technology], MCP654 Datasheet - Page 28

• Manufacturer Part Number: MCP654
• Description: 50 MHz, 6 mA Op Amps with mCal
• Manufacturer: MICROCHIP [Microchip Technology]

MCP651/2/4/5/9
FIGURE 4-11:
Capacitance.
C
which causes an increase in gain at high frequencies.
C
loop, which becomes less stable. This effect can be
reduced by either reducing C
C
at V
The largest value of R
on noise gain (see G
Loads”) and C
recommended R
FIGURE 4-12:
R
Figure 2-37
large signal step responses at G = +1 V/V. The unity
gain buffer usually has R
Figure 2-39
large signal step responses at G = -1 V/V. Since the
noise gain is 2 V/V and C
chosen to be R
It is also possible to add a capacitor (C
R
This makes it possible to use larger values of R
conditions
Equation
DS22146B-page 28
G
G
N
F
F
acts in parallel with R
and R
vs. Gain.
to compensate for the de-stabilizing effect of C
P
also reduces the phase margin of the feedback
. This filter has a single real pole at 1/(2πR
1.E+05
1.E+04
1.E+03
1.E+02
100k
10k
100
V
1k
4-10.
V
N
M
P
form a low-pass filter that affects the signal
1
and
and
C
C
for
C
C
G
G
C
G
G
= 100 pF
= 320 pF
F
G
= 10 pF
= 32 pF
G
Figure 2-38
Figure 2-40
R
R
F
= 1 nF
= R
.
N
G
for several C
stability
Figure 4-12
G
N
Amplifier with Parasitic
Maximum Recommended
= 499Ω and R
F
Noise Gain; G
C
C
G
in Section 4.4.1 “Capacitive
that should be used depends
F
N
G
G
G
(except for a gain of +1 V/V),
= 0Ω and R
N
≈ 10 pF, the resistors were
R
> +1 V/V
MCP65X
show the small signal and
show the small signal and
G
F
10
are
or R
G
shows the maximum
values.
N
F
(V/V)
.
N
summarized
F
G
= 249Ω.
) in parallel with
V
open.
OUT
N
F
C
100
. The
N
).
G
in
.
EQUATION 4-10:
4.5
With this family of operational amplifiers, the power
supply pin (V
bypass capacitor (i.e., 0.01 µF to 0.1 µF) within 2 mm
for good high frequency performance. Surface mount,
multilayer ceramic capacitors, or their equivalent,
should be used.
These op amps require a bulk capacitor (i.e., 2.2 µF or
larger) within 50 mm to provide large, slow currents.
Tantalum capacitors, or their equivalent, may be a good
choice. This bulk capacitor can be shared with other
nearby analog parts as long as crosstalk through the
supplies does not prove to be a problem.
4.6
These op amps are fast enough that a little extra care
in the PCB (Printed Circuit Board) layout can make a
significant difference in performance. Good PC board
layout
performance shown in the specifications and Typical
Performance Curves; it will also help you minimize
EMC (Electro-Magnetic Compatibility) issues.
Use a solid ground plane. Connect the bypass local
capacitor(s) to this plane with minimal length traces.
This cuts down inductive and capacitive crosstalk.
Separate digital from analog, low speed from high
speed, and low power from high power. This will reduce
interference.
Keep sensitive traces short and straight. Separate
them from interfering components and traces. This is
especially important for high frequency (low rise time)
signals.
Sometimes, it helps to place guard traces next to victim
traces. They should be on both sides of the victim
trace, and as close as possible. Connect guard traces
to ground plane at both ends, and in the middle for long
traces.
Use coax cables, or low inductance wiring, to route
signal and power to and from the PCB. Mutual and self
inductance of power wires is often a cause of crosstalk
and unusual behavior.
Given:
We need:
G
G
f
f
f
f
F
Z
F
F
N1
N2
≤
≤
=
=
techniques
Power Supply
High Speed PCB Layout
f
f
GBWP
GBWP
=
=
f
1
F
(
⁄
1
1
DD
G
(
2
+
+
N1
π
⁄
⁄
for single supply) should have a local
R
C
(
(
R
⁄
2G
4G
F
G
F
G
C
⁄
⁄
N2
R
N2
N1
C
F
will
G
)
F
)
)
)
© 2011 Microchip Technology Inc.
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, G
help
N1
N1
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G
G
you
N2
N2
achieve
the