MCP604-E/SN Microchip Technology, MCP604-E/SN Datasheet - Page 12

• Manufacturer Part Number: MCP604-E/SN
• Description: 2.7V to 5.5V Single Supply CMOS Op Amps
• Manufacturer: Microchip Technology

MCP601/2/3/4
FIGURE 3-3:
for capacitive loads.
Once you’ve selected R
check the resulting frequency response peaking and
step response overshoot in your circuit. Evaluation on
the bench and simulations with the MCP601/2/3/4
SPICE macro model are very helpful. Modify R
value until the response is reasonable.
3.5
With this family of op amps, the power supply pin (V
for single-supply) should have a local bypass capacitor
(i.e., 0.01 µF to 0.1 µF) within 2 mm for good high-fre-
quency performance. It also needs 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 parts.
3.6
In applications where low input bias current is critical,
printed circuit board (PCB) surface leakage effects
need to be considered. Surface leakage is caused by
humidity, dust or other contamination on the board.
Under low humidity conditions, a typical resistance
between nearby traces is 10
would cause 5 pA of current to flow. This is greater
than the MCP601/2/3/4 family’s bias current at +25°C
(1 pA, typ.).
The easiest way to reduce surface leakage is to use a
guard ring around sensitive pins (or traces). The guard
ring is biased at the same voltage as the sensitive pin.
An example of this type of layout is shown in
Figure 3-4.
FIGURE 3-4:
DS21314F-page 12
100
1k
10
10p
1,000
100
10
Supply Bypass
PCB Surface Leakage
10
Guard Ring
Normalized Load Capacitance; C
100p
100
Recommended R
Example Guard Ring layout.
G
G
N
N
ISO
= +1
V
+2
IN–
for your circuit, double-
12
V
IN+
1n
. A 5V difference
1,000
L
/ G
ISO
N
(F)
values
10n
10,000
ISO
DD
’s
1.
2.
3.7
3.7.1
Figure 3-5 and Figure 3-6 show low-pass, second-
order, Butterworth filters with a cutoff frequency of
10 Hz. The filter in Figure 3-5 has a non-inverting gain
of +1 V/V, and the filter in Figure 3-6 has an inverting
gain of -1 V/V.
FIGURE 3-5:
Sallen-Key Filter.
FIGURE 3-6:
Multiple-Feedback Filter.
The MCP601/2/3/4 family of op amps have low input
bias current, which allows the designer to select larger
resistor values and smaller capacitor values for these
filters. This helps produce a compact PCB layout.
These filters, and others, can be designed using
Microchip’s FilterLab
V
V
IN
IN
Connect the guard ring to the inverting input pin
(V
ing unity-gain buffers. This biases the guard ring
to the common mode input voltage.
Connect the guard ring to the non-inverting input
pin (V
transimpedance amplifiers (converts current to
voltage, such as photo detectors). This biases
the guard ring to the same reference voltage as
the op amp (e.g., V
IN
618 k
382 k
47 nF
–) for non-inverting gain amplifiers, includ-
Typical Applications
R
C
R
2
1
IN
1
ANALOG FILTERS
+) for inverting gain amplifiers and
1.00 M
618 k
47 nF
641 k
V
22 nF
C
R
R
DD
R
C
1
3
2
2
®
2
/2
software.
Second-Order, Low-Pass
Second-Order, Low-Pass
DD
2004 Microchip Technology Inc.
/2 or ground).
MCP60X
+
–
+
–
MCP60X
8.2 nF
C
1
G = +1 V/V
f
P
G = -1 V/V
f
P
= 10 Hz
= 10 Hz
V
V
OUT
OUT