2001-2012 Microchip Technology Inc. DS21653C-page 9
MCP1525/41
4.0 APPLICATIONS INFORMATION
4.1 Application Tips
4.1.1 BASIC CIRCUIT CONFIGURATION
The MCP1525 and MCP1541 voltage reference
devices should be applied as shown in Figure 4-1 in all
applications.
FIGURE 4-1: Basic Circuit Configuration.
As shown in Figure 4-1, the input voltage is connected
to the device at the V
IN
input, with an optional 0.1 µF
ceramic capacitor. This capacitor would be required if
the input voltage has excess noise. A 0.1 µF capacitor
would reject input voltage noise at approximately
1 to 2 MHz. Noise below this frequency will be amply
rejected by the input voltage rejection of the voltage ref-
erence. Noise at frequencies above 2 MHz will be
beyond the bandwidth of the voltage reference and,
consequently, not transmitted from the input pin
through the device to the output.
The load capacitance (C
L
) is required in order to
stabilize the voltage reference; see Section 4.1.3
“Load Capacitor”.
4.1.2 INPUT (BYPASS) CAPACITOR
The MCP1525 and MCP1541 voltage references do
not require an input capacitor across V
IN
to V
SS
.
However, for added stability and input voltage transient
noise reduction, a 0.1 µF ceramic capacitor is
recommended, as shown in Figure 4-1. This capacitor
should be close to the device (within 5 mm of the pin).
4.1.3 LOAD CAPACITOR
The output capacitor from V
OUT
to V
SS
acts as a
frequency compensation for the references and cannot
be omitted. Use load capacitors between 1 µF and
10 µF to compensate these devices. A 10 µF output
capacitor has slightly better noise, and provides
additional charge for fast load transients, when
compared to a 1 µF output capacitor. This capacitor
should be close to the device (within 5 mm of the pin).
4.1.4 PRINTED CIRCUIT BOARD LAYOUT
CONSIDERATIONS
Mechanical stress due to Printed Circuit Board (PCB)
mounting can cause the output voltage to shift from its
initial value. Devices in the SOT-23-3 package are
generally more prone to assembly stress than devices
in the TO-92 package. To reduce stress-related output
voltage shifts, mount the reference on low-stress areas
of the PCB (i.e., away from PCB edges, screw holes
and large components).
4.1.5 OUTPUT FILTERING
If the noise at the output of these voltage references is
too high for the particular application, it can be easily
filtered with an external RC filter and op amp buffer.
The op amp’s input and output voltage ranges need to
include the reference output voltage.
FIGURE 4-2: Output Noise-Reducing
Filter.
The RC filter values are selected for a desired cutoff
frequency:
EQUATION 4-1:
The values that are shown in Figure 4-2 (10 k and
1 µF) will create a first-order, low-pass filter at the
output of the amplifier. The cutoff frequency of this filter
is 15.9 Hz, and the attenuation slope is 20 dB/decade.
The MCP6021 amplifier isolates the loading of this low-
pass filter from the remainder of the application circuit.
This amplifier also provides additional drive, with a
faster response time than the voltage reference.
V
SS
V
OUT
V
IN
V
REF
V
DD
MCP1525
MCP1541
C
L
1 µF to 10 µF
C
IN
0.1 µF
(optional)
V
SS
V
OUT
V
IN
C
L
R
FIL
MCP1525
MCP1541
10 µF
10 kW
C
FIL
1µF
V
DD
V
REF
MCP6021
V
DD
f
C
1
2R
FIL
C
FIL
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21653C.book Page 9 Thursday, January 10, 2013 12:55 PM
