MCP1525ISLASHTT datasheet(9/20 Pages) MICROCHIP

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 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 VIN 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

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 VIN to VSS.

However, for added stability and input voltage transient

noise

reduction,

0.1 µF

ceramic

capacitor

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 VOUT to VSS 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.

VSS

VOUT

VIN

VREF

VDD

MCP1525

MCP1541

1 µF to 10 µF

CIN

0.1 µF

(optional)

VSS

VOUT

VIN

RFIL

MCP1525

MCP1541

10 µF

10 kW

CFIL

1µF

VDD

VREF

MCP6021

VDD

R

FILCFIL

------------------------------

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