DSPIC33FJ32MC302 datasheet(18/460 Pages) MICROCHIP

18 / 460 page

dsPIC33FJ32MC302/304, dsPIC33FJ64MCX02/X04 AND dsPIC33FJ128MCX02/X04

DS70291G-page 18

FIGURE 2-1:

RECOMMENDED

MINIMUM CONNECTION

2.2.1

TANK CAPACITORS

On boards with power traces running longer than six

inches in length, it is suggested to use a tank capacitor

for integrated circuits including DSCs to supply a local

power source. The value of the tank capacitor should

be determined based on the trace resistance that

connects the power supply source to the device, and

the maximum current drawn by the device in the

application. In other words, select the tank capacitor so

that it meets the acceptable voltage sag at the device.

Typical values range from 4.7 µF to 47 µF.

2.3

CPU Logic Filter Capacitor

Connection (VCAP)

A low-ESR (< 5 Ohms) capacitor is required on the

VCAP pin, which is used to stabilize the voltage

regulator output voltage. The VCAP pin must not be

connected to VDD, and must have a capacitor between

4.7 µF and 10 µF, preferably surface mount connected

within one-eights inch of the VCAP pin connected to

ground. The type can be ceramic or tantalum. Refer to

Section 31.0

“Electrical

Characteristics”

for

additional information.

The placement of this capacitor should be close to the

VCAP. It is recommended that the trace length not

exceed one-quarter inch (6 mm). Refer to Section 28.2

“On-Chip Voltage Regulator” for details.

2.4

Master Clear (MCLR) Pin

The MCLR pin provides for two specific device

functions:

• Device Reset

• Device programming and debugging

During device programming and debugging, the

resistance and capacitance that can be added to the

pin must be considered. Device programmers and

debuggers drive the MCLR pin. Consequently,

specific voltage levels (VIH and VIL) and fast signal

transitions must not be adversely affected. Therefore,

specific values of R and C will need to be adjusted

based on the application and PCB requirements.

For example, as shown in Figure 2-2, it is

recommended that the capacitor C be isolated from the

MCLR pin during programming and debugging

operations.

Place the components shown in Figure 2-2 within

one-quarter inch (6 mm) from the MCLR pin.

FIGURE 2-2:

EXAMPLE OF MCLR PIN

CONNECTIONS

dsPIC33F

VDD

VSS

VDD

0.1 µF

Ceramic

0.1 µF

Ceramic

0.1 µF

Ceramic

0.1 µF

Ceramic

VDD

MCLR

0.1 µF

Ceramic

L1(1)

10 µF

Tantalum

Note 1:

As an option, instead of a hard-wired connection, an

inductor (L1) can be substituted between VDD and

AVDD to improve ADC noise rejection. The inductor

impedance should be less than 1

Ω and the inductor

capacity greater than 10 mA.

Where:

FCNV

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

π LC

()

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

πfC

()

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

⎝⎠

⎛⎞

(i.e., ADC conversion rate/2)

Note 1: R

≤ 10 kΩ is recommended. A suggested

starting value is 10 k

Ω. Ensure that the MCLR

pin VIH and VIL specifications are met.

2: R1

≤ 470Ω will limit any current flowing into

MCLR from the external capacitor C, in the

event of MCLR pin breakdown due to

Electrostatic Discharge (ESD) or Electrical

Overstress (EOS). Ensure that the MCLR pin

VIH and VIL specifications are met.

R1(2)

R(1)

VDD

MCLR

dsPIC33F

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