DSPIC33FJMC202ESS datasheet(14/330 Pages) MICROCHIP

14 / 330 page

dsPIC33FJ32MC202/204 and dsPIC33FJ16MC304

DS70283K-page 14

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 con-

nects the power supply source to the device, and the

maximum current drawn by the device in the applica-

tion. 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, 16V connected to ground. The type

can be ceramic or tantalum. Refer to Section 24.0

“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 21.2

“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 capacitor C is 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

≤ 470W will limit any current flowing into

MCLR from the external capacitor C, in the

event of MCLR pin breakdown, due to Elec-

trostatic 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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