DSPIC33FJ32MC302 datasheet(19/460 Pages) MICROCHIP

19 / 460 page

DS70291G-page 19

dsPIC33FJ32MC302/304, dsPIC33FJ64MCX02/X04 AND dsPIC33FJ128MCX02/X04

2.5

ICSP Pins

The PGECx and PGEDx pins are used for In-Circuit

Serial Programming™ (ICSP™) and debugging

purposes. It is recommended to keep the trace length

between the ICSP connector and the ICSP pins on the

device as short as possible. If the ICSP connector is

expected to experience an ESD event, a series resistor

is recommended with a value in the range of a few tens

of Ohms, not to exceed 100 Ohms.

Pull-up resistors, series diodes, and capacitors on the

PGECx and PGEDx pins are not recommended as they

will

interfere

with

the

programmer/debugger

communications to the device. If such discrete

components are an application requirement, they

should

removed

from

the

circuit

during

programming and debugging. Alternatively, refer to the

AC/DC characteristics and timing requirements

information

the

respective

device

Flash

programming

specification

for

information

capacitive loading limits and pin input voltage high (VIH)

and input low (VIL) requirements.

Ensure that the “Communication Channel Select” (i.e.,

PGECx/PGEDx pins) programmed into the device

matches the physical connections for the ICSP to

MPLAB® ICD 3 or MPLAB REAL ICE™.

For more information on ICD 3 and REAL ICE

connection requirements, refer to the following

documents that are available on the Microchip web

site.

• “Using MPLAB® ICD 3” (poster) (DS51765)

• “MPLAB® ICD 3 Design Advisory” (DS51764)

• “MPLAB® REAL ICE™ In-Circuit Emulator User’s

Guide” (DS51616)

• “Using MPLAB® REAL ICE™” (poster) (DS51749)

2.6

External Oscillator Pins

Many DSCs have options for at least two oscillators: a

high-frequency primary oscillator and a low-frequency

secondary oscillator (refer to Section 9.0 “Oscillator

Configuration” for details).

The oscillator circuit should be placed on the same

side of the board as the device. Also, place the

oscillator circuit close to the respective oscillator pins,

not exceeding one-half inch (12 mm) distance

between them. The load capacitors should be placed

next to the oscillator itself, on the same side of the

board. Use a grounded copper pour around the

oscillator circuit to isolate them from surrounding

circuits. The grounded copper pour should be routed

directly to the MCU ground. Do not run any signal

traces or power traces inside the ground pour. Also, if

using a two-sided board, avoid any traces on the

other side of the board where the crystal is placed. A

suggested

layout

shown

Figure 2-3.

Recommendations

for

crystals

and

ceramic

resonators are provided in Table 2-1 and Table 2-2,

respectively.

FIGURE 2-3:

SUGGESTED PLACEMENT

OF THE OSCILLATOR

CIRCUIT

TABLE 2-1:

CRYSTAL RECOMMENDATIONS

Main Oscillator

Guard Ring

Guard Trace

Secondary

Oscillator

Part

Number

Vendor

Freq.

Load

Cap.

Package

Case

Frequency

Tolerance

Mounting

Type

Operating

Temperature

ECS-40-20-4DN

ECS Inc.

4 MHz

20 pF

HC49/US

±30 ppm

-40°C to +85°C

ECS-80-18-4DN

ECS Inc.

8 MHz

18 pF

HC49/US

±30 ppm

-40°C to +85°C

ECS-100-18-4-DN

ECS Inc.

10 MHz

18 pF

HC49/US

±30 ppm

-40°C to +85°C

ECS-200-20-4DN

ECS Inc.

20 MHz

20 pF

HC49/US

±30 ppm

-40°C to +85°C

ECS-40-20-5G3XDS-TR

ECS Inc.

4 MHz

20 pF

HC49/US

±30 ppm

-40°C to +125°C

ECS-80-20-5G3XDS-TR

ECS Inc.

8 MHz

20 pF

HC49/US

±30 ppm

-40°C to +125°C

ECS-100-20-5G3XDS-TR ECS Inc.

10 MHz

20 pF

HC49/US

±30 ppm

-40°C to +125°C

ECS-200-20-5G3XDS-TR ECS Inc.

20 MHz

20 pF

HC49/US

±30 ppm

-40°C to 125°C

NX3225SA 20MHZ AT-W NDK

20 MHz

8 pF

3.2 mm x 2.5 mm

±50 ppm

-40°C to 125°C

Legend:

TH = Through Hole

SM = Surface Mount

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