Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

MCLR connection on PIC24FJ1024GB610?

Status
Not open for further replies.

cupoftea

Advanced Member level 6
Advanced Member level 6
Joined
Jun 13, 2021
Messages
3,057
Helped
62
Reputation
124
Reaction score
139
Trophy points
63
Activity points
15,948
Hi,

With the MCLR pin on a PIC24FJ1024GB610 supplied by 3V3, would you ever consider connecting the MCLR with just a 2k2 in parallel with 100nF to the 3V3? Wouldn’t the 100nF be too big and deform the programming pulses?



Also, isn’t it more usual to have a 10n from MCLR to GND, and then a 10k from MCLR to 3V3?
 

Solution
The MCLR input for most Microchip controllers has a dual purpose.

First is to provide an R-C delay after power on before the controller starts to execute code.

Second is initialize the state machine to detect In-Circuit-Serial-Programming(ICSP) start mode.

For this second purpose it is helpful to have a resistor to isolate the capacitor to ground from the MCLR input.

Note that the ICSP tool is connect to the MCLR pin of the controller and the R2 resistor isolates the influence of the C1 capacitor from the VPP/MCLR signal of the ICSP tool.

Recommended values: R1 = 10K ohm, R2 = 470 ohm, C1 = 100nF.

This Image found in data sheet DS30010074D-page 41:

1625595209077.png
The MCLR input for most Microchip controllers has a dual purpose.

First is to provide an R-C delay after power on before the controller starts to execute code.

Second is initialize the state machine to detect In-Circuit-Serial-Programming(ICSP) start mode.

For this second purpose it is helpful to have a resistor to isolate the capacitor to ground from the MCLR input.

Note that the ICSP tool is connect to the MCLR pin of the controller and the R2 resistor isolates the influence of the C1 capacitor from the VPP/MCLR signal of the ICSP tool.

Recommended values: R1 = 10K ohm, R2 = 470 ohm, C1 = 100nF.

This Image found in data sheet DS30010074D-page 41:

1625595209077.png
 
Solution
Althought the RC constant on this particular case is fairly small in the range of 1ms, as a general rule of thumb, regardless of its time constant, I also add an anti-parallel diode near to R1, just to ensure that a quick under-voltage disturbance on VDD would also generate negative trigger the MCLR\ pin.
 

    cupoftea

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top