Pull-up resistors

Thread Starter

satcom

Joined Apr 1, 2015
65
I need ISP program of Winbond W25Q32BV chip (without removing it from board): as noted in Manual, the WP and HOLD pins must be pulled up to high with resistor: so its need be connected to VCC pin of the flash via the he pull-up resistor. Should it be one resistor between the Pin2 of ISP port connected via 2 lines: one line directly to VCC pin of the flash, and 2nd line to WP and HOLD pins of chip through the pull-up resistor? Or 2 resistors, one in each line,i.e. one between WP and VCC pin of chip and another between HOLD and VCC pin of chip? What is denomination of this pull-up resistor(s)?

connection.png
 

dendad

Joined Feb 20, 2016
3,602
I would think 2 resistors. That way you have the capability of driving each pin independently if you need to.
Without looking at the chip data, you could try a couple of 47K resistors.
 

Thread Starter

satcom

Joined Apr 1, 2015
65
I would think 2 resistors. That way you have the capability of driving each pin independently if you need to.
Without looking at the chip data, you could try a couple of 47K resistors.
What if 10K resistor nominal, would it be enough?
 

dendad

Joined Feb 20, 2016
3,602
Try it and see.
A lot depends on the application. 10K may be better than 47K, and you may even need to go lower if the pins are switching fast.
 

Irving

Joined Jan 30, 2016
1,014
Yes, but that depends on it being in a low noise environment. Lower values will give better noise immunity.
Then might as well connect to Vcc as per OP's original schematic as these are only used to stall programming operation if source data not ready. They perform no function unless programming, though it is recommended to tie WP low on operational board to make EEPROM effectively a ROM.
 
Top