What does a weak pull-down resistor mean?

[Justinyuan]

what's meaning with the pull-down (weak) resistor?

The weak resistor means the value of the resistor is very small?

 

[barny451]

pull down resistor circuit

No, a weak pull-down is a large resistance (or equivalent, i.e. it might be an active device on a chip), as high a resistance as possible which overrides any leakage currents to guarantee a valid logic 0 voltage. Smaller values would waste power when driven high, higher values would not guarantee a logic 0.

 

[rajesh13]

weak pull down

Pull down resistor means how much resistance will be seen from the pin to gnd when a logic level 1 is connected to this pin.
Now come the question of strong pull up/down & weak pull up/down.

So as the name suggest that if it is strong pull up or pull down then the it is small resistor (or a large current source to strongly pull up)

& in case of weak pull up it equivalent resistance is very large say of the order of 100k. In present cmos circuits, these are realized using MOS(pull upa with pmos & pull down with nmos).

 

[mckinson]

weak pull down resistor

NOmarly , the value of the pull down resistor is 10 khom ?

 

[mhamed]

pulldown resistor

I think we use pulldown resistore for decreasing noise effecting on circuit which is exist after the pull down resistor.

but i have no idea about its order but think that 100k is large .isn't it?!!

 

[davyzhu]

pull-down resistor

Hello, the pull up or down resistor is to guarantee the current through the gate small, i.e. not large to destory the i/o gate. For eg, your power is 5v, resistor is 10k, so the current is below 5v/10k=0.5mA.

So when the power is 5v <->4.7k, 3.3v <->3.3k and so on...

Is that clear?

Regards,

Davy Zhu

 

[yjkwon57]

weak pulldown

Hi~~

In the complementary CMOS circuits, a PMOS or NMOS transistor is used as a pull-up or pull-down transistors, respectively. Any PMOS or NMOS transistor is to be always turned on by applying low-level or high-level voltage to its gate, repectively. Of course, you will not directly connect A Vdd or GND line to the gate due to the ESD problem. Instean, you will use a one- or zero-circuit cell for this purpose.

Bye~~

 

[rajesh13]

weak pull-down

Hi~~

In the complementary CMOS circuits, a PMOS or NMOS transistor is used as a pull-up or pull-down transistors, respectively. Any PMOS or NMOS transistor is to be always turned on by applying low-level or high-level voltage to its gate, repectively. Of course, you will not directly connect A Vdd or GND line to the gate due to the ESD problem. Instean, you will use a one- or zero-circuit cell for this purpose.

Bye~~

You can connect a Gate of nmos or pmos to either vdd or gnd. What matters is that if you are using proper ESD protection circuit. Like if you are using ggnMOS or an SCR then you can not connect directly (in such a case you have to use a series resistor). But if you are using a RC triggered ESD protection then in that case you can.