Difference between PMOS LDO and NMOS LDO

Hari T O0

Genius 3820 points

Hi,

May I know the difference between PMOS LDO and NMOS LDO.

When to use PMOS LDO and when to use NMOS LDO.

Regards

Hari

over 7 years ago

0 Eric.Preiss over 7 years ago

TI__Expert 4435 points

Hi Hari,

PMOS LDO
Dropout is smaller at higher Vout, where Vsg (source-gate voltage) of the PMOS pass FET is higher.
LDO has a control loop pole dependent on the load (Cout and Iout).

NMOS LDO
Dropout is smaller at lower Vout, where Vgs (gate-source voltage) of the NMOS pass FET is higher.
May require a bias voltage > Vin for the error amplifier. This can be from an external Bias pin (if available on the LDO) or from an internal charge pump. A charge pump will increase the quiescent current of the LDO and contribute to LDO output noise.

More details can be found here:
www.ti.com/.../sbva026e.pdf
www.ti.com/.../slva072.pdf
www.ti.com/.../slva079.pdf
www.ti.com/.../slva068.pdf
www.ti.com/.../snva558.pdf
www.ti.com/.../snva020b.pdf

0 Hari T O0 over 7 years ago in reply to Eric.Preiss

Genius 3820 points

Hi Eric,

Thank you for your time.
Can we say when the I/P voltage is higher(Let it be greater than 2.5V) we will go for PMOS LDO's and when I/P voltage is low(Let it be 1V) we will
go for NMOS LDO's. Please correct me if I am wrong.

Regards
Hari T O

0 Eric.Preiss over 7 years ago in reply to Hari T O0

TI__Expert 4435 points

Hi Hari,

The pass element topology: PMOS, NMOS or Bipolar, is usually not the primary factor in choosing an LDO. I recommend choosing an LDO that will suit your application based on published specs in the datasheet.

Power management

Power management forum

Difference between PMOS LDO and NMOS LDO