Skip to main content

Maximise on the Benefits of Using Ultra Low Dropout Regulators

onsemi Ultra Low Dropout Linear Regulators (LDOs) won’t leave your power tree in limbo.

onsemi new Ultra Low Drop Out LDO technology continues to push the limits and allows a rethink on power tree designs. The timing is perfect with so many circuits requiring multiple low voltage rails to supply the myriad of loads today, creating a simple yet efficient system has become daunting.  Ultra Low Drop Out Linear Regulators (LDOs) help simplify solutions by optimizing voltages, distributing the loads and minimizing the power dissipation normally associated with linear regulation.

These LDOs, like the NCP59748, and NCP133 have Ultra Low drop out voltages and allow the ripple rejection benefits of an LDO with the low power dissipation normally associated with a load switch.

Part

Max Iout

Drop out (typ) @ rated current / 25°C

Power Dissipation @ Vdo and Max Iout

NCP120

150 mA

30mV

4.5mW

NCP130

300 mA

60mV

18mW

NCP133

500 mA

100mV

50mW

NCP59748

1.5 A

37mV

55mW

Standard LDO

~500 mA

260 mV

130 mW

Efficiency will depend on the output voltage Vout, however, for a common 1.2Vout the efficiencies are >90% (assumes Vin is set near Vout + Vdo).

Two traditional methods for simultaneously powering both 1.2V and 1.1V power rails for an Audio CODEC or similar low voltage load are shown below.

title

title

LDOs use fewer external components by using an Ultra-Low Drop Out Linear Regulator a smaller and simpler solution with very good efficiency is possible. This configuration is shown below.

title

How low can the drop out voltage go?  Since the Vdo is dependent on the load current (Iout) and the internal NMOS FET RDSon, it is important to realize that often the ideal LDO may be rated for much higher maximum current.  It is important to look at the Dropout vs Iout Curves like this one for the NCP59748:

title

With an effective RDSon of ~25mOhms, for low current loads (

ON Semiconductor range of Ultra Low Dropout family of devices are shown in the table below. 

Part

Max Iout

Vdo (typ) @ rated current

Pd @ Vdo and Max Iout

“Effective RDSon”

Dropout at Iout = 100mA

NCP120

150 mA

30 mV

4.5 mW

200 mOhm

20 mV

NCP130

300 mA

60 mV

18 mW

200 mOhm

20 mV

NCP133

500 mA

100 mV

50 mW

200 mOhm

20 mV

NCP59748

1.5 A

37 mV

55 mW

  25 mOhm

2.5 mV

Standard LDO

~500 mA

260 mV

130 mW

520 mOhm

150 mV

These new family of LDOs allow you to “buck” down efficiently and get the LDO Linear Regulator benefits for simple, clean power.

Click here for the NCP133AMXADJTCG  RS 8427854

Click here for the NCP59748MN1ADJTBG RS 8270608

Narrowboat support services including maintenance, route planning, navigation and providing web content.
DesignSpark Electrical Logolinkedin