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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.
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.
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:
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.