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Choosing an appropriate LDO for low power device

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rookie:
I am building a wireless device that is expected to work off of a lipo battery. to power the mcu/peripherals, I need a regulator and hence started looking at different devices available in the market. I am interested in a well performing LDO that can get the most out of my battery. I found a few devices and am looking to narrow down on one or two that I can test. My current requirement is Iout = 150mA and Vout = 3.3V
I am sharing some of my rationale for selecting from these devices, so may be someone can poke holes in my reasoning and help me make a better decision! I'm no EE guy, but this is my analysis based on spending some time reading basics of LDO and respective datasheets:


MCP1810 - marketed as lowest quiescent current ldo in the market by microchip:
(section 1.0 of datasheet)
Iq = 20nA typical
Ignd = 200uA at 150mA
Vdropout = 380mV at 150mA
PSRR = 40dB(100Hz)

MCP1811 - another low Iq LDO from microchip
(section 1.0 of datasheet)
Iq = 250nA typical
Ignd = 90uA at 150mA
Vdropout = 400mV at 150mA
PSRR = -50dB(1kHz)

TPS783 - These LDOs are from TI, one of their lowest Iq offerings.
(section 6.5 of datasheet)
Iq = 420nA typical
Ignd = 8uA at 150mA
Vdropout = 130mV at 150mA
PSRR = 20dB (100Hz), 15dB (1kHz)

NCP170 - These are low Iq offerings in IOT space from ON Semi
(page 9 of datasheet)
Iq = 500nA typical
Ignd = could be atleast as high as 100uA at 150 mA from figure 20 for Vout = 3.6
Vdropout = 180mV at 150mA
PSRR = 41dB (1kHz)

STLQ020 - Again, IOT oriented LDOs from STMicro. This one is actually 200mA Iout:
(section 5 of datasheet)
Iq = 400nA typical
Ignd = 100uA at 200mA
Vdropout = 160mV at 200mA
PSRR = 50dB(100Hz), ~ 34dB(1kHz)


Most these devices seem to work well with input/output caps and are available in small form-factors. Even though I could choose the device with the lowest Iq, my device is not going to consume 0 current even on standby, so other parameters will definitely matter. So here are my thoughts on the devices:

Even though the microchp LDO MP1810 has the lowest Iq, it seems to get beat in dropout voltage and Ignd.

The STMicro device still has higher Ignd even with low Iq and low dropout voltage.

The OnSemi device still has relatively high Ignd with comparable Iq and dropout voltage.

To me, the TI device has the decent specs in most departments and something I'm leaning towards - low Iq (not lowest), low dropout and really seems to win in the Ignd. Although I'm not sure how much that varies with Vout, I think their datasheet says 2.2V for the stated Ignd.

So what do y'all think?

SiliconWizard:
From experience, depending on your input power source, I would avoid the NCP170. Those regulators tend to overshoot when the input voltage is rising (depending on rate and current draw at the output), so in some particular situations you could fry something. I really didn't like those LDOs.


mariush:
Well, there's a problem here.

I am interested in a well performing LDO that can get the most out of my battery.

By design, a LDO takes an input voltage and gives an output voltage, throwing out the difference as heat. So no matter what LDO you may choose, it would be anything but efficient.

For example, if your input voltage is 4v, your regulator's efficiency will be 600mW in +quiescent current , 495mW out (3.3v x 150mA)... you get a 82.5% efficiency.

With such low efficiency, thinking about a small quiescent current is kinda silly.

The smarter thing would be to use a switching regulator to get higher efficiency. If voltage stability is really important, you may consider adding a LDO at the output... for example output 3.5v with your switching regulator, then output 3.3v with your LDO.

A Micrel / Microchip  MIC23050 is over 90% (89% at 1mA output) efficient and at around 200mA it gets close to 93% efficient: http://ww1.microchip.com/downloads/en/DeviceDoc/mic23050.pdf
... and it's cheap, at around 0.4$ in 25pcs.



If you want something easier to solder, PAM2301 from Diodes Inc is a decent choice. Not quite as efficient as the above, but can still go above 85% and gets better the closer your input voltage is.



The inductors can be very small, surface mount ceramics, because the above regulators work at 4 Mhz and 1.5Mhz (for the PAM2301)... so the capacitors on the output can also be ceramic and a tiny capacitance is enough.

There's also MCP1603 from Microchip, which claims above 92% efficiency ... 2 Mhz switcher : http://ww1.microchip.com/downloads/en/DeviceDoc/22042B.pdf  (see Figure 2-13, page 9)

rookie:
@SiliconWizard , @mariush - Thanks for the suggestions!

@mariush - I have considered switching regulators and will certainly try out your suggested parts. There is also MAX38640 that seems really promising. The only reason I shy away from switching is that I don't have enough confidence working with them, and their effects on other components in the system like sensors, analog circuitry etc, let alone the wireless part itself! But the only way to learn is to actually try it out. I am limited by real estate, so I will have to think hard about incorporating a buck converter+ldo

Jan Audio:
R-7833

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