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LDO Voltage Regulators for Battery-Powered ESP32 Products

INTRODUCTION

When we think about IoT and home automation, we look at modular and compact devices, sensors, microcontrollers, etc. Recently, the ESP32 microcontrollers have gained traction in the electronic world, especially in the IoT field. This device has multiple features such as inbuilt WIFI, Bluetooth modules, and sensors. The ESP32 microcontroller runs on a 3.3V voltage supply. When we power it externally using a power source either through a USB or battery, we need to regulate the voltage to 3.3V. The commonly used voltage regulators are the LDO (low-dropout) voltage regulator. In this article, we will be discussing the characteristics we need to account for when choosing an LDO voltage regulator, typically in the case of an ESP32. We will also be comparing the features of the commonly used and available regulators in the market.

Let’s discuss what are LDO voltage regulators?

(Low-dropout) LDO voltage regulators are linear regulators producing a steady low voltage(V), using the excess energy to heat, V(input)> V(output). We need to keep in mind some characteristics before we can choose the right regulator needed in the case of ESP32. 

Circuit Diagram
  • Dropout voltage
  • Current output
  • Quiescent current
  1. Dropout Voltage (VDO)

The minimum difference from the input to output voltage for the regulator to work is known as the dropout voltage. 

V(in)>V(out)+V(dropout)

In the case of ESP32, it has a working voltage of 3.3V. Hence, we need it as low as possible, since the battery voltage drops from (4.2V to 3.5V), and the ideal dropout voltage should be 0.2V. The regulator having such low dropout voltage is expensive and won’t be readily available. We need to look at the viable options close to the ideal range.

  1. Current output (Io)

The current output is the current requirement needed based on the application in use. In our case it’s the ESP32, the microcontroller consumes solely about 240-250 mA along with additional peripherals sensors attached we need to take into account the added current consumption to be around 500 mA. Now we know the current output needed for this application lies around 500mA.

  1. Quiescent current (Iq)

The current consumed by the regulator IC to work is known as quiescent current. This current is drawn when no load is connected to the regulator’s output. Generally, we expect the quiescent current to be lower than the application usage. In the case of ESP32, the deep sleep power consumption ranges from (mA-uA) so the most ideal option would be to use a regulator having a quiescent current in (uA), this would increase the battery life to a great extent.

Now, let’s discuss what voltage regulator options are available in the market available. The IC names mentioned here have been curated and compiled here: AMS1117, ME6211, MIC5219, AP2112, NCP1117, MCP1825, LP5912, LDK130M, HTC7333. 

From the mentioned ICs we will choose 5 of them and identify the best option for our application in the table below.

S. NoRegulator ICDropout Voltage(VDO)Output Current (Io) Quiescent current (Iq)
1AMS11171.1-1.25 V1 A5-13 mA
2ME62110.65 V600 mA50 uA
3MIC52190.6 V500 mA0.05-8 uA
4LP59120.25 V500mA30 uA
5LDK130M0.2-0.4 V300 mA0.1-30 uA
Comparison Table

From the regulators displayed in the table, the most commonly used ones are AMS1117 being readily available and comparatively cost-effective. But we can see better options up there in the table. We are looking at a regulator having around 500mA or greater, low dropout voltage, and low quiescent current. Anything with a quiescent current in (uA) is good with a dropout voltage close to 0.2V. We see that the LP5912 is the best fit for this application. In conclusion, we can say that we have learned what voltage regulators are, the main characteristics to look out for, and identify one based on the application, in specific the ESP32.

If you are looking for more information you can visit, and go through their datasheets for specific requirements.

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