Tag Archives: LDO

Versatile And Open Source LiPo bBattery Breadboard Power Supply

Orlando Hoilett from Calvary Engineering LLC designed a  versatile Li-Po battery breadboard power supply and wrote an Instructables on it. This power supply outputs 3.3V to the breadboard and takes input from a single-cell LiPo battery. The breadboard power supply also has the ability to charge the battery without needing to separate it from the circuit board. More importantly, this project is licensed under Open Source Hardware which means anyone can modify, distribute, make, and sell this design.

LiPo bread board power supply
LiPo breadboard power supply

Key Components

The complete BOM is available at the GitHub repository.

  • JST connector
    This connector connects directly to the LiPo battery.
  • 3.3V regulator, AP2210K
    3.3V logic is getting increasingly popular among electronics hobbyists and engineers. Also, boosting 3.7V of a LiPo battery to 5V can induce quite a bit of switching noise on the power supply. Linearly converting 3.7V to 3.3V is the best way to avoid this problem.
  • Battery Charger, MCP73831T
    This power supply has a charger built into the board so you can charge the battery without removing it from the power supply.
  • Voltage Selection Jumper
    The voltage selection headers are 3 pin male headers and they are labeled as 3.3V (or VReg) and VRAW (or LiPo). Connect the center pin to 3.3V to get power from the regulator. Connect the center pin to VRAW to get power directly from the LiPo battery.
  • DPDT Switch
    This switch lets you power down the board without removing the battery.
  • LED indicators
    LEDs are used to indicate the current status of the board.


This board breaks out the LiPo battery to the breadboard power rails on both sides. It has a DPDT switch to power down the board. The AP2210K IC has an ENABLE pin which is pulled down to the ground using the DPDT switch in order to enter the low power mode. In low power mode, the regulator and all the LEDs get disabled and draws almost no current from the LiPo. More about the AP2210K regulator IC is on this datasheet.

LiPo breadboard power supply schematic
LiPo breadboard power supply schematic

Another great feature of this breadboard power supply as mentioned earlier is, it incorporates an MCP73831T LiPo battery charger IC. It is a widely used PMIC (power management integrated circuit) for charging LiPo batteries. The LiPo battery should be connected to pin 3 (VBAT) and 5V should be applied to pin 4 (VDD).

The chip starts charging as soon as it detects 5V input and stops charging when the battery is full. Charging current is limited to USB standard i.e. 100mA by connecting a 10.2K resistor between pin 5 (PROG) and ground. So, it’s completely safe to charge the battery from your laptops USB port. Other host microcontrollers can check the battery status using pin 1 (status pin) of MCP73831T.

Ultra-low-noise, high PSRR, 0.5A negative rail LDO

By Graham Prophet @ eedesignnewseurope.com:

Analog Devices has added to its range of linear voltage regulator chips intended for stabilising supply rails to the most noise-sensitive active devices such as ADCs, DACs and precision/instrumentation amplifiers, that operate from negative voltage rails.

Ultra-low-noise, high PSRR, 0.5A negative rail LDO – [Link]

LDO regulator boasts high PSRR


by Susan Nordyk @ edn.com:

In addition to low noise, the LT3045 linear regulator from Linear Technology provides a PSRR (power supply rejection ratio) of >90 dB to 10 kHz and >70 dB to 2.5 MHz, quieting noisy or high-ripple input supplies. The LDO regulator’s ultralow spot noise of only 2 nV/√Hz at 10 kHz and RMS noise of just 0.8 µVRMS from 10 Hz to 100 kHz make it well-suited for noise-sensitive applications, such as PLLs, VCOs, instrumentation, and medical equipment.

LDO regulator boasts high PSRR – [Link]

LT3086 – 40V, 2.1A Low Dropout Adjustable Linear Regulator with Monitoring and Cable Drop Compensation


Graham Prophet  @ www.edn-europe.com discuss about LT3086 LDO.

The 40V, 2.1A low dropout linear regulator (LDO) includes current monitoring with externally settable current limit and temperature monitoring with external control of thermal limit temperature. The device includes a programmable power-good status flag, cable drop compensation and easy paralleling. The current reference in the LT308x LDO family provides regulation, independent of output voltage.

Benefits of Using A Buck-Boost Converter As A Pre-regulator For LDOs

Intersil published a new white paper titled “Preventing Subsystem Brownouts in Mobile Devices“. This white paper demonstrates the benefit of using a buck-boost converter as a pre-regulator, which leads to better overall system efficiency and enhanced battery life.


Systems powered from a battery may have voltage brownout when they are subjected to a burst current discharge, that is because of internal resistance of the battery. The internal resistance in Li-Ion battery varies according to its charging level. It can reach 200 Milli-ohm at the end of the discharge. Thus, a 4A burst current can cause an 800mV droop at the terminal, pushing the nominal 3.4V voltage to 2.6V, which is considered as a brownout voltage if the target LDO output is 2.85V. In this case boost converters prevent the momentary brownout.

Overall system efficiency is another useful aspect of using a buck-boost converter as a pre-regulator. The battery voltage is first converted to a voltage slightly higher than the highest LDO output voltage of the target LDOs, which is typically 3.3V. The buck-boost output is then set to 3.4V. So, the LDOs see a 3.4V input voltage, regardless of the battery voltage.

We can see, by numbers, the improvement of efficiency by comparing the two setups, with and without using the buck-boost converter.



The figure below shows the comparison of battery discharge with and without a pre-regulator, while running the same applications with the same battery. You can see 12% enhancement to battery life.


[White Paper]

How to Improve Buck Converter Light Load Efficiency with an LDO


By Michael Hartshorne @ digikey.com:

Designing a DC/DC converter that only consumes micro amps of current at no load can be compared to fueling a muscle car with lighter fluid – you may get it to work, but it won’t be easy. High efficiency at full load currents is commonplace in most modern DC/DC converters; however, achieving high efficiency when the load is disabled or disconnected is still a difficult and/or expensive task.

How to Improve Buck Converter Light Load Efficiency with an LDO – [Link]

Choose the right step-up/down voltage regulator for portable applications


Reno Rossetti & Inyong Kim discuss about the power needs on portable devices and help us choose the right regulator.

A popular power source for portable devices is a single lithium-ion cell with 4.2V at full charge and 2.8V at end of discharge. However, some functions within portable electronics, such as a SIM card and DSP, require 2.8V and 3.3V. These are normally provided by low noise LDOs. The LDOs inputs (VCC) must be at a slightly higher voltage than the highest LDO output. Hence, VCC ends up right in the middle of the lithium-ion battery’s range of operation.

Choose the right step-up/down voltage regulator for portable applications – [Link]

LT3091 – –36V, 1.5A Negative Linear Regulator with Programmable Current Limit


Linear Technology Corporation announces the LT3091, the latest addition to our LDO+ family, a 1.5 A low dropout negative linear regulator featuring low noise, rail-to-rail operation, precision programmable current limit and a bidirectional output current monitor. The device is cable-drop compensation capable, easily paralleled for higher current or circuit board heat spreading, and configurable as a 3-terminal floating regulator. The LT3091’s input voltage range is –1.5 V to –36 V. A single resistor programs the adjustable rail-to-rail output voltage from 0 V to –32 V and dropout voltage is only 300 mV (typical at full load).

LT3091 – –36V, 1.5A Negative Linear Regulator with Programmable Current Limit – [Link]

LT3091 – –36V, 1.5A Negative Linear Regulator with Programmable Current Limit


The LT®3091 is a 1.5A, low dropout negative linear regulator that is easily paralleled to increase output current or spread heat on surface mounted boards. Designed with a precision current reference followed by a high performance rail-to-rail voltage buffer, this regulator finds use in applications requiring precision output, high current with no heat sink, output adjustability to zero and low dropout voltage. The device can also be configured as a 3-terminal floating regulator.

LT3091 – –36V, 1.5A Negative Linear Regulator with Programmable Current Limit – [Link]


MC34VR500V1ES Multi-Output DC/DC Regulator

The circuit in this reference design features the capability of MC34VR500V1ES to supply multiple DC voltage outputs. This device is designed to support the LS1/T1 family of communication processors, which require efficient and precise level of voltage supplies. With its four switching and five linear regulators, the MC34VR500V1ES can supply power to the whole system, e.g., the processor, memory, system peripherals.

The MC34VR500V1ES device runs with a supply voltage ranging from 2.8V to 4.5V. It can provide nine outputs. Four of these outputs (SW1-4) are buck regulators while the rest (LDO1-5) are general purpose LDOs. Each one of the buck regulator is capable of operating in Pulse Frequency Modulation (PFM), Auto Pulse Skip (APS), and Pulse Width Modulation (PWM) switching modes. These buck regulators also have a current limit feature that generates a fault interrupt whenever there is an overcurrent condition. The SW1 output is capable of providing 0.625-1.875V/4.5A supply while SW2 and SW3 can provide 0.625-1.975V/2A and 0.625-1.975V/2.5A, respectively. The SW1, SW2 and SW3 voltages can be varied with a step size of 25mV. The SW4 output is half of the voltage output of SW3. The general output LDOs can output voltages ranging from 1.8-3.3V with a step size of 100mV except for LDO1 which can only give 0.8-1.55V output with 50mV step size. The LDO1 output can provide current up to 250mA, while LDO2 and LDO4 can output up to 100mA only. The LDO5 output can provide 200mA of current while LDO3 can output up to 350mA. Aside from these nine outputs, the MC34VR500V1ES also have a REFOUT output dedicated for DDR memory reference voltage. The voltage of this REFOUT output is usually half of the SW3 output and can only provide up to 10mA of current. The MC34VR500V1ES outputs can be changed by programming it via the I2C interface.

The operation of the MC34VR500V1ES can be reduced to four states, or modes: ON, OFF, Sleep, and Standby. For the device to turn ON, the input voltage must surpass a voltage threshold of 3.1V, the EN pin must be high, and PORB is de-asserted. The 34VR500 enters the OFF mode when the EN pin is low or there is a thermal shutdown event that forces the device into the OFF mode. Standby mode is usually entered when the STBY pin is asserted for low-power mode of operation. The device only goes into sleep mode if the EN pin is de-asserted. To exit sleep mode, assert the EN pin.

MC34VR500V1ES Multi-Output DC/DC Regulator – [Link]