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]

Intersil’s Switching Regulators Adopted in Huawei P9 Smartphone


Intersil announces the adoption of its latest family of buck-boost switching regulators in one of Huawei’s newest smartphone. The ISL91110 buck-boost switching regulator powers the Huawei P9 smartphone’s key system peripherals providing excellent efficiency and performance. [via]

Intersil’s ISL91110 buck-boost switching regulator supplies power to key system peripherals in the P9 dual-camera smartphone, using a proprietary, fully synchronous four-switch architecture. This advanced architecture enables the seamless transition from buck to boost and delivery of up to 2.5A output current at the lowest single-cell Li-ion battery voltages to extend battery life.

We previously covered a member of this family. Check it here: ISL91128 – A New Buck-Boost Regulator With I2C Interface From Intersil

Intersil’s Switching Regulators Adopted in Huawei P9 Smartphone – [Link]

Adding ADC to Microcontrollers without ADC


@ show us how to interface an analog signal to a microcontroller that doesn’t have an ADC.

I recently had the need to carefully measure a voltage with a microcontroller which lacks an analog-to-digital converter (ADC), and I hacked together a quick and dirty method to do just this using a comparator, two transistors, and a few passives. The purpose of this project is to make a crystal oven controller at absolute minimal cost with minimal complexity. Absolute voltage accuracy is not of high concern (i.e., holding temperature to 50.00 C) but precision is the primary goal (i.e., hold it within 0.01 C of an arbitrary target I set somewhere around 50 C).

Adding ADC to Microcontrollers without ADC – [Link]

Analog front-end IC linearizes sensors


Susan Nordyk @ discuss about LTC2986 which is able to digitize and linearize a combination of temperature sensors in Celsius or Fahrenheit degrees.

A 10-channel temperature-measurement IC, the LTC2986 from Linear Technology directly digitizes any combination of thermocouples, RTDs, thermistors, and external diodes with 0.1°C accuracy and 0.001°C resolution. The analog front-end device combines three 24-bit delta-sigma ADCs with all the necessary excitation and control circuits for each sensor. On-chip EEPROM stores user configuration data and custom sensor coefficients, eliminating IC or sensor programming by a host processor.

The LTC2986 measures absolute microvolt-level signals from thermocouples and ratiometric resistance from RTDs and thermistors. It performs linearization and outputs the results in °C or °F. With 10 analog inputs, the LTC2986 accommodates up to 9 thermocouples, 4 RTDs, 4 thermistors, and/or 10 diodes, with support for Type B, E, J, K, N, S, R, and T thermocouples; 2-wire, 3-wire, and 4-wire RTDs; and 2.25-kΩ to 30-kΩ thermistors.

Analog front-end IC linearizes sensors – [Link]

MPPT Solar Charger Design based on PIC18F26J50


At the core of the design is a PIC18F26J50 in a 28 pin SOIC package. It’s capable of running at down to 2.15 volts and consumes extremely little power when running at lower clock speeds. And apart from that it features USB so we can have all the benefits of USB without any external components except, of course, a USB socket.

MPPT Solar Charger Design based on  [Link]

CO2, temperature and humidity monitor


An open source CO2 monitoring project from Roving Dynamics:

The project described below uses a MH-Z16 or MH-Z19 CO2 sensor and a DHT-22 (or DHT-11 if less accuracy is required) to measure the Temperature and Humidity. It has a 4 line by 20 character LCD Display to show the current readings and status, a warning alarm and two relays which can be triggered on a low CO2 (Generally above 1000 ppm) normally to switch on an extractor fan and a high level (4000 ppm) which will trigger a warning device such as an external alarm. There are two models I used the 0 to 5000 ppm device here but the code will be the same for the 0 to 10000 ppm model

CO2, temperature and humidity monitor – [Link]

Ultrasonic Anemometer Project Progress


In the mean time I managed to do some rudimentary testing and now feel confident to take orders. These tests concern the hardware only. What I said last time about the state of the software still applies. But let me tell you what I’ve been able to test so far.

Ultrasonic Anemometer Project Progress – [Link]


8 Channel Optically Isolated IO Board


Opto-Isolated I/O Board offers a compact & convenient way to interface industrial type inputs/outputs to your microcontroller boards, Signal transmission between circuits of different potentials and impedances etc.


  • 4 opto-isolated inputs & 4 opto-isolated outputs
  • Std TTL input signals for opto-couplers
  • Interfacing is via 10-pin Box Header and Screw terminal type connector
  • Power source LED indicator
  • Four mounting holes 3.2 mm each
  • PCB dimensions 54 mm x 64 mm

8 Channel Optically Isolated IO Board – [Link]

Ultra-low power, dual-band wireless microcontrollers from TI

Intended for tasks such as monitoring IoT networks from a handheld device, Texas Instruments’ latest series of microcontrollers are single-chip Sub-1 GHz plus Bluetooth low energy ICs. By Graham Prophet @

As part of TI’s pin-to-pin and software compatible SimpleLink ultra-low power platform, the SimpleLink dual-band CC1350 wireless MCU enables developers to move from a three-chip solution to a single chip, while reducing design complexity, saving power, cost and board space. The CC1350 wireless MCU offers a range of up to 20 km on a coin cell battery for building and factory automation, alarm and security, smart grid, asset tracking and wireless sensor network applications.

Ultra-low power, dual-band wireless microcontrollers from TI – [Link]

Infinite Noise True Random Number Generator


waywardgeek @ shares his USB TRNG:

The Infinite Noise TRNG is a USB key hardware true random number generator. It uses what I call a “Modular Entropy Multiplier” architecture (previously Infinite Noise Multiplier or FireBug). Besides being simple, low-cost, and fast, it is much easier to get right than other TRNGs. It naturally defends against influence from outside signals, such as radio interference and power supply noise, making it simple to build securely, without requiring an expert in analog design.

Infinite Noise True Random Number Generator – [Link]