By Ashok Bindra:
The use of low-dropout regulators, popularly known as LDOs, is common in many applications today because they provide a simple and inexpensive way to regulate an output voltage that is stepped-down from a higher input voltage. In addition, linear LDO voltage regulators contribute very-low noise as compared to switching regulators.
Nonetheless, to keep system power consumption low, such regulators must also feature ultra-low quiescent current (IQ) while providing excellent dynamic performance to ensure a stable, noise-free voltage rail, suitable for driving IC loads such as microprocessors, FPGAs, and other devices on the system board.
Selecting the Right Ultra-Low Quiescent-Current LDO Regulator - [Link]
The LT8614 is a 4A, 42V input capable synchronous step-down switching regulator. A unique Silent Switcher architecture reduces EMI/EMC emissions by more than 20dB, well below the CISPR 25 Class 5 limit. Even with switching frequencies in excess of 2MHz, synchronous rectification delivers efficiency as high as 96% while Burst Mode operation keeps quiescent current under 2.5μA in no-load standby conditions. Its 3.4V to 42V input voltage range makes it ideal for automotive and industrial applications.
LT8614 – 42V, 4A Synchronous Step-Down Silent Switcher with 2.5μA Quiescent Current - [Link]
This is a DC-DC step-up converter based on LM2585-ADJ regulator manufactured by Texas Instruments. This IC was choosen for it’s simplicity of use, requiring minimal external components and for it’s ability to control the output voltage by defining the feedback resistors (R1,R2). NPN switching/power transistor is intergrated inside the regulator and is able to withstand 3A maximum current and 65V maximum voltage. Switching frequency is defined by internal oscillator and it’s fixed at 100KHz.
LM2585 12V to 24V @ 1A Step-up switching regulator - [Link]
The LTC®3607 is a 15V dual 600mA monolithic synchronous step-down regulator which has only 55μA quiescent current. Intended for a variety of applications, including dual lithium-ion battery products, it operates from a wide 4.5V to 15V input voltage range. It features a constant 2.25MHz switching frequency, enabling the use of tiny, low cost capacitors and inductors 1mm or less in height. Each output voltage is adjustable from 0.6V to VIN. The internal synchronous power switches provide high efficiency without the need for external Schottky diodes.
LTC3607 – Dual 600mA 15V Monolithic Synchronous Step-Down DC/DC Regulator - [Link]
The TS3310 is a low power boost converter with an industry-leading low quiescent current of 150nA, enabling ultra long battery life in systems operating from a variety of battery sources. The TS3310 is the industry’s only boost converter to specify its no-load supply current with an actively switching boost engine, providing a more accurate picture of supply current during normal operation. The TS3310 boosts input voltages from 0.9V-3.6V to one of eight user-selectable output voltages ranging from 1.8V to 5.0V. The TS3310 includes two outputs: (a) an always-on primary output and (b) a user-enabled, load-switched secondary output designed to power burst-on loads operating at low duty cycles, such as a ZigBee radio.
TS3310: A True 150-nA IQ, 0.9-3.6VIN, Selectable 1.8-5VOUT, High-Efficiency Instant-ON™ Boost Converter - [Link]
The LT3690 is an adjustable frequency monolithic buck switching regulator that accepts input voltages up to 36V. A high efficiency 90mΩ switch is included on the device along with the boost diode and the necessary oscillator, control, and logic circuitry. The internal synchronous power switch of 30mΩ increases efficiency and eliminates the need for an external Schottky catch diode. Current mode topology is used for fast transient response and good loop stability. Shutdown reduces input supply current to less than 1μA. The low ripple Burst Mode maintains high efficiency at low output currents while keeping output ripple below 15mV in typical applications.
LT3690 – 36V, 4A, 1.5MHz Synchronous Step-Down Switching Regulator with 70μA Quiescent Current- [Link]
International Rectifier introduced the IR3823 SupIRBuck integrated voltage regulator designed for space-constrained, energy efficient netcom, server and storage applications. Steve Taranovich writes:
The IC delivers up to 3A a 3.5×3.5mm package. Efficiencies in excess of 97.5% are obtainable for designs converting power from a 6V input to a 4.8V output. The extremely high initial efficiency allows switching at up to 1.5MHz from a 12V supply to enable a complete 3A power supply solution in less than 130mm2. Featuring constant frequency and virtually jitter-free operation with synchronization capability, the new device is well suited to noise-sensitive applications, while the higher bandwidth reduces component count to shrink PCB footprint. A tri-level selectable soft-start feature is also offered for ease of sequencing.
IR’s integrated voltage regulator with 97.5% efficiency in a 3.5×3.5mm package - [Link]
The LT®8610 step-down regulator integrates key high performance features in one compact IC. It offers synchronous rectification, for efficiencies up to 96%. The low quiescent current of 2.5µA extends battery life and saves extra circuitry. High speed switching minimizes board space and helps avoid EMI problems. A low dropout of 200mV at 1A load allows wide VIN range. The LT8610 is a great choice for many step-down applications requiring high input voltages up to 42V and load currents up to 2.5A.
High Efficiency, Ultralow IQ, 42V, 2.5A Sync Buck Regulator - [Link]
by Steven Keeping:
Traditionally, switching DC/DC converters (voltage regulators) were controlled using analog techniques because these were simple to implement and helped to maximize the power supply’s efficiency. Digital components were too slow and power greedy to challenge analog dominance.
However, over the past several years the introduction of high-speed, low power consumption and inexpensive silicon has rekindled interest in “digital power management.”
Armed with these new chips, designers are keen to take advantage of features such as the ease with which digital control enables optimization of the power supply by adaptation of a closed-loop response – even allowing adjustment “on the fly” to suit changes in the operating environment or to compensate for factors such as capacitive loading and component aging.
This article considers the benefits that digital power brings to voltage regulators by comparing an analog power supply with its digital equivalent. The article then continues by describing some of the latest digital regulators released by major vendors that take advantage of the control techniques discussed.
The Rise of Digital Control for DC/DC Regulation - [Link]
Steve Taranovich writes:
Touchstone, with its first analog power management product, has enhanced such a function with the capability to use supply voltages down to 0.6V while still being able to deliver a 75 mA output current.
The device can be used in power harvesting or peak load buffering applications, the LDO may post-regulate voltage buffered in a large capacitor or super-capacitor at boost’s output. Finally, the LDO may be operated simply as an on/off load switch.
TS3300 switching regulator coupled with an LDO in same package - [Link]