Dual Synchronous Step-Down DC/DC Converter Delivers 95% Efficiency

Linear Technology recently announced the LT8616, a 42-V input capable, high-efficiency dual synchronous monolithic step-down switching regulator. Its dual channel design delivers independent 2.5- and 1.5-A continuous current to outputs as low as 0.8 V. A dual channel synchronous rectification topology delivers up to 95% efficiency while Burst Mode operation keeps quiescent current under 6.5 µA (both channels enabled) in no-load standby conditions, making it ideal for always-on systems. Switching frequency can be programmed from 200 kHz to 3 MHz and is synchronizable throughout this range.LT8616 Linear

The LT8616’s 35-ns minimum on-time enables 16 VIN to 1.8 VOUT step-down conversions, while switching at 2 MHz helps you avoid critical noise-sensitive frequency bands, such as AM radio while having a very compact solution footprint. Its 3.4- to 42-V input voltage range makes it ideal for automotive applications which must regulate through cold-crank and stop-start scenarios with minimum input voltages as low as 3.4 V and load dump transients in excess of 40 V. Each channel of the LT8616 maintains a minimum dropout voltage of only 400 mV (at 1 A) under all conditions, enabling it to excel in scenarios such as automotive cold-crank. The LT8616’s 28-lead thermally enhanced TSSOP package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LT8616 utilizes dual internal top and bottom high efficiency power switches with the necessary boost diodes, oscillator, control and logic circuitry integrated into a single die. Each channel switches 180° out-of-phase to reduce output ripple. Each channel has a separate input for added design flexibility. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15 mVPP. Unique design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the LT8616’s current-mode topology provides fast transient response and excellent loop stability. Other features include internal compensation, power good flags, output soft-start/tracking and thermal protection.

The LT8616 is available in a thermally enhanced 28-lead TSSOP package. Three temperature grades are available, with operation from –40°C to 125°C (junction) for the extended (E) and industrial (I) grades and a high temperature (H) grade of –40°C to 150°C. The 1,000-piece price starts at $4.15.

Features

  • 3.4 to 42 V Input voltage range
  • 5- and 1.5-A Buck regulators with separate inputs
  • Fast minimum switch on-time: 35 ns
  • Ultralow quiescent current burst mode operation
  • 180° Out-of-phase switching
  • Adjustable and synchronizable: 200 kHz to 3 MHz
  • Accurate 1-V Enable pin thresholds
  • Internal compensation
  • Output soft-start and tracking
  • TSSOP Package:
  • Thermally enhanced 28-lead TSSOP package

 

Compact 20A Hot Swap Controller Integrates MOSFET & Current Sensing

Linear Technology Corp. recently announced the LTC4234, a 20A Hot Swap controller with integrated MOSFET and current sensing, which provides a small footprint hot-plug solution for high-density circuit boards. The LTC4234 ensures safe board insertion and removal from live 2.9-to-15-V backplanes by controlling an internal N-channel power MOSFET to gently power up bulk capacitors and avoid sparks, connector damage and system glitches. By integrating the two most critical and largest Hot Swap components-power MOSFET and sense resistor, the LTC4234 reduces design time and saves board area. The internal, production-tested MOSFET’s safe operating area (SOA) is specified to ensure a rugged hot-plug solution, especially for space-constrained boards and cards in servers, network routers and switches, solid-state drives, and industrial systems.Linear LTC4234

Upon insertion, the LTC4234 waits for connector contact bounce to finish before soft-starting the output. A ground-referenced signal proportional to the load current is provided for monitoring with an external analog-to-digital converter (ADC). The current limit can be reduced from its 22.5A default with a single resistor, affording quick adjustment for dynamic load changes and various applications. For higher current applications, two LTC4234s are easily paralleled for a 40A solution. During overcurrent conditions, the controller limits MOSFET power dissipation by folding back its current limit for an adjustable timeout period. Undervoltage and overvoltage thresholds protect downstream loads against voltages outside a valid window, preventing circuit malfunction and damage.

The LTC4234’s features:

  • Enables safe board insertion
  • Integrated 4-mΩ MOSFET with sense resistor
  • Guaranteed safe operating area
  • Wide operating voltage range of 2.9 to 15 V
  • Current limit for overcurrent fault protection
  • Current and temperature monitor, power good & fault outputs
  • –40°C to 125°C Operating temperature range
  • 38-Pin 5 mm × 9 mm QFN Ppackage

The LTC4234 starts at $4.95 each in 1,000-piece quantities. Device samples and evaluation circuit boards are available online or from your local Linear Technology sales office.

Source: Linear Technology

 

 

60-V LED Driver with Internal 4-A Switch & PWM Generator

Linear Technology’s LT3952 is a current mode step-up DC/DC converter with an internal 60-V, 4-A DMOS power switch. It is specifically designed to drive high power LEDs in multiple configurations. It combines input and output current regulation loops with output voltage regulation to operate as a flexible current/voltage source.  The LT3952’s 3-to-42-V input voltage range makes it ideal for a wide variety of applications, including automotive, industrial, and architectural lighting.Linear 3952

The LT3952 can drive up to 16 350-mA white LEDs from a nominal 12-V input, delivering in excess of 15 W. It incorporates a high side current sense, enabling its use in boost mode, buck mode, buck-boost mode or SEPIC topologies. Internal spread spectrum frequency modulation minimizes EMI concerns. The LT3952 delivers efficiencies of over 94% in the boost topology, eliminating the need for external heat sinking, and internal LED short-circuit protection enables added reliability required in most applications. A frequency adjust pin permits the user to program the switching frequency between 200 kHz and 3 MHz, optimizing efficiency while minimizing external component size and cost. The LT3952 delivers over 90% efficiency while switching at 2 MHz in a tiny solution footprint. The LT3952 provides a very compact high power LED driver solution in a thermally enhanced TSSOP-28E package.

The LT3952 has a gate driver for a PMOS LED disconnect switch, delivering dimming ratios of up to 4,000:1 using an external PWM signal. For less demanding dimming requirements, the CTRL pin can be used to offer a 10:1 analog dimming range and an internal PWM generator can be used for 5:1 dimming. The LT3952’s fixed frequency, current-mode architecture offers stable operation over a wide range of supply and output voltages. Output short-circuit protection and open LED protection enhance system reliability. Other features include frequency synchronization, spread spectrum frequency modulation, programmable VIN undervoltage and overvoltage protection, and an input current limit and monitor.

The LT3952EFE is available in a thermally enhanced 28-lead TSSOP package. Three temperature grades are available, with operation from –40°C to 125°C (junction) for the extended, and industrial grades, and a high temperature grade of –40°C to 150°C. Pricing starts at $3.95 each in 1,000-piece quantities and all versions are available from stock. For more information, visit www.linear.com/product/LT3952

Source: Linear Technology

3.3-V/5-V 4-Mbps CAN Transceiver

Linear Technology Corporation introduces the LTC2875, an exceptionally rugged, high-voltage-tolerant controller area network (CAN) transceiver to greatly reduce field failures without the need of costly external protection devices. In practical CAN systems, installation cross-wiring faults, ground voltage faults or lightning induced surge voltages can cause overvoltage conditions that exceed absolute maximum ratings of typical transceivers. The LTC2875 features ±60-V overvoltage fault and ±25-kV HBM ESD protection on the data transmission lines, protecting bus pins during operation and shutdown. Whether a circuit is transmitting, receiving or powered off, the LTC2875 tolerates any voltage within ±60 V without damage, increasing the robustness of typical CAN networks.Linear LTC2875

CAN bus systems are becoming increasingly popular in industrial controls, instrumentation networks and automotive electronics. The CAN bus has a well defined protocol stack, with support for standalone controllers, FPGAs and ASICs, making implementation easier over alternative interfaces, such as RS-485. The LTC2875 provides the flexibility to be powered from a 3.3-V or 5-V rail, which is very useful in industrial applications where a 5V rail may not be present. In addition to the high fault and ESD protection, the device features a low electromagnetic emission (EME) driver with a transmit data (TXD) dominant timer to prevent faulty controllers from clamping the bus, as well as a high electromagnetic immunity (EMI) receiver with an extended ±36-V common mode range to enable operation in electrically noisy environments and in the presence of ground loops. The LTC2875 features a high speed data rate of 4 Mbps with an adjustable slew rate for data rates as low as 1 kbps. A shutdown mode brings all of the LTC2875’s outputs to high impedance and reduces power consumption to 1 µA.

The LTC2875 is offered in commercial, industrial, automotive and military (–55°C to 125°C) temperature grades and is available in 3 mm × 3 mm DFN-8 and SO-8 packages, with industry-standard pinouts.

Pricing starts at $1.72 each in 1,000-piece quantities.

Source: Linear Technology

20-A Step-Down µModule Regulator Optimized for Low VIN to Low VOUT Conversion

Linear Technology Corp. recently introduced the LTM4639, which is 20-A DC/DC step-down µModule (micromodule) regulator. According to Linear, the regulator can convert “2.5 to 7 V main-power system rails to point-of-load voltages as low as 0.6 V.”

Linear Technology LTM4639

Linear Technology LTM4639

The LTM4639—which includes an inductor, DC/DC controller, MOSFETs, and compensation circuitry—is housed in a 4.92-mm BGA package with a 15 mm × 15 mm footprint. For 3.3-V input to 1.5-V output conversion at 20-A load, efficiency is 88%, power loss is 3.9 W, and junction temperature rise above ambient temperature is 37°C. The micromodule regulator provides a precise output voltage regulation. Up to four devices can be paralleled for up to 80-A output while operating out-of-phase to reduce the number of input and output capacitors.

The LTM4639’s input supply range is 2.375 to 7 V. For operation from 3.3 V and lower, a 5-V, low-power auxiliary supply is needed to bias internal circuitry. Output voltage ranges from 0.6 to 5.5 V with protection functions for overcurrent and overvoltage conditions.

The LTM4639 is rated for operation from –40°C to 125°C. The 1,000-piece price is $19.45 each.

Source: Linear Technology

Linear Ultrathin 1.8-mm, 3A µModule Regulator

Linear Technology Corp. recently announced the LTM4623 3A µModule (micromodule) step-down regulator in an ultrathin 1.8-mm profile LGA package with only a 6.25 mm × 6.25 mm footprint. With solder paste, the package height is less than 2 mm, meeting the height restrictions of many PCIe, Advanced Mezzanine Cards (AMC) for AdvancedTCA carrier cards in embedded computing systems. The small size and low height allow the LTM4623 to be mounted on the backside of the PCB, freeing space on the topside for components such as memory and FPGAs.linearLTM4623

The LTM4623 operates from 4-to-20-V input supplies and precisely regulates an output voltage from 0.6 to 5.5 V with 1.5% maximum total DC output voltage error. Application examples include ultra-dense data storage, gateway controllers, and 40-to-100-Gbps network equipment.

The LTM4623 solution fits in a 0.5 cm2 dual-sided PCB or less than 1 cm2 on a single-sided PCB. The circuit only requires one input capacitor and one output capacitor, a resistor to set VOUT, and a small capacitor for VOUT tracking and soft-start. With an auxiliary 5-V bias, the LTM4623 operates from input supplies as low as 2.375V. The operating efficiency for converting 12 VIN to 1.5 VOUT and 3.3 VOUT at 3A is 80% and 88%, respectively. Power loss for 12 VIN to 1.5 VOUT is 1.1 W, resulting in only a 24°C rise in junction temperature. The LTM4623 is rated for operation from –40°C to 125°C.

One thousand-piece pricing starts at $6.05 each.

Source: Linear Technology

Linear Battery Charger with Multi-Chemistry Operation

Linear Technology Corp. recently introduced the LTC4079, which is a 60-V, constant-current/constant-voltage, 250-mA multi-chemistry battery charger. According to Linear, its “low quiescent current linear topology offers a simple inductorless design and accepts a wide 2.7 V to 60 V input voltage range.”LinearLTC4079

 

The LTC4079’s features, characteristics, and capabilities include:

  • A resistor-programmable 1.2- to 60-V battery charge voltage range with ±0.5% charge voltage accuracy
  • Adjustable charge current from 10 to 250 mA with an external resistor
  • A low-profile (0.75 mm) 10-pin 3 mm x 3 mm DFN package with backside metal pad for excellent thermal performance.
  • Guaranteed foperation from –40°C to 125°C in both E-and I-grades.
  • One thousand-piece pricing starts at $2.35 each for the E-grade.

Source: Linear Technology

LTC2946 Wide-Range I2C Power, Charge, and Energy Monitor

Linear Technology Corp. recently introduced the LTC2946, which is a high- or low-side charge, power and energy monitor for DC supply rails in the 0-to-100-V range. According to Linear Technology’s release:

An integrated ±0.4% accurate, 12-bit ADC and external precision time base (crystal or clock) enables measurement accuracy better than ±0.6% for current and charge, and ±1% for power and energy. A ±5% accurate internal time base substitutes in the absence of an external one. All digital readings, including minimums and maximums of voltage, current and power, are stored in registers accessible by an I²C/SMBus interface. An alert output signals when measurements exceed configurable warning thresholds, relieving the host of burdensome polling for data. The LTC2946 provides access to all the necessary parameters to accurately assess and manage board level energy consumption. In addition its wide operating range makes it ideal for monitoring board energy consumption in blade servers, telecom, solar and industrial equipment, and advanced mezzanine cards (AMC).

Source: Linear Technology

Source: Linear Technology

The LTC2946’s features include

  • 0 to 100 V Monitoring Range; greater than 100 V with internal shunt regulator
  • 12-Bit ADC with Scan and Snapshot Modes
  • I²C/SMBus digital interface
  • Guaranteed Accuracy: ±0.4% for 12-bit voltage; ±0.6% for 12-bit current and 32-bit charge; and ±1% for 24-bit power and 32-bit energy
  • Internal ±5%, external or crystal time bases
  • Minimum and maximum value recorder
  • Bias Supply Range: 4 to 100 V, or 2.7 to 5.9 V
  • Alerts on exceeding warning thresholds
  • Split SDA eases optoisolation
  • Shutdown Mode with IQ < 40 µA
  • 16-pin MSOP and 4 mm × 3 mm DFN Packages

Source: Linear Technology

Linear LT3999 DC/DC Transformer Driver

Linear Technology recently launched the LT3999 monolithic push-pull isolated DC/DC transformer driver with two 1-A current limited power switches. It operates over an input voltage of 2.7 to 36 V and is targeted for power levels up to 15 W, making it a good option for a variety of industrial applications.

Source: Linear Technology

Source: Linear Technology

The LT3999’s features include:

  • Wide VIN range: 2.7 to 36 V
  • Dual 1-A switches
  • Programmable switching frequency: 50 kHz to 1 MHz
  • Synchronizable to an external clock up to 1 MHz
  • Duty cycle control for output voltage regulation
  • Low noise topology
  • Programmable input over- and under-voltage lockout
  • Cross-conduction prevention circuitry
  • Extended and industrial grades: –40° to 125°C operating junction temperature
  • Automotive temperature grade: –40° to 150°C operating junction temperature
  • Military temperature grade: –55° to 150°C operating junction temperature

The LT3999’s 1,000-piece price starts at $2.75 each for the E-grade.

Source: Linear Technology

 

LT8580 Boost/SEPIC/Inverting DC/DC Converter

Linear Technology Corporation recently announced the availability of the LT8580 current-mode, fixed-frequency, step-up DC/DC converter with an internal 1-A, 65-V switch. Operating from an input voltage range of 2.55 to 40 V, you’ll find the LT8580 useful for a variety of applications with input sources ranging from a single-cell Li-Ion to automotive inputs.

Source: Linear Technology

Source: Linear Technology

Key points:

  • Configurable as either a boost, SEPIC or an inverting converter
  • 3 mm × 3 mm DFN package (or MSOP-8E) and tiny externals
  • Low VCESAT switch (0.4 at 0.75 A) delivers efficiencies of up to 86%
  • User-adjustable UVLO

Pricing starts at $2.35 each for 1,000-piece quantities.

Source: Linear Technology

100-V Forward Voltage Controller

Linear Technology recently announced the LT8310, which is a resonant-reset forward converter controller that drives an external low side N-channel MOSFET from an internally regulated 10-V supply. The LT8310 features duty mode control to generate a stable, regulated, isolated output using a single power transformer. With the addition of output voltage feedback, via optocoupler (isolated) or directly wired (nonisolated), current mode regulation is activated, improving output accuracy and load response. A choice of transformer turns ratio makes high step-down or step-up ratios possible without operating at duty cycle extremes.

Source: Linear Technology

Source: Linear Technology

The switching frequency is programmable from 100 kHz to 500 kHz to optimize efficiency, performance or external component size. A synchronous output is available for controlling secondary side synchronous rectification to improve efficiency. User programmable protection features include monitors on input voltage (UVLO and OVLO) and switch current (overcurrent limit). A soft-start feature helps prevent transformer flux saturation.

The LT8310 main features include:

  • Input voltage range: 6 V to 100 V
  • Duty mode control regulates an isolated output without an opto
  • High efficiency synchronous control
  • Short-circuit (Hiccup mode) overcurrent protection
  • Programmable OVLO and UVLO with hysteresis
  • Programmable frequency (100 kHz to 500 kHz)
  • Synchronizable to an external clock
  • Positive or negative polarity output voltage feedback with a single FBX pin
  • Programmable soft-start
  • Shutdown current < 1 μA

The LT8310 is available in an FE20 TSSOP with high voltage pin spacing

Source: Elektor

High-Voltage LDO Regulator

To add to its growing family of voltage regulator solutions, Linear Technology recently announced the LT3061, a high-voltage, low-noise, low-dropout voltage linear regulator with active output discharge. The device can deliver up to 100 mA of continuous output current with a 250-mV dropout voltage at full load. The LT3061 features an NMOS pull-down that discharges the output when SHDN or IN is driven low. This rapid output discharge is useful for applications requiring power conditioning on both start-up and shutdown (e.g., high-end imaging sensors).

Source: Linear Technology

Source: Linear Technology

A single external capacitor provides programmable low noise reference performance and output soft-start functionality. The LT3061 has a quiescent current of 45 μA and provides fast transient response with a minimum 3.3-μF output capacitor. In shutdown, the quiescent current is less than 3 μA and the reference soft-start capacitor is reset.

Its main features include:

  • Wide 1.6 V to 45 V input voltage range.
  • Adjustable output voltages from 0.6 V to 19 V.
  • Ultralow noise operation of 30 µVRMS across a 10 Hz to 100 kHz bandwidth.
  • Low quiescent current of 45 µA (operating) and < 2 µA (in shutdown).

The LT3061 is available as an adjustable device with an output voltage range from the 600-mV reference up to 19 V. The chip is supplied in a thermally enhanced eight-lead 2 mm × 3 mm DFN and MSOP outline. For more information visit www.linear.com

 

 

 

New Dual Step-Down Regulator

Linear Technology recently announced an addition to its family of power regulator solutions. The LTC3622 is a dual step-down regulator in a small 3 × 4 mm package that provides two independently configurable 1-A outputs operating from a 2.7 to 17 V input. External voltage divider networks define the two output voltages or alternatively a range of fixed output voltage versions result in a lower component count. The input voltage range makes it suitable for operation from single or multiple lithium cells or from a vehicular supply.ltc3622-Linear

The regulator can operate in Burst mode to give highest efficiency at light loads or Pulse-Skipping mode to give lower ripple noise. The system clock can be synchronized to an external source to help to reduce system noise bandwidth.

Main Features:

  •  Dual step-down outputs: 1 A per channel
  •  VIN range: 2.7 to 17 V
  •  VOUT range: 0.6 V to VIN
  •  Up to 95% efficiency
  •  No-load IQ = 5 μA (both channels enabled)  < 4 μA (one channel enabled)
  •  High efficiency, low dropout operation (100% duty cycle)
  •  Constant frequency (1 MHz/2.25 MHz) with external synchronization
  •  ±1% output voltage accuracy
  •  Current mode operation improves line and load transient response
  •  Phase shift programmable with external clock
  •  Selectable current limit
  •  Internal compensation and soft-start
  •  Compact 14-pin DFN (3 mm × 4 mm) package

The regulator is available now with a per-unit cost starting at $3.75 for orders of 1,000 units.

[Source: Linear Technology]

Dual-Phase Boosts Step-Up Efficiency

Linear Technology Corp. recently introduced the LTC3124 two-phase, 3-MHz current-mode synchronous boost DC/DC converter. It features output disconnect and inrush current limiting. Dual-phase operation has the benefit of reducing peak inductor and capacitor ripple currents. This allows equivalent performance to be achieved in the power supply design with smaller valued inductors and capacitors.

Source: Linear Technology

Source: Linear Technology

The LTC3124 incorporates low resistance MOSFETs with an RDS(ON) of 130mΩ (N-channel) and 200mΩ (P-channel) to deliver efficiencies as high as 95%. The output disconnect feature allows the output to be completely discharged at shutdown and reduces switch-on inrush. An input pin can be used to configure the LTC3124 for continuous frequency mode to give low-noise operation. Additional features include external synchronization, output overvoltage protection, and robust short-circuit protection.

LTC3124’s main features:

  •  VIN Range: 1.8 V to 5.5 V, 500 mV after start-up
  •  Adjustable output voltage: 2.5 V to 15 V
  •  1.5-A Output current for VIN = 5 V and VOUT = 12 V
  •   Dual-phase control reduces output voltage ripple
  •  Output disconnects from input when shut down
  •  Synchronous rectification: up to 95% efficiency
  •  Inrush current limit
  •  Up to 3-MHz programmable switching frequency synchronizable to external clock
  •  Selectable Burst Mode operation: 25-µA IQ
  •  Output Overvoltage Protection
  •  Internal soft-start
  •  < 1 µA IQ in shutdown

The LTC3124EDHC and LTC3124EFE are both available from stock in 16-lead 3 mm x 5 mm DFN and thermally enhanced TSSOP packages, respectively. One-thousand-piece pricing starts at $3.26 each.

[via Elektor]

Battery Charger Design (EE Tip #130)

It’s easy to design a good, inexpensive charger. There is no justification for selling cheap, inadequate contraptions. Many companies (e.g., Linear Technology, Maxim, Semtech, and Texas Instruments) supply inexpensive battery management ICs. With a few external parts, you can build a perfect charger for just about any battery.

Texas Instruments’s UC2906 is an older (Unitrode) IC designed to build an excellent sealed lead-acid battery charger with a sophisticated charging profile. Figure 1 shows the recommended charger circuit.

Figure 1: This lead-acid battery charger uses Texas Instruments’s UC2906 IC.

Figure 1: This lead-acid battery charger uses Texas Instruments’s UC2906 IC.

In addition to the IC, only a handful of resistors and a PNP power transistor Q1 are needed to build it. Q1 must be rated for the maximum charging current and fitted with a heatsink.

An LED with its current-limiting resistor R can be connected to pin 7, which is an open-collector NPN transistor, to indicate the presence of power. Similarly, an LED with a series resistor could be connected to pin 9, which is also an open-collector NPN transistor to indicate overcharge (it is not used in Figure 1). The UC2906 datasheet and the Application Note provide tables and equations for selection of resistors Rs, Rt, RA, RB, RC, and RD and suggestions for adding various features.

Editor’s Note: This is an excerpt from an article written by George Novacek, “Battery Basics (Part 3): Battery Management ICs,” Circuit Cellar 280, 2013.