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.