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

Low-Drop Series Regulator Using a TL431 (EE Tip #134)

You likely have a stash of 12-V lead acid batteries (such as the sealed gel cell type) in your lab or circuit cellar. Below is a handy tip from Germany-based Lars Krüger for a simple way to charge them.

A simple way of charging them is to hook up a small unregulated 15-V wall wart power supply. This can easily lead to overcharging, though, because the off-load voltage is really too high. The remedy is a small but precise series regulator using just six components, which is connected directly between the power pack and the battery (see schematic) and doesn’t need any heatsink.EL2009-Kruger-SeriesReg

The circuit is adequatele proof against short circuits (minimum 10 seconds), with a voltage drop of typically no more than 1 V across the collector-emitter path of the transistor.

For the voltage source you can use any transformer power supply from around 12 V to 15 V delivering a maximum of 0.5 A. By providing a heatsink for T1 and reducing the value of R1 you can also redesign the circuit for higher currents.

Resource: http://focus.ti.com/lit/ds/symlink/tl431.pdf. This tip first appeared in Elektor July/August 2009.

Configurable Regulator

LinearThe LTM4644 quad output step-down µModule (micromodule) regulator is configurable as a single (16-A), dual (12-A, 4-A, or 8-A, 8-A), triple (8-A, 4-A, 4-A), or quad (4-A each) output regulator. This flexibility enables system designers to rely on one simple and compact µModule regulator for the various voltage and load current requirements of FPGAs, ASICs, and microprocessors as well as other board circuitry. The LTM4644 is ideal for communications, data storage, industrial, transportation, and medical system applications.

The LTM4644 regulator includes DC/DC controllers, power switches, inductors and compensation components. Only eight external ceramic capacitors (1206 or smaller case sizes) and four feedback resistors (0603 case size) are required to regulate four independently adjustable outputs from 0.6 to 5.5 V. Separate input pins enable the four channels to be powered from a common supply rail or different rails from 4 to 14 V.

At an ambient temperature of 55°C, the LTM4644 delivers up to 13 A at 1.5 V from a 12-V input or up to 14 A with 200-LFM airflow. The four channels operate at 90° out-of-phase to minimize input ripple whether at the 1-MHz default switching frequency or synchronized to an external clock between 700 kHz and 1.3 MHz. With the addition of an external bias supply above 4 V, the LTM4644 can regulate from an input supply voltage as low as 2.375 V. The regulator also includes output overvoltage and overcurrent fault protection.

The LTM4644 costs $22.85 each in 1,000-unit quantities.

Linear Technology Corp.
www.linear.com

High-Voltage Gate Driver IC

Allegro A4900 Gate Driver IC

Allegro A4900 Gate Driver IC

The A4900 is a high-voltage brushless DC (BLDC) MOSFET gate driver IC. It is designed for high-voltage motor control for hybrid, electric vehicle, and 48-V automotive battery systems (e.g., electronic power steering, A/C compressors, fans, pumps, and blowers).

The A4900’s six gate drives can drive a range of N-channel insulated-gate bipolar transistors (IGBTs) or power MOSFET switches. The gate drives are configured as three high-voltage high-side drives and three low-side drives. The high-side drives are isolated up to 600 V to enable operation with high-bridge (motor) supply voltages. The high-side drives use a bootstrap capacitor to provide the supply gate drive voltage required for N-channel FETs. A TTL logic-level input compatible with 3.3- or 5-V logic systems can be used to control each FET.

A single-supply input provides the gate drive supply and the bootstrap capacitor charge source. An internal regulator from the single supply provides the logic circuit’s lower internal voltage. The A4900’s internal monitors ensure that the high- and low-side external FET’s gate source voltage is above 9 V when active.

The control inputs to the A4900 offer a flexible solution for many motor control applications. Each driver can be driven with an independent PWM signal, which enables implementation of all motor excitation methods including trapezoidal and sinusoidal drive. The IC’s integrated diagnostics detect undervoltage, overtemperature, and power bridge faults that can be configured to protect the power switches under most short-circuit conditions. Detailed diagnostics are available as a serial data word.

The A4900 is supplied in a 44-lead QSOP package and costs $3.23 in 1,000-unit quantities.

Allegro MicroSystems, LLC
www.allegromicro.com