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Saturday, May 16, 2015

Power Supply Regulators and MOSFET Transistor

HELLO THERE ...COULD anybody pls help me with a place to get more information on the following components...cant seem to find it anywhere.

W20NB50 W8NB100 found them in a liteon power supply pack for a database supply. i just don't know what they stand for. ...saw on a web page that it is produced by ST micro electronics. i went there but no show ..can somebody pls help?

post by FP

W20NB50 ST Power MOSFET Transistors TO-247 N-Ch 500 Volt 20 Amp
W8NB100 ST Power MOSFET Transistors TO-247 N-Ch 1000 Volt 8 Amp

You  will find equivalents here - NTE Electronics - N-Channel MOSFET Selector

ST’s MOSFETs with a breakdown voltage > 650 V offer low gate charge and low on-resistance down to 0.275 Ω (850 V) in PowerFLAT 8x8 HV packages.

Junction design of a Mosfet

Junction design of a Mosfet

"The source-to-body and drain-to-body junctions are the object of much attention because of three major factors: their design affects the current-voltage (I-V) characteristics of the device, lowering output resistance, and also the speed of the device through the loading effect of the junction capacitances, and finally, the component of stand-by power dissipation due to junction leakage."

Updated - July 2013


Thursday, May 14, 2015

uC Board is Buggy on Brown Out

I'm working on a project which involves battery  Ni-Mh 4x1.2v, 2100mAh], which power-ups the boards. The current consumption is about 150mA. Now what I wish to do is disconect the load when my battery voltage falls down to 4v or so

Because now when my battery reaches this voltage the instrument fails to work, sometimes my program gets corrupted. And battery reaches a critical voltage level like 1-1.2(summation of all 4 batt). what else can I do so prevent this?

Mail from MO

Depending on your budget you can solve this, a watchdog and power management chip from maxim may work for these types of problems.

You can even build your own watchdog and power management with logic and comparators.

When the uP malfunctions it has to be reset by a watchdog timer which monitors if the uP or uC is pulsing in the way expected.

Battery Backup for SRAM or Microcontroller

And when the power goes down slowly like a Brown out, you have to save all RAM on a Flash chip and shutdown system and wait. Or have another backup for RAM and use a low power RAM. Make sure that you write a start sequence and shutdown code in your program.

When you start start with a clear ram ( if not batt backed up) then load values from flash. Make sure power up, power down resets are ok.

Digital to Analog Converter with uC Watchdog

Internal comparators implement undervoltage/overvoltage warnings and windowed-reset functions.

Supervisory Circuits Keep Your Microprocessor Under Control


Supervisory Circuits Keep Your Microprocessor Under Control

"Understand the value of a µP supervisor to ensure proper system operation during power-up, power-down, and brownout situations (undervoltage monitoring). In addition, provides information about overvoltage and windowed monitoring. Describes additional features such as manual reset, watchdog timer, battery backup, and chip enable gating. Discusses the need for multi-voltage monitoring."

In an industrial environment your card it may malfunction due to EMI RFI. If your Board controls a huge Motor, when motor starts your Board could hang or Boot. You have to study and work out a solution.

The circuit or code is not everything, it is the Engineering that matters.