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'[EE] Switch Mode Current regulation'
2003\06\04@102338 by Timothy Box

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Hi

As part of a battery charging circuit I need to regulate the current. The
problem is I cannot lose the heat in the hand held device so need to use a
Switch mode Current regulator. I have found them to be very thin on the
ground. Can anybody recommend one?  It needs to be capable of about 1500ma
at 5V (I am charging 4 AA NIMH batteries)


Many thanks


Tim

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2003\06\04@103733 by Bob Axtell

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I had incredible luck with National's 50Khz series , LM2576 in D2T mode. It
never gets warmer than 30C, and is 95% efficient, even operates down to
bottom+1V! NO heat. A wonderful part. Be careful to use the inductor they
recommend, to prevent flux saturation.

It will still be working into the next century.

--Bob

At 03:24 PM 6/4/2003 +0100, you wrote:
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2003\06\04@110338 by Eduardo Garcia

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Hello Timothy,
   Try MIC4576.
   It is a 3A switched buck regulator that may work cold at 1,5A.
   There are other switched regulators that need external transistors and
other components so MIC4576 use a simplest circuit as well.

Sorry my bad english but I hope you understood me.


{Original Message removed}

2003\06\04@112317 by Harold Hallikainen

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    You're probably looking for a buck converter, but I thought I'd point out a couple boost converters I looked at recently. The LT1618 is interesting in that it has a pair of high side inputs for measuring across a current sense resistor so you can do constant current regulation. It needs 50mV across the sense resistor.
    Unfortunately, the LT1618 could not output enough power for the application I had (dumping 10W, 7V at 1.5A into an LED), so I ended up using the LT1370. This does not have a current sense input. It needs something like 1.25V on the feedback input. I put a 40 milliohm current sense resistor in series with the load and amplified the sense voltage by 20 with a MAX4073TAUT-T sense amplifier. This drives the feedback input of the LT1370. Works well. About 5,000 units built so far...
    Finally, it'd be great if you could find a chip specifically designed for charging the batteries you're charging. In my application, we're using a pair of 2AH lithium ion cells in parallel. The LTC1733 linear charger does a great job. It handles dead battery conditioning, constant current charge, constant voltage charge, and time-out. You set the constant current with a resistor to ground on one pin. You can measure the voltage on that pin to determine the output current (I detect end of charge current watching that voltage with a PIC). Raising that pin voltage to 5V shuts down the charger. Nice chip!

Harold

Harold

--- Eduardo Garcia <.....egnascimentoKILLspamspam.....YAHOO.COM.BR> wrote:

Hello Timothy,
   Try MIC4576.
   It is a 3A switched buck regulator that may work cold at 1,5A.
   There are other switched regulators that need external transistors and
other components so MIC4576 use a simplest circuit as well.

Sorry my bad english but I hope you understood me.


{Original Message removed}

2003\06\04@113337 by Eduardo Garcia

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Yes, LM2576 is also a good choice.

Good Luck!

----- Original Message -----
From: "Bob Axtell" <EraseMEcr_axtellspam_OUTspamTakeThisOuTYAHOO.COM>
To: <PICLISTspamspam_OUTMITVMA.MIT.EDU>
Sent: Wednesday, June 04, 2003 11:36 AM
Subject: Re: [EE] Switch Mode Current regulation


> I had incredible luck with National's 50Khz series , LM2576 in D2T mode.
It
{Quote hidden}

1500ma
{Quote hidden}

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