LM7806 Problem

[west]

Data sheets re LM7806 advise that the input voltage should not exceed the
output by more than 2 to 3V. My input voltage is a deep cycle 12V battery
while my output requirement is 6V. What can I do to not overheat the
regulator. Is there a better way to get 6V from a 12V wheel chair battery?
The 6V is for a small handi talkie radio. Thank you in advance.

west

 

[Ernie Werbel]

Data sheets re LM7806 advise that the input voltage should not exceed the
output by more than 2 to 3V. My input voltage is a deep cycle 12V battery
while my output requirement is 6V. What can I do to not overheat the
regulator.

If the input cannot exceed the output by 2-3V, then don't put more than 8-9
volts into it. I suppose you could put a LM7809 (9V reg.) in between the
12V and the '7806 to ''step it down'' from 12.

Is there a better way to get 6V from a 12V wheel chair battery?
The 6V is for a small handi talkie radio. Thank you in advance.

I would think that four dry cells would be sufficient for a handheld radio.
Or, you could try size "J", a flat, rectangular 6-volt battery.

 

[Ryan Weihl]

west wrote:

Data sheets re LM7806 advise that the input voltage should not exceed
the output by more than 2 to 3V. My input voltage is a deep cycle 12V
battery while my output requirement is 6V. What can I do to not
overheat the regulator. Is there a better way to get 6V from a 12V
wheel chair battery? The 6V is for a small handi talkie radio. Thank
you in advance.

west

the fairchild data sheet says max. input voltage is 35V (page 2)
http://www.fairchildsemi.com/ds/LM/LM7812.pdf

rw

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[JeffM]

Data sheets re LM7806 advise that
the input voltage should not exceed the output by more than 2 to 3V.
west

You read it wrong. This is called Dropout Voltage.
Input voltage MUST always exceed the output voltage by AT LEAST 2V.
That is, it is *not* an LDO (Low Dropout regulator).

 

[Geoff]

west wrote:

Data sheets re LM7806 advise that the input voltage should not exceed
the output by more than 2 to 3V. My input voltage is a deep cycle 12V
battery while my output requirement is 6V. What can I do to not
overheat the regulator. Is there a better way to get 6V from a 12V
wheel chair battery? The 6V is for a small handi talkie radio. Thank
you in advance.

No, they say the input voltage MUST exceed the output by the 2 or 3 volts.

geoff

 

[jasen]

On 2006-07-23, west <restccq2@verizon.net> wrote:

Data sheets re LM7806 advise that the input voltage should not exceed the
output by more than 2 to 3V.

look again.

Bye.
Jasen