RE: IR receiver resistance

[Colin F. <tr...@ih...>]

Thanks,
=20
Are either of these suitable? I can't seem to find out what the actual
drop-out is for them.
=20
LD1117V50 +5V 800mA LDO Reg=20
Low Dropout Voltage Regulator
=20
(Thats all the info for that one)
=20
or this:

LM 2940T-5 +5V 1A LDO Regulatr=20
Low Dropout Voltage Regulator
*	LDO +5.0V
*	Positive Fixed LDO
*	Voltage, output:5V=20
*	Current output max:1A
*	Voltage input max:26V=20
*	Temperature operating (a) min:-40=B0C=20
*	Temperature operating (a) max:125=B0C=20
*	Pins number of:3=20
*	Case style:TO-220=20
*	Base number:2940=20
*	IC Generic number:2940=20

=09

________________________________

From: lir...@li...
[mailto:lir...@li...] On Behalf Of Peter Ma
Sent: Saturday, 7 January 2006 7:46 a.m.
To: Colin Findlay; lir...@li...
Subject: RE: IR receiver resistance


Hi, Colin...
=20
RS-232 drivers (your serial port) have pretty high output resistance.  =
The
IS1U621 looks to need 4.5mA; thus the sizeable voltage drop.  You need =
to
use a low drop-out (LDO) regulator.  Drop-out is the minimum allowable
difference between the input voltage and the output voltage for a =
regulator.
=20
One example of a sub-1V drop-out regulator is National Semi =
LP2980AIM5-5.0:
http://www.national.com/pf/LP/LP2980.html
=20
Regards,
Pete


________________________________

	From: lir...@li...
[mailto:lir...@li...] On Behalf Of Colin =
Findlay
	Sent: Thursday, January 05, 2006 3:53 PM
	To: lir...@li...
	Subject: IR receiver resistance
=09
=09
	Hi,
	=20
	I'm trying to put together a basic serial reciever, but I'm having
some voltage problems. The IR module (Sharp IS1U621) doesn't seem to be
getting enough voltage when connected.
	When it's not connected - I get 10.5V before the regulator - and 5V
after
	When the IR module is connected - I get 6.5V before the regulator -
and 4.3V after - This is not enough to power the module!
	I'm not really eletronics savy enough to work out why this is - and
what I need to do to fix it. Help?
	=20
	Regards
	Colin