RE: IR receiver resistance

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

Size is not an issue - but these are really the only 2 readily available =
in
New Zealand via Dick Smiths. (www.dse.co.nz)
The standard lirc circuit already includes a 4.7uF capacitor, I assume =
this
would be fine fine to replace with something like a 22uF?=20

-----Original Message-----
From: Peter Ma [mailto:Pe...@ze...]=20
Sent: Saturday, 7 January 2006 2:37 p.m.
To: Colin Findlay; lir...@li...
Subject: RE: IR receiver resistance

Yes, both should work okay; but they are overkill.  But note that many =
LDO
regulators do have output capacitor requirements to maintain stability.
These two require values that are quite high (10 to 22uF minimum), =
whereas
the LP2980 needs min. 1uF.  Judging from the packages you are looking =
at, I
am guessing size is not a concern for you.

Regards,
Pete

> -----Original Message-----
> From: Colin Findlay [mailto:tr...@ih...]
> Sent: Friday, January 06, 2006 5:15 PM
> To: Peter Ma; lir...@li...
> Subject: RE: IR receiver resistance
>=20
> 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
> Low Dropout Voltage Regulator
> =20
> (Thats all the info for that one)
> =20
> or this:
>=20
> LM 2940T-5 +5V 1A LDO Regulatr
> 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
>=20
> =09
>=20
> ________________________________
>=20
> 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
>=20
>=20
> 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. =20
> You need to use a low drop-out (LDO) regulator.  Drop-out is the=20
> minimum allowable difference between the input voltage and the output=20
> 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