5v supply

[shahidali55]

How can i build a high efficiency 5 volt supply for micro controllers...
The LM7805 uses nearly 6mA for itself...
Is there any way i can build a 5v regulator which uses less than 100uA for itself?

[psdayama]

How can i build a high efficiency 5 volt supply for micro controllers...
The LM7805 uses nearly 6mA for itself...
Is there any way i can build a 5v regulator which uses less than 100uA for itself?

The 6mA current is not much problem but input output differential of minimum
2.5Volts puts a big premium on efficiency. Most circuits have input of 9-10V for output of 5v. As such there is hardly 30-40% effficiency in series regulator
like LM7805.
For better efficiency one should use switching regulators to get 5V with
acceptable ripple and regulation for microcontrollers. Otherway is to use
LM2825-5V which has builtin everything and delivers 1Ampere just like 7805.
Cost is then no consideration.

[Luciano]

Hi,

LP2950

- 75 μA quiescent current
- 100 mA output current

http://cache.national.com/ds/LP/LP2950.pdf

Best regards,

Luciano


The LP2950 and LP2951 are micropower voltage regulators
with very low quiescent current (75 μA typ.) and very low
dropout voltage (typ. 40 mV at light loads and 380 mV at
100 mA). They are ideally suited for use in battery-powered
systems. Furthermore, the quiescent current of the LP2950/
LP2951 increases only slightly in dropout, prolonging battery
life.


The LP2950-5.0 is available in the surface-mount D-Pak
package, and in the popular 3-pin TO-92 package for
pin-compatibility with older 5V regulators. The 8-lead
LP2951 is available in plastic, ceramic dual-in-line, or metal
can packages and offers additional system functions.
One such feature is an error flag output which warns of a low
output voltage, often due to falling batteries on the input. It
may be used for a power-on reset. A second feature is the
logic-compatible shutdown input which enables the regulator
to be switched on and off. Also, the part may be pin-strapped
for a 5V, 3V, or 3.3V output (depending on the version), or
programmed from 1.24V to 29V with an external pair of resistors.
Careful design of the LP2950/LP2951 has minimized all contributions
to the error budget. This includes a tight initial tolerance
(.5% typ.), extremely good load and line regulation
(.05% typ.) and a very low output voltage temperature coefficient,
making the part useful as a low-power voltage reference.

Features
- 5V, 3V, and 3.3V versions available
- High accuracy output voltage
- Guaranteed 100 mA output current
- Extremely low quiescent current
- Low dropout voltage
- Extremely tight load and line regulation
- Very low temperature coefficient
- Use as Regulator or Reference
- Needs minimum capacitance for stability
- Current and Thermal Limiting
- Stable with low-ESR output capacitors


LP2951 versions only

- Error flag warns of output dropout
- Logic-controlled electronic shutdown
- Output programmable from 1.24 to 29V