Specifications

27
Figure 2.3.7-1: TL780-05 Fixed-output voltage regulator implementation
diagram. Reproduced with permission from Texas Instruments.
2.3.8 Voltage Regulator Comparison
Each discussed circuit has its own advantages and disadvantages. The specifics
of these properties were discussed in each section. Given the requirements of
the voltage regulator, the LM1117 and TL780-05 is the best fit. It has a good
temperature range, small size, simplicity in implementation, and can accept a
relatively wide range of voltage input while outputting a constant 3.3Vdc or 5Vdc,
which should be sufficient for the other components on the boards. Both units will
have voltage regulators on their respective boards.
The portable unit will use a voltage regulator to ensure voltage coming from the
fixed unit is indeed regulated and acceptable for the battery. The portable unit will
use a voltage regulator to ensure stable power to its own circuit. A tabular
summary of the overall comparison is available in Table 2.2.8-1.
Regulation
Solution
Input
Voltage
Output
Voltage
Compact?
Less than
$3?
Lead
Times
Zener Diode
Variable
Fixed to diode
spec
Yes
Yes
<1 Week
Voltage Divider
Variable
Variable
Yes
Yes
<1 Week
Regulator
Board
Variable
Fixed to 12V
and 5V
No
No
2-3 Weeks
LM 317
Variable
Adjustable to
5V
Yes
Yes
1-2 Weeks
LM1117#33
Variable
3.3V Fixed
Yes
Yes
1-2 Weeks
TL780-05
Variable
5V Fixed
Yes
Yes
1-2 Weeks
Table 2.3.8-1: Comparison of voltage regulators