sg117aig/desc Microsemi Corporation, sg117aig/desc Datasheet - Page 7

• Manufacturer Part Number: sg117aig/desc
• Description: 1.5 Amp Three Terminal Adjustable Voltage Regulator
• Manufacturer: Microsemi Corporation

Copyright © 1994
Rev. 1.3, 2006-02-08
G
between the output and the adjustable terminal (see Figure
1). By placing a resistor, R
constant current is caused to flow through R
through R
current is the specified minimum load current of 5mA or
10mA.
with the current through R
can usually be ignored.
resistors were of exact value, the accuracy of the output is
limited by the accuracy of V
regulators had a reference tolerance of ±4%. This tolerance
is dangerously close to the ±5% supply tolerance required
in many logic and analog systems. Further, many 1%
resistors can drift 0.01%°C adding another 1% to the output
voltage tolerance.
VREF, calculations will show that the expected range of a
5V regulator design would be 4.66V < V
approximately ±7%. If the same example were used for a
15V regulator, the expected tolerance would be ±8%. With
these results most applications require some method of
trimming, usually a trim pot. This solution is expensive and
not conducive to volume production.
regulators over existing devices is tightened initial
tolerance. This allows relatively inexpensive 1% or 2% film
resistors to be used for R
voltage within an acceptable tolerance range.
design, using ±2% resistors, would have a worse case
manufacturing tolerance of ±4%. If 1% resistors were used,
the tolerance would drop to ±2.5%. A plot of the worst case
output voltage tolerance as a function of resistor tolerance
is shown on the front page.
ENERAL
The SG117A develops a 1.25V reference voltage
Because I
It is easily seen from the above equation, that even if the
For example, using 2% resistors and ±4% tolerance for
One of the enhancements of Silicon General’s adjustable
With a guaranteed 1% reference, a 5V power supply
TM
2
to set the overall output voltage, Normally this
ADJ
Figure 17 – Basic Regulator Circuit
V
is very small and constant when compared
OUT
=
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
V
REF
⎛
⎜ ⎜
⎝
1
1
1
, it represents a small error and
1
between these two terminals, a
R
R
and R
2
1
⎞
⎟ ⎟
⎠
+
REF
I
2
ADJ
. Earlier adjustable
A P P L I C A T I O N I N F O R M A T I O N
while setting output
•
R
2
OUT
Integrated Products Division
1
< 5.36V or
and down
®
Microsemi
1.5A Three Terminal Adj. Voltage Regulator
SG117 / 217 / 317 / 117A / 217A / 317A
is shown below
Decade Table by multiplying by multiples of 10. As an
example: 1.21 can represent 1.21Ω, 12.1Ω, 121Ω, 1.21kΩ,
etc.
For convenience, a table of standard 1% resistor values
Standard Resistance Values are obtained from the
Figure 18 – Connections for Best Load Regulation
Table of ½% and 1% Standard Resistance Values
1.00
1.02
1.05
1.07
1.10
1.13
1.15
1.18
1.21
1.24
1.27
1.30
1.33
1.37
1.40
1.43
Figure 19 – 1.2V – 25V Adjustable Regulator
1.47
1.50
1.54
1.58
1.62
1.65
1.69
1.74
1.78
1.82
1.87
1.91
1.96
2.00
2.05
2.10
2.15
2.21
2.26
2.32
2.37
2.43
2.49
2.55
2.61
2.67
2.74
2.80
2.87
2.94
3.01
3.09
3.16
3.24
3.32
3.40
3.48
3.57
3.65
3.74
3.83
3.92
4.02
4.12
4.22
4.32
4.42
4.53
4.64
4.75
4.87
4.99
5.11
5.23
5.36
5.49
5.62
5.76
5.90
6.04
6.19
6.34
6.49
6.65
6.81
6.98
7.15
7.32
7.50
7.68
7.87
8.06
8.25
8.45
8.66
8.87
9.09
9.31
9.53
9.76
Page 7