SPX1117T Exar Corporation, SPX1117T Datasheet - Page 8

• Manufacturer Part Number: SPX1117T
• Description: 800mA Low Dropout Voltage Regulator
• Manufacturer: Exar Corporation

TABLE 1
Output Voltage
The output of the adjustable regulator can be set
to any voltage between 1.25V and 15V. The
value of V
the formula
A small correction to this formula is required
depending on the values of resistors R
since the adjustable pin current (approx 50µA)
flows through R
count, the formula becomes
Date: 8/25/04
Figure 21. Current Source
V
IN
PC BOARD
2500
2500
2500
2500
2500
1600
2500
2500
1600
4.7µF
900
900
mm
+
I
OUT
OUT
2
C
V
1
=
OUT
can be quickly approximated using
V
IN
R
REF
1
=1.25 *(R
2
. When I
SPX1117
TOPSIDE COPPER
ADJ
1
2500
1250
2500
1800
1250
mm
+ R
ADJ
950
600
915
600
240
240
OUT
SPX1117 800mA Low Dropout Voltage Regulator
2
is taken into ac-
2
)/R
LOAD
1
.
R
1
1
I
OUT
and R
C
BACKSIDE COPPER
2
V
OUT
2
,
2500
2500
2500
1600
900
8
mm
APPLICATION INFORMATION: Continued
0
0
0
0
0
0
2
where
Layout Considerations
lation. In order to avoid this, connect R
to V
reason, R
side of the load.
Parasitic line resistance can degrade load regu-
Figure 22. Typical Adjustable Regulator
OUT
V
IN
V
4.7µF +
V
OUT
as illustrated in Figure 25. For the same
OUT
2
= V
= V
should be connected to the negative
REF
C
1
(1+R
REF
IN
THERMAL RESISTANCE
2
V
/R
(1+ (R
1
) +I
REF
SPX1117
JUNC. TO AMB.
ADJ
=1.25V.
R
© Copyright 2004 Sipex Corporation
ADJ
50µA
I
ADJ
2
2
/R
°C/W
1
OUT
)) + I
46
47
49
51
53
55
58
59
67
72
85
V
REF
ADJ
R
R
1
2
* R
C
1
2
directly
2
V
,
OUT