Datasheet
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SBOS301A − MAY 2004 − REVISED MARCH 2007
www.ti.com
19
DATA COMPRESSION
In many applications, the compressive effects of the
logarithmic transfer function are useful. For example, a
LOG114 preceding a 12-bit ADC can produce the
dynamic range equivalent to a 20-bit converter. (Sug-
gested products: ADS7818, ADS7834).
+3.3V OPERATION
For systems with only a +3.3V power supply, the
TPS60241 zero-ripple switched cap buck-boost 2.7V to
5.5V input to 5V output converter may be used to gener-
ate a +5V supply for the LOG114, as shown in
Figure 11.
Likewise, the TPS6040 negative charge pump may be
connected to the +5V output of the TPS60241 to gener-
ate a −5V supply to create a ±5V supply for the
LOG114, as Figure 12 illustrates.
+5V
LOG114
I
1
I
2
V
LOGOUT
TPS60241
C
2+
C
2
−
C
1+
V
IN
C
1
−
V
OUT
ENGND
+3.3V
C
0
1
µ
F
C
2
1
µ
F
C
1
1
µ
F
C
1
1µF
V
−
V+
Figure 11. Creating a +5V Supply from a +3.3V Supply.
+5V
LOG114
I
1
I
2
C
FLY
1
µ
F
C
O
1
µ
F
C
I
1
µ
F
C
O
1
µ
F
C
2
1
µ
F
V
IN
C
1+
C
1
−
V
OUT
C
2+
C
2
−
C
1
1
µ
F
C
1
1
µ
F
C
FLY−
C
FLY+
−
5V
V
LOGOUT
TPS60241
ENGND
+3.3V
V+
+5V
V
−
−
5V
TPS60400
IN
OUT
GND
Figure 12. Creating a ±5V Supply from a +3.3V Supply.