LTC1046 Linear Technology, LTC1046 Datasheet - Page 4

• Manufacturer Part Number: LTC1046
• Description: Inductorless 5V to + 5V Converter
• Manufacturer: Linear Technology

LTC1046
TYPICAL PERFOR
TEST CIRCUIT
A
Theory of Operation
To understand the theory of operation of the LTC1046, a
review of a basic switched capacitor building block is
helpful.
In Figure 2, when the switch is in the left position, capacitor
C1 will charge to voltage V1. The total charge on C1 will be
q1 = C1V1. The switch then moves to the right, discharg-
ing C1 to voltage V2. After this discharge time, the charge
on C1 is q2 = C1V2. Note that charge has been transferred
from the source, V1, to the output, V2. The amount of
charge transferred is:
4
PPLICATI
q = q1 – q2 = C1(V1 – V2).
100
10
1
0
Oscillator Frequency as a
Function of Supply Voltage
T
C
A
OSC
= 25 C
O
1
= 0pF
AMBIENT TEMPERATURE ( C)
U
2
S
3
I FOR ATIO
U
W
10 F
4
C1
A
+
U
5
CE
W
6
1046 G10
1
2
3
4
C
BOOST
CAP
GND
CAP
HARA TERISTICS
7
LTC1046
+
–
V
U
OSC
OUT
V
LV
+
C
8
7
6
5
Figure 1
C
If the switch is cycled “f” times per second, the charge
transfer per unit time (i.e., current) is:
OSC
I = f • q = f • C1(V1 – V2).
EXTERNAL
OSCILLATOR
Figure 2. Switched Capacitor Building Block
40
38
36
34
32
30
28
26
(Using Test Circuit in Figure 1)
–55
Oscillator Frequency vs
Temperature
V1
–25
R
V
L
+
AMBIENT TEMPERATURE ( C)
(5V)
+
1046 F01
0
I
I
C2
10 F
L
S
C1
V
f
25
OUT
50
C2
75
V
C
+
OSC
R
1046 F02
L
= 5V
100
= 0pF
1046 G11
V2
125