LTC1144CS8 Linear Technology, LTC1144CS8 Datasheet - Page 7

• Manufacturer Part Number: LTC1144CS8
• Description: IC VOLT CONV SW-CAP W/SHTDN8SOIC
• Manufacturer: Linear Technology
• Type: Switched Capacitor (Charge Pump), Invertingr

Specifications of LTC1144CS8

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Current - Output: 50mA
• Frequency - Switching: 4kHz ~ 10kHz
• Voltage - Input: 2 ~ 18 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Power - Output: 500mW
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Output: -

At an oscillator frequency of 10kHz and C1 = 10 F, the first
term is:
Notice that the above equation for R
tive reactance equation (X
a 2 term.
The exact expression for output impedance is extremely
complex, but the dominant effect of the capacitor is clearly
shown in Figure 5. For C1 = C2 = 10 F, the output
impedance goes from 56 at f
f
to the switch on-resistance term, the output resistance is
determined by 1/(f C) only.
Voltage Doubling
Figure 9 shows a two-diode capacitive voltage doubler.
With a 15V input, the output is 29.45V with no load and
28.18V with a 10mA load.
TYPICAL
Negative Voltage Converter
Figure 8 shows a typical connection which will provide a
negative supply from an available positive supply. This
circuit operates over full temperature and power supply
ranges without the need of any external diodes.
The output voltage (pin 5) characteristics of the circuit are
those of a nearly ideal voltage source in series with a 56
resistor. The 56 output impedance is composed of two
terms: 1) the equivalent switched capacitor resistance
(see Theory of Operation), and 2) a term related to the on-
resistance of the MOS switches.
R
OSC
EQUIV
= 1kHz. As the 1/(f C) term becomes large compared
10 F
f
+
OSC
Figure 8. Negative Voltage Converter
A
1
2
PPLICATI
1
2
3
4
T
MIN
C
LTC1144
1
T
A
C
5 10
T
= 1/ C) and does not contain
MAX
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
O
2V TO 18V
8
7
6
5
OSC
3
V
U
+
+
EQUIV
1
10 10
= 10kHz to 250 at
10 F
S
is not a capaci-
V
OUT
6
= –V
1144 F08
+
20
Ultra-Precision Voltage Divider
An ultra-precision voltage divider is shown in Figure 10. To
achieve the 0.0002% accuracy indicated, the load current
should be kept below 100nA. However, with a slight loss
in accuracy, the load current can be increased.
Battery Splitter
A common need in many systems is to obtain (+) and (–)
supplies from a single battery or single power supply
system. Where current requirements are small, the circuit
shown in Figure 11 is a simple solution. It provides
symmetrical output voltages, both equal to one half the
input voltage. The output voltages are both referenced to
pin 3 (output common).
18V
V
B
+
T
MIN
1
2
3
4
10 F
V+
Figure 10. Ultra-Precision Voltage Divider
C1
2
I
T
L
LTC1144
±0.002%
A
100nA
10 F
+
T
MAX
C1
Figure 9. Voltage Doubler
Figure 11. Battery Splitter
+
1
2
3
4
8
7
6
5
+
LTC1144
1N4148
1
2
3
4
C2
10 F
V
2V TO 18V
d
+
LTC1144
V
IN
+
8
7
6
5
+
10 F
1N4148
V
d
+
C2
10 F
4V TO 36V
8
7
6
5
+
V
LTC1144
+
10 F
V
9V
–V
–9V
OUTPUT
COMMON
V
1144 F10
B
OUT
/2
B
/2
1144 F11
= 2(V
IN
1144 F09
– 1)
7