LTC1044AIN8 Linear Technology, LTC1044AIN8 Datasheet - Page 7

• Manufacturer Part Number: LTC1044AIN8
• Description: IC CMOS VOLT CONV SW-CAP 8-DIP
• Manufacturer: Linear Technology
• Type: Step-Up (Boost), Switched Capacitor (Charge Pump), Divider, Doubler, Invertingr

Specifications of LTC1044AIN8

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Current - Output: 20mA
• Frequency - Switching: 1kHz ~ 5kHz
• Voltage - Input: 1.5 ~ 12 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Output: -
• Power - Output: -

A
Capacitor Selection
External capacitors C1 and C2 are not critical. Matching
is not required, nor do they have to be high quality or
tight tolerance. Aluminum or tantalum electrolytics are
excellent choices with cost and size being the only
consideration.
Negative Voltage Converter
Figure 6 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 LV
pin (pin 6) is shown grounded, but for V
“floated”, since LV is internally switched to ground (pin 3)
for V
The output voltage (pin 5) characteristics of the circuit are
those of a nearly ideal voltage source in series with an 80
resistor. The 80 output impedance is composed of two
terms:
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.
PPLICATI
R
=
1. The equivalent switched-capacitor resistance (see
2. A term related to the on-resistance of the MOS
EQUIV
5
+
Theory of Operation).
switches.
T
MIN
+
3V.
10
10 F
=
T
3
A
Figure 6. Negative Voltage Converter
(f
T
OSC
MAX
1
1
2
3
4
10
O
/2)
LTC1044A
1
U
10
LTC1044A • F06
S
–6
C1
I FOR ATIO
C
U
= 20
= 1/ C) and does not contain
8
7
6
5
+
10 F
V
+
REQUIRED FOR V
EQUIV
(1.5V TO 12V)
W
+
V
is not a capaci-
OUT
3V it may be
= – V
+
U
< 3V
+
The exact expression for output resistance is extremely
complex, but the dominant effect of the capacitor is clearly
shown on the typical curves of Output Resistance and
Power Efficiency vs Frequency. For C1 = C2 = 10 F, the
output impedance goes from 60 at f
at f
compared to the switch-on resistance term, the output
resistance is determined by 1/(f C) only.
Voltage Doubling
Figure 7 shows a two-diode capacitive voltage doubler.
With a 5V input, the output is 9.93V with no load and 9.13V
with a 10mA load. With a 10V input, the output is 19.93V
with no load and 19.28V with a 10mA load.
Ultra-Precision Voltage Divider
An ultra-precision voltage divider is shown in Figure 8. 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.
OSC
1
2
3
4
V
T
I
L
MIN
+
/2 ±0.002%
100nA
= 1kHz. As the 1/(f
LTC1044A
T
Figure 8. Ultra-Precision Voltage Divider
A
LTC1044A • F07
+
T
MAX
Figure 7. Voltage Doubler
C1
10 F
8
7
6
5
+
REQUIRED
FOR V
1
2
3
4
C2
10 F
+
LTC1044A
1N5817
< 3V
REQUIRED FOR
(1.5V TO 12V)
LTC1044A • F08
V
V
d
+
+
< 6V
V
C) term becomes large
IN
+
10 F
+
8
7
6
5
1N5817
OSC
V
d
LTC1044A
= 10kHz to 200
+
V
+
(3V TO 24V)
10 F
V
OUT
= 2(V
IN
7
– 1)