LTC1044ACN8 Linear Technology, LTC1044ACN8 Datasheet - Page 6

• Manufacturer Part Number: LTC1044ACN8
• 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 LTC1044ACN8

• 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: 0°C ~ 70°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: -

LTC1044A
A
LV (Pin 6)
The internal logic of the LTC1044A runs between V
LV (pin 6). For V
switch shorts LV to GND (pin 3). For V
LV pin should be tied to GND. For V
to 3V, the LV pin can be tied to GND or left floating.
OSC (Pin 7) and Boost (Pin 1)
The switching frequency can be raised, lowered, or driven
from an external source. Figure 4 shows a functional
diagram of the oscillator circuit.
By connecting the boost pin (pin 1) to V
discharge current is increased and hence, the frequency is
increased by approximately 7 times. Increasing the
6
PPLICATI
BOOST
(1)
LV
(6)
O
+
greater than or equal to 3V, an internal
6I
6I
U
Figure 4. Oscillator
S
V
+
BOOST
I FOR ATIO
OSC
I
I
Figure 3. LTC1044A Switched-Capacitor Voltage Converter Block Diagram
U
7X
(1)
(7)
LTC1044A • F04
~14pF
+
OSC
W
greater than or equal
LV
(6)
+
OSC
(7)
+
less than 3V, the
, the charge and
SCHMITT
TRIGGER
(8)
V
CLOSED WHEN
+
2
U
V
+
+
> 3V
and
SW1
frequency will decrease output impedance and ripple for
higher load currents.
Loading pin 7 with more capacitance will lower the fre-
quency. Using the boost (pin 1) in conjunction with exter-
nal capacitance on pin 7 allows user selection of the
frequency over a wide range.
Driving the LTC1044A from an external frequency source
can be easily achieved by driving pin 7 and leaving the
boost pin open as shown in Figure 5. The output current
from pin 7 is small (typically 0.5 A) so a logic gate is
capable of driving this current. The choice of using a
CMOS logic gate is best because it can operate over a wide
supply voltage range (3V to 15V) and has enough voltage
swing to drive the internal Schmitt trigger shown in Figure
4. For 5V applications, a TTL logic gate can be used by
simply adding an external pull-up resistor (see Figure 5).
GND
(2)
(4)
(3)
C
C
+
+
–
+
C1
NC
C1
1
2
3
4
LTC1044A
SW2
Figure 5. External Clocking
LTC1044A • F03
8
7
6
5
V
(5)
OUT
+
+
100k
REQUIRED FOR
TTL LOGIC
C2
C2
LTC1044A • F05
–(V
+
)
V
+
OSC INPUT