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PDF LTC1046IS8 Data sheet ( Hoja de datos )
| Número de pieza | LTC1046IS8 | |
| Descripción | Inductorless 5V to + 5V Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1046
“Inductorless”
5V to – 5V Converter
FEATURES
s 50mA Output Current
s Plug-In Compatible with ICL7660/LTC1044
s ROUT = 35Ω Maximum
s 300µA Maximum No Load Supply Current at 5V
s Boost Pin (Pin 1) for Higher Switching Frequency
s 97% Minimum Open-Circuit Voltage Conversion
Efficiency
s 95% Minimum Power Conversion Efficiency
s Wide Operating Supply Voltage Range: 1.5V to 6V
s Easy to Use
s Low Cost
U
APPLICATIO S
s Conversion of 5V to ± 5V Supplies
s Precise Voltage Division, VOUT = VIN/2
s Supply Splitter, VOUT = ± VS/2
DESCRIPTIO
The LTC®1046 is a 50mA monolithic CMOS switched
capacitor voltage converter. It plugs in for ICL7660/
LTC1044 in 5V applications where more output current is
needed. The device is optimized to provide high current
capability for input voltages of 6V or less. It trades off
operating voltage to get higher output current. The
LTC1046 provides several voltage conversion functions:
the input voltage can be inverted (VOUT = – VIN), divided
(VOUT =VIN/2) or multiplied (VOUT = ± nVIN).
Designed to be pin-for-pin and functionally compatible
with the ICL7660 and LTC1044, the LTC1046 provides 2.5
times the output drive capability.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Generating – 5V from 5V
+
10µF
LTC1046
1
BOOST
V+ 8
2 CAP + OSC 7
3
GND
LV 6
4 CAP – VOUT 5
5V INPUT
–5V INPUT
10µF
1046 TA01
Output Voltage vs Load Current for V + = 5V
–5
–4
ICL7660/LTC1044,
ROUT = 55Ω
–3
LTC1046,
ROUT = 27Ω
–2
TA = 25°C
–1
0
0 10 20 30 40 50
LOAD CURRENT, IL (mA)
1046 TA02
1
1 page  
LTC1046
APPLICATI S I FOR ATIO
Rewriting in terms of voltage and impedance equivalence,
( )I = V1– V2 = V1– V2.
1/ fC1 REQUIV
A new variable, REQUIV, has been defined such that
REQUIV = 1/fC1. Thus, the equivalent circuit for the switched
capacitor network is as shown in Figure 3.
REQUIV
V1
V2
REQUIV
=
1
fC1
C2 RL
1046 F03
Figure 3. Switched Capacitor Equivalent Circuit
Examination of Figure 4 shows that the LTC1046 has the
same switching action as the basic switched capacitor
building block. With the addition of finite switch ON
resistance and output voltage ripple, the simple theory,
although not exact, provides an intuitive feel for how the
device works.
BOOST
3x
(1)
OSC
(7)
OSC
V+
(8)
φ
+2
φ
SW1
CAP+
(2)
SW2
+
C1
CAP–
(4)
VOUT
(5)
C2
LV
(6)
CLOSED WHEN
V+ > 3.0V
GND
(3)
1046 F04
Figure 4. LTC1046 Switched Capacitor
Voltage Converter Block Diagram
For example, if you examine power conversion efficiency
as a function of frequency (see typical curve), this simple
theory will explain how the LTC1046 behaves. The loss,
and hence the efficiency, is set by the output impedance.
As frequency is decreased, the output impedance will
eventually be dominated by the 1/fC1 term and power
efficiency will drop. The typical curves for power effi-
ciency versus frequency show this effect for various capaci-
tor values.
Note also that power efficiency decreases as frequency
goes up. This is caused by internal switching losses which
occur due to some finite charge being lost on each
switching cycle. This charge loss per unit cycle, when
multiplied by the switching frequency, becomes a current
loss. At high frequency this loss becomes significant and
the power efficiency starts to decrease.
LV (Pin 6)
The internal logic of the LTC1046 runs between V+ and LV
(Pin 6). For V+ greater than or equal to 3V, an internal
switch shorts LV to GND (Pin 3). For V+ less than 3V, the
LV pin should be tied to ground. For V+ greater than or
equal to 3V, the LV pin can be tied to ground or left floating.
OSC (Pin 7) and BOOST (Pin 1)
The switching frequency can be raised, lowered or driven
from an external source. Figure 5 shows a functional
diagram of the oscillator circuit.
V+
BOOST
(1)
2I I
OSC SCHMITT
(7) TRIGGER
∼14pF
2I I
LV 1046 F05
(6)
Figure 5. Oscillator
5
5 Page 
PACKAGE DESCRIPTIO Dimensions in inches (milimeters) unless otherwise noted.
LTC1046
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8 765
0.228 – 0.244
(5.791 – 6.197)
0.150 – 0.157**
(3.810 – 3.988)
12
0.010
(0.254
–
–
0.020
0.508)
×
45°
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
34
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
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.
11
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| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC1046IS8.PDF ] | |
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