LTC1046
“Inductorless”
5V to – 5V Converter
FEATURES
s
s
s
s
s
s
DESCRIPTIO
s
s
s
s
50mA Output Current
Plug-In Compatible with ICL7660/LTC1044
R
OUT
= 35Ω Maximum
300µA Maximum No Load Supply Current at 5V
Boost Pin (Pin 1) for Higher Switching Frequency
97% Minimum Open-Circuit Voltage Conversion
Efficiency
95% Minimum Power Conversion Efficiency
Wide Operating Supply Voltage Range: 1.5V to 6V
Easy to Use
Low Cost
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 (V
OUT
= – V
IN
), divided
(V
OUT
=V
IN/
2) or multiplied (V
OUT
=
±
nV
IN
).
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.
APPLICATIO S
s
s
s
Conversion of 5V to
±
5V Supplies
Precise Voltage Division, V
OUT
= V
IN
/2
Supply Splitter, V
OUT
=
±
V
S
/2
TYPICAL APPLICATIO
Output Voltage vs Load Current for V
+
= 5V
–5
Generating – 5V from 5V
–4
OUTPUT VOLTAGE (V)
LTC1046
1
2
BOOST
CAP
+
GND
CAP
–
8
V
+
OSC
LV
V
OUT
7
6
5
–5V INPUT
10µF
5V INPUT
–3
ICL7660/LTC1044,
R
OUT
= 55Ω
LTC1046,
R
OUT
= 27Ω
+
10µF
3
4
–2
–1
1046 TA01
0
0
10
20
30
40
LOAD CURRENT, I
L
(mA)
50
1046 TA02
U
T
A
= 25°C
+
U
U
1
LTC1046
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
BOOST 1
CAP
+
2
GND 3
CAP
–
4
J8 PACKAGE
8-LEAD CERDIP
8
7
6
5
V
+
OSC
LV
V
OUT
Supply Voltage ....................................................... 6.5V
Input Voltage on Pins 1, 6 and 7
(Note 2) ............................ – 0.3 < V
IN
< (V
+
) + 0.3V
Current into Pin 6 .................................................. 20µA
Output Short Circuit Duration
(V
+
≤
6V) ............................................... Continuous
Operating Temperature Range
LTC1046C .................................... 0°C
≤
T
A
≤
70°C
LTC1046I ................................. – 40°C
≤
T
A
≤
85°C
LTC1046M .................................... – 55°C to 125°C
Storage Temperature Range ............... – 65°C to + 150°C
Lead Temperature (Soldering, 10 sec.)................. 300°C
ORDER PART
NUMBER
LTC1046CN8
LTC1046CS8
LTC1046IN8
LTC1046IS8
LTC1046MJ8
S8 PART MARKING
1046
1046I
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 160°C,
θ
JA
= 100°C (J8)
T
JMAX
= 110°C,
θ
JA
= 130°C (N8)
T
JMAX
= 150°C,
θ
JA
= 150°C (S8)
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 5V, C
OSC
= 0pF, unless otherwise noted.
SYMBOL PARAMETER
I
S
Supply Current
CONDITIONS
R
L
=
∞,
Pins 1 and 7 No Connection
R
L
=
∞,
Pins 1 and 7 No Connection,
V
+
= 3V
R
L
= 5kΩ
R
L
= 5kΩ
V
+
= 5V, I
L
= 50mA (Note 3)
V
+
f
OSC
P
EFF
V
OUTEFF
I
OSC
Oscillator Frequency
Power Efficiency
Voltage Conversion
Efficiency
Oscillator Sink or Source
Current
= 2V, I
L
= 10mA
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
LTC1046C
TYP
MAX
165
35
300
MIN
LTC1046I/M
TYP
MAX
165
35
300
UNITS
µA
µA
V
V
+L
V
+H
R
OUT
Minimum Supply Voltage
Maximum Supply Voltage
Output Resistance
1.5
6
27
27
60
20
4
95
97
30
5.5
97
99.9
35
45
85
1.5
6
27
27
60
20
4
95
97
30
5.5
97
99.9
35
50
90
V
+
= 5V (Note 4)
V
+
= 2V
R
L
= 2.4kΩ
R
L
=
∞
V
OSC
= 0V or V
+
Pin 1 = 0V
Pin 1 = V
+
q
q
4.2
15
35
45
4.2
15
40
50
Note 1:
Absolute Maximum Ratings are those values beyond which
the life of the device may be impaired.
Note 2:
Connecting any input terminal to voltages greater than V
+
or
less than ground may cause destructive latch-up. It is recommended
that no inputs from sources operating from external supplies be
applied prior to power-up of the LTC1046.
Note 3:
R
OUT
is measured at T
J
= 25°C immediately after power-on.
Note 4:
f
OSC
is tested with C
OSC
= 100pF to minimize the effects of test
fixture capacitance loading. The 0pF frequency is correlated to this 100pF
test point, and is intended to simulate the capacitance at pin 7 when the
device is plugged into a test socket and no external capacitor is used.
2
U
V
Ω
Ω
Ω
kHz
kHz
%
%
µA
µA
W
U
U
W W
W
LTC1046
TYPICAL PERFOR A CE CHARACTERISTICS
Output Resistance vs
Oscillator Frequency
500
T
A
= 25°C
V
+
= 5V
I
L
= 10mA
1000
OUTPUT RESISTANCE, R
O
(Ω)
OUTPUT RESISTANCE, R
O
(Ω)
400
OUTPUT RESISTANCE (Ω)
300
C1 = C2
= 10µF
C1 = C2
= 1µF
C1 = C2
= 100µF
200
100
0
100
1k
10k
OSCILLATOR FREQUENCY, f
OSC
(Hz)
1046 G01
Power Conversion Efficiency vs
Load Current for V
+
= 2V
POWER CONVERSION EFFICIENCY, P
EFF
(%)
POWER CONVERSION EFFICIENCY, P
EFF
(%)
100
90
80
70
60
50
40
30
20
10
0
0
1
2
T
A
= 25°C
V
+
= 2V
C1 = C2 = 10µF
f
OSC
= 8kHz
3 4 5 6 7 8
LOAD CURRENT, I
L
(mA)
9
10
I
S
P
EFF
10
9
8
SUPPLY CURRENT (mA)
7
6
5
4
3
2
1
0
100
90
80
70
60
50
40
30
20
10
0
POWER CONVERSION EFFICIENCY, P
EFF
(%)
Output Voltage vs Load Current
for V
+
= 2V
2.5
T
A
= 25°C
2.0 V
+
= 2V
f
OSC
= 8kHz
1.5 C1 = C2 = 10µF
1.0
0.5
0.0
–0.5
–1.0
–1.5
–2.0
–2.5
0
2
4
6 8 10 12 14 16 18 20
LOAD CURRENT, I
L
(mA)
1046 G07
3
OSCILLATOR FREQUENCY, f
OSC
(kHz)
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
SLOPE = 52Ω
–4
–5
0
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT, I
L
(mA)
1046 G08
U W
1046 G04
(Using Test Circuit in Figure 1)
Output Resistance vs
Temperature
80
70
60
50
40
30
20
V
+
= 5V, C
OSC
= 0pF
V
+
= 2V, C
OSC
= 0pF
C1 = C2 = 10µF
Output Resistance vs
Supply Voltage
T
A
= 25°C
I
L
= 3mA
100
C
OSC
= 100pF
C
OSC
= 0pF
100k
10
0
1
2
3
4
5
6
7
SUPPLY VOLTAGE, V
+
(V)
1046 G02
10
–55
–25
0
75 100
25
50
AMBIENT TEMPERATURE (°C)
125
1046 G03
Power Conversion Efficiency vs
Load Current for V
+
= 5V
100
P
EFF
90
80
SUPPLY CURRENT (mA)
70
60
50
I
S
40
30
T
A
= 25°C
V
+
= 5V
C1 = C2 = 10µF
f
OSC
= 30kHz
0
10
20
50
30
40
LOAD CURRENT, I
L
(mA)
60
70
20
10
0
100
98
96
94
92
90
88
86
84
82
Power Conversion Efficiency vs
Oscillator Frequency
A
A = 100µF, 1mA
B = 100µF, 15mA
C = 10µF, 1mA
D = 10µF, 15mA
E = 1µF, 1mA
F = 1µF, 15mA
B
E
V
+
= 5V
T
A
= 25°C
C1 = C2
C
D
F
80
100
1k
10k
100k
OSCILLATOR FREQUENCY, f
OSC
(Hz)
1M
1046 G05
1046 G06
Output Voltage vs Load Current
for V
+
= 5V
5
4
100
Oscillator Frequency as a
Function of C
OSC
V
+
= 5V
T
A
= 25°C
PIN 1 = V
+
10
T
A
= 25°C
V
+
= 5V
f
OSC
= 30kHz
C1 = C2 = 10µF
2
1
0
–1
–2
–3
SLOPE = 27Ω
PIN 1 = OPEN
1
0.1
10
100
10000
1000
1
EXTERNAL CAPACITOR (PIN 7 TO GND), C
OSC
(pF)
1046 G09
3
LTC1046
TYPICAL PERFOR A CE CHARACTERISTICS
Oscillator Frequency as a
Function of Supply Voltage
100
T
A
= 25°C
C
OSC
= 0pF
OSCILLATOR FREQUENCY, f
OSC
(kHz)
OSCILLATOR FREQUENCY, f
OSC
(kHz)
10
1
0
1
2
3
6
4
5
AMBIENT TEMPERATURE (°C)
7
TEST CIRCUIT
LTC1046
1
2
BOOST
CAP
+
GND
CAP
–
Figure 1
APPLICATI
S I FOR ATIO
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:
∆q
= q1 – q2 = C1(V1 – V2).
If the switch is cycled “f” times per second, the charge
transfer per unit time (i.e., current) is:
I = f •
∆q
= f • C1(V1 – V2).
V1
f
R
L
C1
C2
1046 F02
Figure 2. Switched Capacitor Building Block
4
+
U
W
U W
+
C1
10µF
(Using Test Circuit in Figure 1)
Oscillator Frequency vs
Temperature
40
38
36
34
32
30
28
26
–55
V
+
= 5V
C
OSC
= 0pF
–25
0
75 100
25
50
AMBIENT TEMPERATURE (°C)
125
1046 G10
1046 G11
V
+
(5V)
8
V
+
OSC
LV
V
OUT
7
6
5
C
OSC
EXTERNAL
OSCILLATOR
R
L
I
S
3
4
I
L
V
OUT
C2
10µF
1046 F01
U
UO
V2
LTC1046
APPLICATI
I
=
V1 – V 2
S I FOR ATIO
Rewriting in terms of voltage and impedance equivalence,
(
1 / fC1
)
=
V1 – V 2
.
R
EQUIV
A new variable, R
EQUIV
, has been defined such that
R
EQUIV
= 1/fC1. Thus, the equivalent circuit for the switched
capacitor network is as shown in Figure 3.
R
EQUIV
V1
C2
R
EQUIV
= 1
fC1
R
L
V2
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.
V
+
(8)
BOOST
3x
(1)
OSC
OSC
(7)
+2
φ
CAP –
(4)
V
OUT
(5)
C2
LV
(6)
φ
SW1
CAP +
(2)
SW2
+
C1
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.
+
U
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
+
2I
BOOST
(1)
I
OSC
(7)
∼14pF
2I
LV
(6)
I
1046 F05
W
U
UO
SCHMITT
TRIGGER
Figure 5. Oscillator
5
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