LT1026
Voltage Converter
FEATURES
s
s
s
s
s
s
s
s
DESCRIPTIO
Generates + and – from Single Input
Up to
±18V
Output
Only Needs Four 1µF Capacitors
No Inductors
10mA Output Current Minimum
Operates Down to 4V
No Latchup
8-Pin Minidip
The LT
®
1026 is a switched capacitor voltage doubler and
inverter on a single monolithic die. Capable of operating
from a 4V to 10V input, it provides
±7V
to
±18V
output.
Output currents of over 10mA are available. Two charge
pumps first double the input voltage then invert the
doubled voltage. Manufactured in bipolar technology, the
LT1026 is not susceptible to latchup and generates up to
36V.
The LT1026 offers a convenient way of generating addi-
tional system voltages without using inductors. Powering
interface circuits, op amps or data acquisition circuitry off
logic supplies is simplified. Other Linear Technology
voltage converters such as the low power LTC
®
1044
CMOS and 100mA bipolar LT1054 are available.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIONS
s
s
s
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Line Drivers
Op Amp Suppliers
Battery Splitters
RS232 Power
TYPICAL APPLICATION
Voltage Doubler and Inverter
C1
1µF
10
8
6
C = 1µF
V
IN
= 5V
T
A
= 25°C
OUTPUT VOLTAGE (V)
1
2
C2
1µF
–V
OUT
C1
–
C2
+
LT1026
C2
–
–V
OUT
+V
OUT
C1
+
V
IN
GND
8
7
6
5
V
IN
4
2
0
–2
–4
–6
–8
–10
+
+V
OUT
1µF
+
3
4
1µF
1026 • TA01
0
U
Output Voltage
5
15
20
10
LOAD CURRENT (mA)
25
LT1026 • TA02
U
U
+
+
1
LT1026
ABSOLUTE
MAXIMUM
RATINGS
Supply Voltage ........................................................ 10V
V
+
............................................................................ 20V
V
–
..........................................................................– 20V
Short-Circuit Duration ......................................... 10 sec
Operating Temperature Range
LT1026C ................................................. 0°C to 70°C
LT1026I .............................................. – 40°C to 85°C
LT1026M .......................................... – 55°C to 125°C
Lead Temperature (Soldering, 10 sec)................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
+V
OUT
C1
–
1
C2
+
2
C2
–
3
5
4
–V
OUT
8
7 C1
6
+
ORDER PART
NUMBER
V
IN
GND
LT1026CH
LT1026MH
H PACKAGE
8-LEAD TO-5 METAL CAN
T
JMAX
= 150°C,
θ
JA
= 150°C/W (H8)
ELECTRICAL CHARACTERISTICS
PARAMETERS
Output Voltage
CONDITIONS
V
IN
= 4V
(Note 1)
I
L
= 0mA
I
L
= 0mA
I
L
= 10mA
I
L
= – 10mA
I
L
= 15mA
I
L
= – 15mA
I
L
= 0mA
I
L
= 0mA
I
L
= 10mA
I
L
= – 10mA
I
L
= 15mA
I
L
= – 15mA
I
L
= 10mA, – 10mA
I
L
= 10mA, – 10mA
I
L
= 0mA
I
L
= 0mA
Positive
Negative
Positive
Negative
Positive
Negative
Positive
Negative
Positive
Negative
Positive
Negative
Positive
Negative
Positive
Negative
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
V
IN
= 5V
V
IN
= 10V
V
IN
= 5V
V
IN
= 10V
Supply Current
V
IN
= 4V
V
IN
= 10V
The
q
denotes specifications which apply over the specified operating
temperature range. Loads are applied to individual outputs unless otherwise
marked.
Note 1:
V
IN
min = – 4.5 for T
A
≤
40°C
2
U
U
W
W W
U
W
TOP VIEW
C1
–
1
C2
+
2
C2
–
3
–V
OUT
4
J8 PACKAGE
8-LEAD CERAMIC DIP
8 +V
OUT
7 C1
+
6 V
IN
5 GND
N8 PACKAGE
8-LEAD PLASTIC DIP
ORDER PART
NUMBER
LT1026CJ8
LT1026CN8
LT1026CS8
LT1026IS8
LT1026MJ8
S8 PART MARKING
1026
1026I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 150°C/W (J8)
T
JMAX
= 150°C,
θ
JA
= 100°C/W (N8)
T
JMAX
= 150°C,
θ
JA
= 150°C/W (S8)
MIN
6.5
–6
5.25
– 4.5
6.25
– 5.5
18
– 17.7
16
– 15.3
15.25
– 14.5
6.25
– 5.5
15
– 14.25
TYP
7
– 6.7
5.7
–5
7
– 6.2
18.5
– 18
17.6
– 17
17
– 16.5
7.2
– 6.5
16.8
– 15.75
7
15
MAX
UNITS
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
12.5
30
mA
mA
LT1026
TYPICAL PERFORMANCE CHARACTERISTICS
Load Regulation (Both Outputs
Loaded)
10
8
6
C = 1µF
V
IN
= 5V
T
A
= 25°C
10
8
6
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
4
2
0
–2
–4
–6
–8
–10
0
5
15
20
10
LOAD CURRENT (mA)
25
4
2
0
–2
–4
–6
–8
–10
0
5
I
L
= 0
C = 1µF
V
IN
= 5V
T
A
= 25°C
OUTPUT VOLTAGE (V)
Supply Current
90
75
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
60
45
30
15
0
0
40
30
20
10
0
SUPPLY CURRENT (mA)
C = 22µF
V
IN
= 5V
T
A
= 25°C
BOTH OUTPUTS
LOADED
5
10
15
20
OUTPUT CURRENT (mA)
Ripple
60
50
40
30
20
10
0
1.0
2.2
4.7
10
22
47
OUTPUT CAPACITOR (µF)
100
V
IN
= 5V
I
L
= 5mV
BOTH OUTPUTS
10
8
6
OUTPUT VOLTAGE (V)
RIPPLE (mV
P-P
)
U W
LT1026 • TPC01
Load Regulation for Positive
Loading
10
8
6
4
2
0
–2
–4
–6
–8
–10
25
Load Regulation for Negative
Loading
I
L
= 0
C = 1µF
V
IN
= 5V
T
A
= 25°C
15
20
10
LOAD CURRENT (mA)
0
5
15
20
10
LOAD CURRENT (mA)
25
LT1026 • TPC02
LT1026 • TPC03
Supply Current
60
50
C = 22µF
V
IN
= 5V
T
A
= 25°C
NEGATIVE
OUTPUT
LOADED
60
50
40
30
20
10
0
0
5
10
15
20
OUTPUT CURRENT (mA)
25
Supply Current
C = 22µF
V
IN
= 5V
T
A
= 25°C
POSITIVE
OUTPUT
LOADED
25
0
5
10
15
20
OUTPUT CURRENT (mA)
25
LT1026 • TPC04
LT1026 • TPC05
LT1026 • TPC06
Output Voltage vs Temperature
4
2
0
–2
–4
–6
–8
–10
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
C = 22µF
V
IN
= 5V
I
L
= 1mA
1026 • TPC07
LT1026 • TPC08
3
LT1026
APPLICATIONS INFORMATION
The LT1026 is a nonregulating voltage converter that
converts a single input voltage into both a positive and
negative output at up to 15mA. A positive input voltage is
first doubled and then the doubled voltage is inverted. The
voltage output level is dependent on both the input voltage
and the output loading. The total output current available
depends on the individual loading of the outputs since
loading on one output affects the load and the voltage of
the other.
Only four external components are needed for operation.
Two charge pump capacitors and two output storage
capacitors. Nominal value for these capacitors is 1µF, but
the LT1026 will operate (with reduced performance) down
to 0.1µF. Higher value capacitors (22µF) will reduce ripple
and slightly lower output impedance. For higher output
currents the outputs of several converters may be paral-
leled with common output capacitors.
The substrate diodes are an inherent part of the IC, and
must always be reversed biased to isolate the individual
transistors. In the LT1026 the substrate is tied to the
negative output. If the negative output is not used, such as
when only the voltage doubler output is needed, – V
OUT
must be tied to ground so the substrate diodes are
properly biased. The substrate diodes must never become
forward biased even during overload conditions. For ex-
ample, pulling – V
OUT
positive with respect to ground can
forward bias the substrate diodes. Clamping the substrate
to ground with an external diode would be needed to
ensure proper operation and prevent the substrate from
carrying any current.
No overload protection is included on the LT1026. Neither
output is damaged by momentary shorts, but during
sustained shorts the resulting high current flow will over-
heat the IC.
TYPICAL APPLICATIONS
Positive to Negative Converter
–V
OUT
1µF
1
2
C1
–
C2
+
LT1026
C2
–
–V
OUT
V
IN
GND
+V
OUT
C1
+
8
7
6
5
V
IN
NC
+
1µF
3
4
4
U
W
+
U
U
U
1026 • TA03
Voltage Doubler
1µF
+
1
2
3
4
C1
–
C2
+
LT1026
C2
–
–V
OUT
+V
OUT
C1
+
V
IN
GND
8
7
6
5
V
IN
+
V
OUT
1µF
1026 • TA04
LT1026
TYPICAL APPLICATIONS
Standard Configuration Voltage Doubler and Inverter
C1
1µF
C2
1µF
+
3
4
Parallel Converters for Higher Output Current and Lower Output Impedance
C1
1µF
C1
1µF
1
2
C2
1µF
C1
–
C2
+
LT1026
C2
–
–V
OUT
+V
OUT
C1
+
V
IN
GND
+
3
4
+
+
U
+
1
2
C2
1µF
–V
OUT
C1
–
C2
+
LT1026
C2
–
–V
OUT
+V
OUT
C1
+
V
IN
GND
8
7
6
5
V
IN
+
+V
OUT
1µF
+
3
4
1µF
1026 • TA05
Voltage Quadrupler
C1
1µF
+
1
2
C1
–
C2
+
LT1026
C2
–
–V
OUT
+V
OUT
C1
+
V
IN
GND
8
7
6
5
+
+V
OUT
1µF
V
IN
(FLOATING)
1µF
+
1026 • TA06
+
8
7
6
5
V
IN
C2
1µF
1
2
C1
–
C2
+
+
+V
OUT
C1
+
LT1026
C2
–
–V
OUT
V
IN
GND
8
7
6
5
V
IN
+
+V
OUT
1µF
+
3
4
1026 • TA07
–V
OUT
1µF
5
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