LTC660
100mA CMOS
Voltage Converter
FEATURES
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DESCRIPTION
The LTC
®
660 is a monolithic CMOS switched-capacitor
voltage converter. It performs supply voltage conversion
from positive to negative from an input range of 1.5V to
5.5V, resulting in complementary output voltages of
– 1.5V to – 5.5V. It also performs a doubling at an input
voltage range of 2.5V to 5.5V, resulting in a doubled
output voltage of 5V to 11V. Only two external capacitors
are needed for the charge pump and charge reservoir
functions.
The converter has an internal oscillator that can be
overdriven by an external clock or slowed down when
connected to a capacitor. The oscillator runs at a 10kHz
frequency when unloaded. A higher frequency outside the
audio band can also be obtained if the BOOST pin is tied
to V
+
.
The LTC660 contains an internal oscillator, divide-by-two,
voltage level shifter and four power MOSFETs.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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Simple Conversion of 5V to – 5V Supply
Output Drive: 100mA
R
OUT
: 6.5
Ω
(0.65V Loss at 100mA)
BOOST Pin (Pin 1) for Higher Switching Frequency
Inverting and Doubling Modes
Minimum Open Circuit Voltage Conversion
Efficiency: 99%
Typical Power Conversion Efficiency
with a 100mA Load: 88%
Easy to Use
APPLICATIONS
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Conversion of 5V to
±5V
Supplies
Inexpensive Negative Supplies
Data Acquisition Systems
High Current Upgrade to LTC1044 or LTC7660
TYPICAL APPLICATION
Generating – 5V from 5V
1
2
BOOST
V
+
8
Output Voltage vs
Load Current for V
+
= 5V
–5.0
5V INPUT
4
CAP
–
V
OUT
5
OUTPUT VOLTAGE (V)
+
C1
150µF
7
CAP
+
OSC
LTC660
6
3
GND
LV
–5V
OUTPUT
–4.8
–4.6
C2
150µF
–4.4
660 TA01
–4.2
–4.0
0
20
60
80
40
LOAD CURRENT (mA)
100
660 TA02
U
+
U
U
T
A
= 25°C
R
OUT
= 6.5Ω
1
LTC660
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
6V
BOOST 1
CAP
+
2
GND 3
CAP
–
4
TOP VIEW
8 V
+
7 OSC
6 LV
5 V
OUT
Supply Voltage (V
+
) ..................................................
ORDER PART
NUMBER
LTC660CN8
LTC660CS8
S8 PART MARKING
660
Input Voltage on Pins 1, 6, 7
(Note 2) ............................ – 0.3V < V
IN
< (V
+
+ 0.3V)
Output Short-Circuit Duration to GND
(Note 5) ............................................................. 1 sec
Power Dissipation.............................................. 500mW
Operating Temperature Range .................... 0°C to 70°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
N8 PACKAGE
8-LEAD PLASTIC DIP
S8 PACKAGE
8-LEAD PLASTIC SOIC
T
JMAX
= 100°C,
θ
JA
= 100°C/W (N)
T
JMAX
= 100°C,
θ
JA
= 150°C/W (S)
Consult Factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
V
+
= 5V, C1 and C2 = 150µF, Boost = Open, C
OSC
= 0pF, T
A
= 25°C, unless otherwise noted.
SYMBOL PARAMETER
Supply Voltage
CONDITIONS
R
L
= 1k
Inverter, LV = Open
Inverter, LV = GND
Doubler, LV = V
OUT
Boost = Open
Boost = V
+
q
q
q
q
q
q
q
MIN
3
1.5
2.5
TYP
MAX
5.5
5.5
5.5
UNITS
V
V
V
mA
mA
mA
Ω
kHz
kHz
%
%
%
%
µA
µA
I
S
I
OUT
R
OUT
f
OSC
Supply Current
Output Current
Output Resistance
Oscillator Frequency
Power Efficiency
No Load
0.08
0.23
100
6.5
10
80
0.5
3
10
V
OUT
More Negative Than – 4V
I
L
= 100mA (Note 3)
Boost = Open
Boost = V
+
(Note 4)
R
L
= 1k Connected Between V
+
and V
OUT
R
L
= 500Ω Connected Between V
OUT
and GND
I
L
= 100mA to GND
No Load
Boost = Open
Boost = V
+
q
q
96
92
99
98
96
88
99.96
±1.1
±5.0
Voltage Conversion Efficiency
Oscillator Sink or Source Current
The
q
denotes specifications which apply over the full operating
temperature range; all other limits and typicals are at T
A
= 25°C.
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a 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 source operating from external supplies be applied prior to
power-up of the LTC660.
Note 3:
The output resistance is a combination of internal switch
resistance and external capacitor ESR. To maximize output voltage and
efficiency, keep external capacitor ESR < 0.2Ω.
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.
Note 5:
OUT may be shorted to GND for 1 sec without damage, but
shorting OUT to V
+
may damage the device and should be avoided. Also,
for temperatures above 85°C, OUT must not be shorted to GND or V
+
,
even instantaneously, or device damage may result.
2
U
W
U
U
W W
W
LTC660
TYPICAL PERFORMANCE CHARACTERISTICS
(Using Test Circuit in Figure 1)
Supply Current vs Supply Voltage
300
T
A
= 25°C
250
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
OUTPUT RESISTANCE (Ω)
200
150
BOOST = V
+
100
BOOST = OPEN
50
0
1.5
2
4 4.5
2.5 3 3.5
SUPPLY VOLTAGE (V)
Output Resistance
vs Supply Voltage
18
16
25
T
A
= 25°C
BOOST = OPEN
OUTPUT RESISTANCE (Ω)
OUTPUT RESISTANCE (Ω)
14
12
10
8
6
4
2
0
0
1
3
4
2
SUPPLY VOLTAGE (V)
5
6
OUTPUT VOLTAGE (V)
Efficiency vs Load Current
100
95
90
T
A
= 25°C
BOOST = OPEN
V
+
= 5.5V
V
+
= 4.5V
V
+
= 3.5V
100
95
90
OUTPUT VOLTAGE DROP FROM
SUPPLY VOLTAGE (V)
EFFICIENCY (%)
85
80
75
70
V = 1.5V
65
60
0
+
+
EFFICIENCY (%)
V = 2.5V
65
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
LTC660 • TPC07
U W
5
LTC660 • G01
LTC690 • TPC04
Supply Current
vs Oscillator Frequency
1000
T
A
= 25°C
V
+
= 5V
100
90
80
70
60
50
40
30
20
10
5.5
Output Resistance
vs Oscillator Frequency
T
A
= 25°C
V
+
= 5V
BOOST = OPEN
100
C1 = C2 = 150µF
C1 = C2 = 1500µF
C1 = C2 = 22µF
10
1
0.01
0.1
100
1
10
OSCILLATOR FREQUENCY (kHz)
1000
0
0.1
1
10
OSCILLATOR FREQUENCY (kHz)
100
LTC660 • G02
LTC660 • TPC03
Output Resistance vs Temperature
–3.0
BOOST = OPEN
20
V
+
= 1.5V
15
V = 3V
10
V
+
= 5V
5
+
Output Voltage and Efficiency
vs Load Current, V
+
= 5V
100
T
A
= 25°C
BOOST = OPEN
–3.4
LTC660
EFFICIENCY
96
92
88
84
80
–4.2
LTC660
OUTPUT VOLTAGE
76
72
68
64
EFFICIENCY (%)
–3.8
–4.6
0
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
LTC660 • TPC05
–5.0
0
60
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
LTC660 • TPC06
Efficiency vs Load Current
T
A
= 25°C
BOOST = V
+
V
+
= 5.5V
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
LTC660 • TPC08
Output Voltage Drop
vs Load Current
T
A
= 25°C
BOOST = OPEN
V
+
= 2.5V
V
+
= 1.5V
85
80
75
70
V
+
= 4.5V
V
+
= 3.5V
V
+
= 2.5V
V
+
= 1.5V
V
+
= 3.5V
V
+
= 4.5V
V
+
= 5.5V
60
0
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
LTC660 • TPC09
3
LTC660
TYPICAL PERFORMANCE CHARACTERISTICS
(Using Test Circuit in Figure 1)
Output Voltage Drop
vs Load Current
1.0
0.9
T
A
= 25°C
BOOST = V
+
OUTPUT VOLTAGE DROP FROM
SUPPLY VOLTAGE (V)
0.8
OUTPUT VOLTAGE (V)
0.6
0.5
0.4
0.3
0.2
0.1
0
0
V
+
= 1.5V
V
+
= 2.5V
EFFICIENCY (%)
0.7
V
+
= 5.5V
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
LTC660 • TPC10
Oscillator Frequency
vs Supply Voltage
12
T
A
= 25°C
BOOST = OPEN
OSC = OPEN
OSCILLATOR FREQUENCY (kHz)
OSCILLATOR FREQUENCY (kHz)
8
6
4
2
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
LTC660 • TPC13
70
60
50
40
30
20
10
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
LTC660 • TPC14
OSCILLATOR FREQUENCY (kHz)
10
Oscillator Frequency
vs Temperature
100
90
100
OSCILLATOR FREQUENCY (kHz)
OSCILLATOR FREQUENCY (kHz)
80
70
60
50
40
30
20
10
V
+
= 5V
BOOST = V
+
OSC = OPEN
0
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
LTC660 • TPC16
4
U W
V = 4.5V
V
+
= 3.5V
+
Output Voltage
vs Oscillator Frequency
–5.0
I
L
= 1mA
–4.5
I
L
= 10mA
–4.0
I
L
= 80mA
–3.5
100
95
90
85
80
75
70
65
–3.0
T
A
=25°C
V
+
= 5V
BOOST = OPEN
0.1
1
10
OSCILLATOR FREQUENCY (kHz)
100
60
55
Efficiency vs Oscillator Frequency
I
L
= 10mA
I
L
= 80mA
I
L
= 1mA
–2.5
50
0.1
T
A
= 25°C
V
+
= 5V
BOOST = OPEN
1
10
OSCILLATOR FREQUENCY (kHz)
100
LTC660 • TPC11
LTC660 • TPC12
Oscillator Frequency
vs Supply Voltage
100
T
A
= 25°C
90 BOOST = V
+
OSC = OPEN
80
12
10
8
6
4
2
Oscillator Frequency
vs Temperature
V
+
= 5V
BOOST = OPEN
OSC = OPEN
0
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
LTC660 • TPC15
Oscillator Frequency
vs External Capacitance
10
BOOST = V
+
1
0.1
BOOST = OPEN
00.1
1
10
100
1000
CAPACITANCE (pF)
10000
LTC660 • TPC17
LTC660
PIN FUNCTIONS
PIN
1
NAME
BOOST
INVERTER
Internal Oscillator Frequency Control Pin.
BOOST = Open, f
OSC
= 10kHz typ;
BOOST = V
+
, f
OSC
= 80kHz typ; when OSC is driven
externally BOOST has no effect.
Positive Terminal for Charge Pump Capacitor
Power Supply Ground Input
Negative Terminal for Charge Pump Capacitor
Negative Voltage Output
Tie LV to GND when the input voltage is less than 3V.
LV may be connected to GND or left open for input
voltages above 3V. Connect LV to GND when
overdriving OSC.
An external capacitor can be connected to this pin to
slow the oscillator frequency. Keep stray capacitance
to a minimum. An external oscillator can be applied
to this pin to overdrive the internal oscillator.
Positive Voltage Input
DOUBLER
Same
2
3
4
5
6
CAP
+
GND
CAP
–
V
OUT
LV
7
OSC
8
V
+
TEST CIRCUIT
V
+
1
2
LTC660
8
7
6
5
I
S
V
+
5V
C
OSC
R
L
I
L
C1
150µF
V
OUT
LTC660 • F01
Figure 1. Test Circuit
+
U
U
U
Same
Positive Voltage Input
Same
Power Supply Ground Input
LV must be tied to V
OUT
for all input voltages.
Same except standard logic levels will not be able to
overdrive OSC pin.
Positive Voltage Output
+
C1
150µF
3
4
EXTERNAL
OSCILLATOR
5
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