1
Date: 5/20/04
SP682 Micro Power Inverting Charge Pump
Copyright 2004 Sipex Corporation
Low Power Voltage Conversion
+2.4V to +5.5V Input Range
99% Voltage Conversion Efficiency
Typical 60
A Supply Current
Requires Only Three External Capacitors
Includes Low Power Shutdown Option
Ideal in Portable Applications Such As
Handheld Instruments
Cellular Phones
Personal Digital Assistants
Laptops and Notebooks
Pin Compatible Upgrade to Microchip's
TC682
SP682
Micro Power Inverting Charge Pump
TYPICAL APPLICATION CIRCUIT
Corporation
APPLICATIONS
The SP682 is a monolithic charge pump voltage converter that produces a doubled, negative
voltage from a single positive supply. The SP682 charge pump outputs a 10V voltage from
a +5V input. Three external charge pump capacitors are required to support the voltage
conversion and voltage doubling process. An internal oscillator generates a 12kHz clock
which cycles the internal switching that charges the storage and transfer capacitors. The
charge pump architecture is fabricated using a low power BiCMOS process technology.
The SP682 charge pump is ideal for low power applications requiring a typical +3V battery
source such as a lithium cell. Typical applications are handheld instruments, notebook and
laptop computers, cellular phones, and data acquisition or GP systems. The SP682 is
packaged in either 8-pin NSOIC, 8-pin MSOP for surface mount applications, and 8 Pin PDIP.
+2.4V to +5V
1
F
+
GND
V
OUT
6
V
CC
4
SP682
C1+
C1
C2+
C2
C1
C2
7
1
3
5
2
C
OUT
SD
8
V
OUT
-
LCD Display
Negative bias supply for op amps
Serial interface protocol circuits
DESCRIPTION
1
2
3
4
5
6
7
8
C1-
SP682
8 Pin MSOP
GND
VOUT
C2+
SD
C1+
C2-
VCC
2
Date: 5/20/04
SP682 Micro Power Inverting Charge Pump
Copyright 2004 Sipex Corporation
These are stress ratings only and functional operation
of the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may
affect reliability.
V
CC
...........................................................................+7V
V
OUT
........................................................................11V
Storage Temperature..........................-65C to +150C
T
A
= T
MIN
to T
MAX
and V
CC
= +5V. Charge pump cap = 3.3
F, unless otherwise noted.
MIN.
TYP.
MAX.
UNITS
CONDITIONS
SUPPLY CURRENT
CHARGE PUMP CAPACITORS: 3.3
F
I
CC
60
120
A
R
L
=
, T
A
= +25
C
200
A
R
L
=
in shutdown
1
A
T
A
= +25
O
C, SD = +5V
CHARGE PUMP OUTPUT
CHARGE PUMP CAPACITORS: 3.3
F
V
OUT
9.9
9.99
Volts
R
L
=
9.0
9.5
Volts
R
L
= 2k
SOURCE RESISTANCE
R
OUT
140
180
I
L
= 10mA, T
A
= +25
C
230
I
L
= 10mA
380
450
I
L
= 5mA, V
CC
= +2.8V
OSCILLATOR FREQUENCY
f
OSC
12
20
kHz
f
osc
= 2 X f
C1+
CONVERSION EFFICIENCY
V
OUT EFF
99
99.9
%
R
L
=
V
OUT EFF
90
95
%
R
L
= 2k
START-UP TIMING
V
OUT
Power On Delay
12
ms
R
L
= 2k
SHUTDOWN TIMING
Shutdown to V
OUT
Delay
5
ms
R
L
= 2k
SUPPLY VOLTAGE
V
CC
+2.4
+5.5
Volts
Operating Temperature Range
- C
0
+70
o
C
- E
-40
+85
o
C
ELECTRICAL CHARACTERISTICS
Power Dissipation:
8-pin NSOIC......................................500mW
8-pin MSOP......................................320mW
8-pin PDIP......................................750mW
Package Derating:
8-pin NSOIC:
JA
..................................................128
C/W
8-pin MSOP:
JA
..................................................216
C/W
8-pin PDIP:
JA
..................................................97
C/W
ABSOLUTE MAXIMUM RATINGS
3
Date: 5/20/04
SP682 Micro Power Inverting Charge Pump
Copyright 2004 Sipex Corporation
about 12kHz (20kHz maximum) which con-
serves power as opposed to higher frequency
which operation typically draws more power
from V
CC
. The external charge pump capacitors
specified are 3.3
F but the absolute minimum
should be 1
F.
EFFICIENCY INFORMATION
A charge pump theoretically produces a doubled
voltage at 100% efficiency. However in the real
world, there is a small voltage drop on the output
which reduces the output efficiency. The SP682
can usually run 99.9% efficient without driving
a load. While driving a 1k
load, the SP682
remains over 90% efficiency.
Output Voltage Efficiency = V
OUT
/ (2*V
CC
);
V
OUT
= 2*V
CC
+ V
DROP
V
DROP
= (I
OUT
)*(R
OUT
)
Power Loss = I
OUT
*(V
DROP
)
The efficiency changes as the external charge
pump capacitors are varied. Larger capacitor
values will strengthen the output and reduce
output ripple. Although smaller capacitors will
cost less and save board space, lower values will
reduce the output drive capability and also in-
crease the output ripple.
Figure 3. Charge Pump Phase 2
Figure 2. Charge Pump Phase 1
The SP682's charge pump design is a simpli-
fied version of Sipex's original patented charge
pump design (5,306,954) except that it only
generates a negative output. The charge pump
utilizes external capacitors to store the charge.
Figure 1 shows the waveform found on the
negative side of capacitor C2. There is a free
running oscillator, running at 12kHz, that con-
trols the two phases of the voltage shifting. A
description of each phase follows.
Phase 1
V
OUT
charge storage -- During this phase of
the clock cycle, the positive side of capacitors
C
1
and C
2
are initially charged to +5V. C
l
+
is
then switched to ground and the charge on C
1
is transferred to C
2
. Since C
2
+
is connected to
+5V, the voltage potential across capacitor C
2
is now 10V.
Phase 2
V
OUT
transfer -- Phase two of the clock con-
nects the negative terminal of C
2
to the V
OUT
storage capacitor and the positive terminal of
C
2
to ground, and transfers the generated l0V
to C
3
. Simultaneously, the positive side of
capacitor C
1
is switched to +5V and the nega-
tive side is connected to ground.
The oscillator frequency or clock rate for the
charge pump is designed for low power opera-
tion. The oscillator operates at a frequency of
Figure 1. Charge Pump Waveform
V
CC
= +5V
5V
5V
+5V
C
1
C
2
+
+
V
OUT
Storage Capacitor
C
3
+
V
CC
= +5V
10V
C
1
C
2
+
+
V
OUT
Storage Capacitor
C
3
+
THEORY OF OPERATION
4
Date: 5/20/04
SP682 Micro Power Inverting Charge Pump
Copyright 2004 Sipex Corporation
Table 1. R
OUT
.vs. C1, C2
Table 2. C3 .vs. V
RIPPLE
SHUTDOWN FEATURE
The SP682 charge pump includes a shutdown
feature (pin 8) which disables the charge pump
when the V
OUT
is not needed. A logic "1" will
activate the shutdown mode. If shutdown is not
needed, it can be left open where an internal
pull-down resistor will always keep the charge
pump active. Typical input current for the
shutdown pin is 3
A. The shutdown feature is
another option for conserving power in portable
applications, reducing current to only 1
A.
PARALLEL DEVICES
Multiple SP682 charge pumps can be connected
in parallel. However, the effective output resis-
tance now is the output resistance of a single
device divided by the number of devices. Con-
necting multiple pumps allows the user to save
on the storage capacitor. The charge pump
capacitors still must be separate for each device.
APPLICATIONS INFORMATION
The SP682 charge pump produces a doubled,
inverted voltage from the V
CC
input. As such, it
can serve in many applications where a negative
5V to 10V output is needed. Typical applica-
tions include powering analog switches, and
biasing LCD displays and panels.
The ESR of the charge pump capacitors also
determine the output resistance. Assuming that
switch resistances are approximately equal, the
output resistance can be derived as shown be-
low:
R
OUT
= 16*(R
SW1-4
) + 4*( ESR
C1
+ ESR
C2
) + ESR
C3
+ 1 / (f
OSC
* C1) + 1 / (f
OSC
* C2)
R
OUT
is typically 140
at +25C with VCC at
+5V using 3.3
F capacitors. The total internal
switch resistance (16*R
SW
) is approximately
90
. The table below shows the comparison of
R
OUT
versus C1&C2.
C1, C2 (
F)
ROUT (
)
0.05
4085
0.10
2084
0.47
510
1.00
285
3.30
140
4.70
125
10.00
105
22.00
94
The output voltage ripple is also affected by the
capacitors, specifically C
OUT
. Larger values
will reduce the output ripple for a given output
current load of current. The formula represen-
tation is:
V
RIPPLE
= {1 / [2 * (f
OSC
* C3)] + 2 * (ESR
C3
)} * I
OUT
To minimize the output ripple, the C
OUT
storage
capacitor can be increased to over 10
F whereas
the pump capacitors can range from 1
F to 5F.
Table 2 shows the typical V
RIPPLE
for given
C
OUT
values.
C
OUT
(
F)
V
RIPPLE
(mV)
0.50
1020
1.00
520
3.30
172
4.70
120
10.00
70
22.00
43
THEORY OF OPERATION
5
Date: 5/20/04
SP682 Micro Power Inverting Charge Pump
Copyright 2004 Sipex Corporation
PACKAGE: 8 PIN NSOIC
SEE VIEW C
1
1.65
DIMENSIONS
Minimum/Maximum
(mm)
8 Pin NSOIC
(JEDEC MS-012,
AA - VARIATION)
COMMON HEIGHT DIMENSION
A
A1
A2
b
c
L
e
E1
E
L2
L1
1.35
4.90 BSC
0.40
0.31
0.51
SYMBOL
MIN NOM MAX
0.10
-
0.25
D
1.75
1.25
0.17
0.25
6.00 BSC
3.90 BSC
1.27 BSC
1.27
1.04 REF
0.25 BSC
0
5
8
15
-
-
-
-
-
-
-
A
A2
A1
SEATING PLANE
SIDE VIEW
L1
L
1
1
Seating Plane
Gauge Plane
L2
VIEW C
TOP VIEW
e
E
E/2
E1
A
INDEX AREA
(D/2 X E1/2)
E1/2
D
b
1
8 PIN NSOIC
PACKAGE:
c
WITH PLATING
BASE METAL
b
CONTACT AREA
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