REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
a
ADM8828/ADM8829
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999
Switched-Capacitor
Voltage Inverter with Shutdown
FUNCTIONAL BLOCK DIAGRAMS
TOP VIEW
(Not to Scale)
OUT
IN
CAP
CAP+
SHDN
GND
ADM8828
1
2
3
6
5
4
TOP VIEW
(Not to Scale)
OUT
IN
CAP+
NC
GND
ADM8829
1
2
3
6
5
4
CAP
NC = NO CONNECT
FEATURES
Inverts Input Supply Voltage
99% Voltage Conversion Efficiency
25 mA Output Current
Shutdown Function
Requires Only Two Capacitors
1 F Capacitors
18
Output Resistance
+1.5 V to +5.5 V Input Range
600 A Quiescent Current
20 nA Shutdown Current (ADM8828)
APPLICATIONS
Handheld Instruments
LCD Panels
Cellular Phones
PDAs
Remote Data Acquisition
Op Amp Power Supplies
GENERAL DESCRIPTION
The ADM8828/ADM8829 is a charge-pump voltage inverter
which may be used to generate a negative supply from a positive
input. Input voltages ranging from +1.5 V to +5.5 V can be
inverted into a negative 1.5 V to 5.5 V output supply. This
inverting scheme is ideal for generating a negative rail in single
power-supply systems. Only two small external capacitors are
needed for the charge pump. Output currents up to 25 mA with
greater than 99% efficiency are achievable.
The ADM8828 also features a low power shutdown (SHDN)
pin. This can be used to disable the device and reduce the quies-
cent current to 20 nA.
The ADM8828/ADM8829 is available in a 6-lead SOT-23
package.
+
+
+1.5V TO +5.5V
INPUT
SHUTDOWN
CONTROL
C1
1 F
C2
1 F
INVERTED
NEGATIVE
OUTPUT
ADM8828/
ADM8829
CAP+
CAP
GND
IN
SHDN
OUT
Figure 1. Typical Circuit Configuration
2
REV. A
ADM8828/ADM8829SPECIFICATIONS
(V
IN
= +5 V, C1, C2 = 1 F,
1
T
A
= T
MIN
to T
MAX
unless other-
wise noted)
Parameter
Min
Typ
Max
Units
Test Conditions/Comments
Input Voltage, IN
1.5
5.5
V
R
L
= 10 k
Supply Current
600
1000
µ
A
Unloaded
Output Current
25
mA
Output Resistance
18
28
I
L
= 5 mA
Output Ripple
25
mV p-p
I
L
= 5 mA
130
mV p-p
I
L
= 25 mA
Charge-Pump Frequency
50
120
190
kHz
65
kHz
V
IN
= +2.25 V
Power Efficiency
90
%
R
L
= 200
87
%
R
L
= 1 k
Voltage Conversion Efficiency
99.5
99.96
%
No Load
98
%
R
L
= 1 k
91
%
R
L
= 200
Shutdown Supply Current, I
SHDN
0.02
2
µ
A
SHDN = IN
Shutdown Input Voltage, V
SHDN
2.0
V
SHDN High = Disabled
0.8
V
SHDN Low = Enabled
Shutdown Exit Time
175
µ
s
I
L
= 5 mA
NOTES
1
C1 and C2 are low ESR (<0.2
) electrolytic capacitors. High ESR will degrade performance.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS*
(T
A
= +25
°
C unless otherwise noted)
Input Voltage (IN to GND) . . . . . . . . . . . . . . . 0.3 V to +6 V
OUT to GND . . . . . . . . . . . . . . . . . . . . . . . . 6.0 V to +0.3 V
OUT, IN Output Current (Continuous) . . . . . . . . . . . . 50 mA
Output Short Circuit Duration to GND . . . . . . . . . . . 10 secs
Power Dissipation, RT-6 . . . . . . . . . . . . . . . . . . . . . . 570 mW
(Derate 8.3 mW/
°
C above +70
°
C)
JA
, Thermal Impedance . . . . . . . . . . . . . . . . . . . . 120
°
C/W
Operating Temperature Range
Industrial (A Version) . . . . . . . . . . . . . . . . 40
°
C to +85
°
C
Storage Temperature Range . . . . . . . . . . . 65
°
C to +150
°
C
Lead Temperature Range (Soldering 10 sec) . . . . . . . . +300
°
C
Vapor Phase (70 sec) . . . . . . . . . . . . . . . . . . . . . . . . +215
°
C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . +220
°
C
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . >3500 V
*This is a stress rating only and functional operation of the device at these or any
other conditions above those indicated in the operation section of this specification
is not implied. Exposure to absolute maximum rating conditions for extended
periods may affect device reliability.
ORDERING GUIDE
Temperature
Branding
Package
Model
Range
Information
Option*
ADM8828ART
40
°
C to +85
°
C
MM0
RT-6
ADM8829ART
40
°
C to +85
°
C
MN0
RT-6
*RT-6 = 6-lead SOT-23.
PIN CONFIGURATIONS
TOP VIEW
(Not to Scale)
OUT
IN
CAP
CAP+
SHDN
GND
ADM8828
1
2
3
6
5
4
TOP VIEW
(Not to Scale)
OUT
IN
CAP+
NC
GND
ADM8829
1
2
3
6
5
4
CAP
NC = NO CONNECT
PIN FUNCTION DESCRIPTIONS
Mnemonic
Function
CAP+
Positive Charge-Pump Capacitor Terminal.
GND
Power Supply Ground.
CAP
Negative Charge-Pump Capacitor Terminal.
OUT
Output, Negative Voltage.
SHDN
Shutdown Control Input. This input, when
high, is used to disable the charge pump
thereby reducing the power consumption.
IN
Positive Power Supply Input.
ADM8828/ADM8829
3
REV. A
Typical Performance Characteristics
SUPPLY VOLTAGE V
0.8
0
1
5.5
1.5
SUPPLY CURRENT mA
2
2.5
3
3.5
4
4.5
5
0.7
0.4
0.3
0.2
0.1
0.6
0.5
Figure 2. Power Supply Current vs. Voltage
SUPPLY VOLTAGE V
35
0
1.5
5.5
2
OUTPUT RESISTANCE
2.5
3
3.5
4
4.5
5
30
20
15
10
5
25
Figure 3. Output Source Resistance vs. Supply Voltage
CAPACITANCE F
20
18
0
0.47
3.3
1
OUTPUT CURRENT mA
2.2
8
6
4
2
12
10
16
14
OUTPUT CURRENT @ V
IN
= 4.75V
OUTPUT CURRENT @ V
IN
= 3.15V
OUTPUT CURRENT @ V
IN
= 1.9V
Figure 4. Output Current vs. Capacitance
CAPACITANCE F
60
50
0
0.47
3.3
1
OUTPUT VOLTAGE RIPPLE mV p-p
2.2
40
30
20
10
OUTPUT VOLTAGE RIPPLE
@ V
IN
= 4.75V
OUTPUT VOLTAGE RIPPLE
@ V
IN
= 3.15V
OUTPUT VOLTAGE RIPPLE
@ V
IN
= 1.9V
I
L
= 5mA
Figure 5. Output Voltage Ripple vs. Capacitance
CAPACITANCE F
350
300
0
0.47
3.3
1
OUTPUT VOLTAGE RIPPLE mV p-p
2.2
200
150
100
50
250
OUTPUT VOLTAGE RIPPLE
@ V
IN
= 1.9V, V
OUT
= 1.5V
OUTPUT VOLTAGE RIPPLE
@ V
IN
= 4.75V, V
OUT
= 4.0V
OUTPUT VOLTAGE RIPPLE
@ V
IN
= 3.15V, V
OUT
= 2.5V
Figure 6. Output Voltage Ripple vs. Capacitance
OUTPUT CURRENT mA
0
5
0
45
5
OUTPUT VOLTAGE V
10
15
20
25
30
35
40
0.5
2.5
3.5
4
4.5
1
1.5
3
2
OUTPUT VOLTAGE @ V
IN
= 2.0V
OUTPUT VOLTAGE @ V
IN
= 3.3V
OUTPUT VOLTAGE @ V
IN
= 5.0V
Figure 7. Output Voltage vs. Output Current
ADM8828/ADM8829
4
REV. A
I
OUT
mA
100
40
0
0
50
5
P
EFF
%
10
15
20
25
30
35
40
45
90
50
30
10
70
60
20
80
P
EFF
@ V
IN
= 2.0V
P
EFF
@ V
IN
= 3.3V
P
EFF
@ V
IN
= 5.0V
Figure 8. Power Efficiency vs. Output Current
TEMPERATURE C
20
0
50
125
30
OUTPUT RESISTANCE
10
10
25
40
60
80
90
110
45
25
15
5
35
30
10
40
50
RESISTANCE ( ) @ V
IN
= 1.5V
RESISTANCE ( ) @ V
IN
= 3.3V
RESISTANCE ( ) @ V
IN
= 5.0V
Figure 9. Output Resistance vs. Temperature
TEMPERATURE C
200
80
0
50
125
30
PUMP FREQUENCY kHz
10
10
25
40
60
80
90
110
180
100
60
20
140
120
40
160
PUMP FREQUENCY
@ V
IN
= 5.0V
PUMP FREQUENCY
@ V
IN
= 3.3V
PUMP FREQUENCY
@ V
IN
= 1.5V
Figure 10. Charge Pump Frequency vs. Temperature
ADM8828/ADM8829
5
REV. A
GENERAL INFORMATION
The ADM8828/ADM8829 is a switched capacitor voltage con-
verter that can be used to invert the input supply voltage.
The voltage conversion task is achieved using a switched capaci-
tor technique using two external charge storage capacitors. An
on-chip oscillator and switching network transfers charge between
the charge storage capacitors. The basic principle behind the
voltage conversion scheme is illustrated below.
S1
S2
S3
S4
+
+
CAP+
CAP
C2
V+
OUT = V+
2
OSCILLATOR
1
2
C1
Figure 11. Voltage Inversion Principle
An oscillator generating antiphase signals
1 and
2 controls
switches S1, S2 and S3, S4. During
1, switches S1 and S2 are
closed while S3 and S4 are open, thereby charging C1 up to the
voltage at V+. During
2, S1 and S2 open and S3 and S4 close.
The positive terminal of C1 is connected to GND via S3 during
this phase and the negative terminal of C1 connects to V
OUT
via S4. The net result is voltage inversion at V
OUT
wrt GND.
Charge on C1 is transferred to C2 during
2. Capacitor C2
maintains this voltage during
1. The charge transfer efficiency
depends on the on-resistance of the switches, the frequency at
which they are being switched and also on the equivalent series
resistance (ESR) of the external capacitors. For maximum effi-
ciency, capacitors with low ESR are, therefore, recommended.
Shutdown Input
The ADM8828 contains a shutdown input that can be used to
disable the device and hence reduce the power consumption. A
logic high level on the SHDN input shuts the device down
reducing the quiescent current to 0.02
µ
A. During shutdown
the output voltage discharges to 0 V. Therefore, ground ref-
erenced loads are not powered during this state. When exiting
shutdown, it takes several cycles (approximately 175
µ
s) for the
charge pump to reach its final value. If the shutdown function is
not being used, SHDN should be hardwired to GND.
Capacitor Selection
The flying capacitor C1 can be increased to reduce the output
resistance.
The output capacitor size C2 affects the output ripple. Increas-
ing the capacitor size reduces the peak-peak ripple. The ESR
affects both the output impedance and the output ripple.
Reducing the ESR reduces the output impedance and ripple.
For convenience it is recommended that both C1 and C2 be the
same value.
The ac impedance of the ADM8828/ADM8829 may be reduced
by using a bypass capacitor on the input supply. This capacitor
should be connected between the input supply and GND. It will
provide instantaneous current surges as required. Suitable capaci-
tors of 1
µ
F or greater may be used.
+
+
+1.5V TO +5.5V
INPUT
SHUTDOWN
CONTROL
C1
1 F
C2
1 F
INVERTED
NEGATIVE
OUTPUT
ADM8828/
ADM8829
CAP+
CAP
GND
IN
SHDN
OUT
Figure 12. Typical Circuit Configuration
ADM8828/ADM8829
6
REV. A
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
C3352a010/99
PRINTED IN U.S.A.
6-Lead SOT-23
(RT-6)
0.122 (3.10)
0.106 (2.70)
PIN 1
0.118 (3.00)
0.098 (2.50)
0.075 (1.90)
BSC
0.037 (0.95) BSC
1
3
4
5
6
2
0.071 (1.80)
0.059 (1.50)
0.009 (0.23)
0.003 (0.08)
0.022 (0.55)
0.014 (0.35)
10
0
0.020 (0.50)
0.010 (0.25)
0.006 (0.15)
0.000 (0.00)
0.051 (1.30)
0.035 (0.90)
SEATING
PLANE
0.057 (1.45)
0.035 (0.90)
PDF 
ZIP