AD ADM8829ART Switched-capacitor voltage inverter with shutdown Datasheet

a
FEATURES
Inverts Input Supply Voltage
99% Voltage Conversion Efficiency
25 mA Output Current
Shutdown Function
Requires Only Two Capacitors
1 mF Capacitors
18 V Output Resistance
+1.5 V to +5.5 V Input Range
600 mA Quiescent Current
20 nA Shutdown Current (ADM8828)
Switched-Capacitor
Voltage Inverter with Shutdown
ADM8828/ADM8829
FUNCTIONAL BLOCK DIAGRAMS
OUT 1
IN 2
6 CAP+
ADM8828
5 SHDN
TOP VIEW
(Not to Scale) 4
CAP– 3
GND
OUT 1
IN 2
6 CAP+
ADM8829
5 NC
TOP VIEW
(Not to Scale) 4
CAP– 3
GND
APPLICATIONS
Handheld Instruments
LCD Panels
Cellular Phones
PDAs
Remote Data Acquisition
Op Amp Power Supplies
NC = NO CONNECT
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 quiescent current to 20 nA.
+1.5V TO +5.5V
INPUT
CAP+
C1 +
1mF
IN
ADM8828/
ADM8829
CAP–
GND
SHDN
SHUTDOWN
CONTROL
OUT
C2
+ 1mF
INVERTED
NEGATIVE
OUTPUT
Figure 1. Typical Circuit Configuration
The ADM8828/ADM8829 is available in a 6-lead SOT-23
package.
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.
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
ADM8828/ADM8829–SPECIFICATIONS
Parameter
Min
Input Voltage, IN
1.5
Supply Current
Output Current
Output Resistance
Output Ripple
25
Charge-Pump Frequency
50
65
Power Efficiency
Voltage Conversion Efficiency
99.5
Shutdown Supply Current, ISHDN
Shutdown Input Voltage, VSHDN
2.0
Typ
(VIN = +5 V, C1, C2 = 1 mF,1 TA = TMIN to TMAX unless otherwise noted)
Max
Units
Test Conditions/Comments
5.5
V
RL = 10 kΩ
600
1000
µA
Unloaded
18
25
130
28
mA
Ω
mV p-p
mV p-p
IL = 5 mA
IL = 5 mA
IL = 25 mA
120
190
kHz
kHz
VIN = +2.25 V
%
%
%
%
%
RL = 200 Ω
RL = 1 kΩ
No Load
RL = 1 kΩ
RL = 200 Ω
µA
V
V
µs
SHDN = IN
SHDN High = Disabled
SHDN Low = Enabled
IL = 5 mA
90
87
99.96
98
91
0.02
2
0.8
Shutdown Exit Time
175
NOTES
1
C1 and C2 are low ESR (<0.2 Ω) electrolytic capacitors. High ESR will degrade performance.
Specifications subject to change without notice.
PIN FUNCTION DESCRIPTIONS
ABSOLUTE MAXIMUM RATINGS*
(TA = +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)
θJA, 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.
Mnemonic
Function
CAP+
GND
CAP–
OUT
SHDN
Positive Charge-Pump Capacitor Terminal.
Power Supply Ground.
Negative Charge-Pump Capacitor Terminal.
Output, Negative Voltage.
Shutdown Control Input. This input, when
high, is used to disable the charge pump
thereby reducing the power consumption.
Positive Power Supply Input.
IN
PIN CONFIGURATIONS
OUT 1
6 CAP+
ADM8828
5 SHDN
IN 2
TOP VIEW
(Not to Scale) 4
CAP– 3
GND
ORDERING GUIDE
Model
Temperature
Range
Branding
Information
Package
Option*
ADM8828ART
ADM8829ART
–40°C to +85°C
–40°C to +85°C
MM0
MN0
RT-6
RT-6
OUT 1
IN 2
6 CAP+
ADM8829
5 NC
TOP VIEW
(Not to Scale) 4
CAP– 3
GND
NC = NO CONNECT
*RT-6 = 6-lead SOT-23.
–2–
REV. A
Typical Performance Characteristics– ADM8828/ADM8829
60
0.8
IL = 5mA
OUTPUT VOLTAGE RIPPLE – mV p-p
SUPPLY CURRENT – mA
0.7
0.6
0.5
0.4
0.3
0.2
50
OUTPUT VOLTAGE RIPPLE
@ VIN = 4.75V
40
OUTPUT VOLTAGE RIPPLE
@ VIN = 1.9V
30
20
OUTPUT VOLTAGE RIPPLE
@ VIN = 3.15V
10
0.1
0
1
1.5
2
2.5
3
3.5
4
SUPPLY VOLTAGE – V
4.5
5
0
0.47
5.5
Figure 2. Power Supply Current vs. Voltage
350
OUTPUT VOLTAGE RIPPLE – mV p-p
OUTPUT RESISTANCE – V
30
25
20
15
10
5
2
2.5
3
3.5
4
SUPPLY VOLTAGE – V
4.5
5
5.5
150
100
50
3.3
OUTPUT VOLTAGE @ VIN = 2.0V
–1
OUTPUT VOLTAGE – V
OUTPUT CURRENT – mA
OUTPUT VOLTAGE RIPPLE
@ VIN = 3.15V, VOUT = –2.5V
200
–0.5
OUTPUT CURRENT @ VIN = 4.75V
14
OUTPUT CURRENT @ VIN = 3.15V
10
8
OUTPUT CURRENT @ VIN = 1.9V
–1.5
–2
OUTPUT VOLTAGE @ VIN = 3.3V
–2.5
–3
–3.5
4
–4
2
–4.5
0
0.47
2.2
1
CAPACITANCE – mF
–5
3.3
Figure 4. Output Current vs. Capacitance
REV. A
250
0
16
6
OUTPUT VOLTAGE RIPPLE
@ VIN = 4.75V, VOUT = –4.0V
Figure 6. Output Voltage Ripple vs. Capacitance
20
12
300
OUTPUT VOLTAGE RIPPLE
@ VIN = 1.9V, VOUT = –1.5V
0
2.2
0.47
1
CAPACITANCE – mF
Figure 3. Output Source Resistance vs. Supply Voltage
18
3.3
Figure 5. Output Voltage Ripple vs. Capacitance
35
0
1.5
1
2.2
CAPACITANCE – mF
OUTPUT VOLTAGE @ VIN = 5.0V
0
5
10
15
20
25
30
OUTPUT CURRENT – mA
35
40
Figure 7. Output Voltage vs. Output Current
–3–
45
ADM8828/ADM8829
100
200
PEFF @ VIN = 5.0V
180
80
160
PEFF – %
70
PUMP FREQUENCY – kHz
90
PEFF @ VIN = 3.3V
60
PEFF @ VIN = 2.0V
50
40
30
100
60
10
20
5
10
15
20
25
30
IOUT – mA
35
40
45
0
–50
50
Figure 8. Power Efficiency vs. Output Current
PUMP FREQUENCY
@ VIN = 1.5V
80
40
0
PUMP FREQUENCY
@ VIN = 5.0V
120
20
0
PUMP FREQUENCY
@ VIN = 3.3V
140
–30
–10
10
25
40
60
80
TEMPERATURE – 8C
90
110
125
Figure 10. Charge Pump Frequency vs. Temperature
50
45
RESISTANCE (V) @ VIN = 1.5V
OUTPUT RESISTANCE – V
40
35
30
RESISTANCE (V) @ VIN = 3.3V
25
20
RESISTANCE (V) @ VIN = 5.0V
15
10
5
0
–50
–30
–10
10
25
40
60
80
TEMPERATURE – 8C
90
110
125
Figure 9. Output Resistance vs. Temperature
–4–
REV. A
ADM8828/ADM8829
GENERAL INFORMATION
Capacitor Selection
The ADM8828/ADM8829 is a switched capacitor voltage converter that can be used to invert the input supply voltage.
The flying capacitor C1 can be increased to reduce the output
resistance.
The voltage conversion task is achieved using a switched capacitor 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.
The output capacitor size C2 affects the output ripple. Increasing the capacitor size reduces the peak-peak ripple. The ESR
affects both the output impedance and the output ripple.
V+
CAP+
S1
Reducing the ESR reduces the output impedance and ripple.
For convenience it is recommended that both C1 and C2 be the
same value.
S3
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 capacitors of 1 µF or greater may be used.
+
C1
S2
S4
+
CAP–
F1
42
OSCILLATOR
OUT = –V+
C2
F2
Figure 11. Voltage Inversion Principle
+1.5V TO +5.5V
INPUT
An oscillator generating antiphase signals φ1 and φ2 controls
switches S1, S2 and S3, S4. During φ1, switches S1 and S2 are
closed while S3 and S4 are open, thereby charging C1 up to the
voltage at V+. During φ2, 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 VOUT
via S4. The net result is voltage inversion at VOUT wrt GND.
Charge on C1 is transferred to C2 during φ2. Capacitor C2
maintains this voltage during φ1. 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 efficiency, capacitors with low ESR are, therefore, recommended.
CAP+
C1 +
1mF
CAP–
GND
SHDN
SHUTDOWN
CONTROL
OUT
C2
+ 1mF
INVERTED
NEGATIVE
OUTPUT
Figure 12. Typical Circuit Configuration
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 µA. During shutdown
the output voltage discharges to 0 V. Therefore, ground referenced loads are not powered during this state. When exiting
shutdown, it takes several cycles (approximately 175 µs) for the
charge pump to reach its final value. If the shutdown function is
not being used, SHDN should be hardwired to GND.
REV. A
IN
ADM8828/
ADM8829
–5–
ADM8828/ADM8829
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
6-Lead SOT-23
(RT-6)
0.071 (1.80)
0.059 (1.50)
6
5
4
1
2
3
C3352a–0–10/99
0.122 (3.10)
0.106 (2.70)
0.118 (3.00)
0.098 (2.50)
PIN 1
0.037 (0.95) BSC
0.075 (1.90)
BSC
0.006 (0.15)
0.000 (0.00)
0.057 (1.45)
0.035 (0.90)
0.020 (0.50) SEATING
0.010 (0.25) PLANE
108
0.009 (0.23) 08
0.003 (0.08)
0.022 (0.55)
0.014 (0.35)
PRINTED IN U.S.A.
0.051 (1.30)
0.035 (0.90)
–6–
REV. A
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