_______________General Description
The ultra-small MAX828/MAX829 monolithic, CMOS
charge-pump inverters accept input voltages ranging
from +1.5V to +5.5V. The MAX828 operates at 12kHz,
and the MAX829 operates at 35kHz. Their high efficiency
(greater than 90% over most of the load-current range)
and low operating current (60A for the MAX828) make
these devices ideal for both battery-powered and board-
level voltage-conversion applications.
The MAX828/MAX829 combine low quiescent current
and high efficiency. Oscillator control circuitry and four
power MOSFET switches are included on-chip.
Applications include generating a -5V supply from a +5V
logic supply to power analog circuitry. Both parts come
in a 5-pin SOT23-5 package and can deliver 25mA with
a voltage drop of 500mV.
For applications requiring more power, the MAX860
delivers up to 50mA with a voltage drop of 600mV, in a
space-saving MAX package.
________________________Applications
Small LCD Panels
Cell Phones
Medical Instruments
Handy-Terminals, PDAs
Battery-Operated Equipment
____________________________Features
o
5-Pin SOT23-5 Package
o
95% Voltage Conversion Efficiency
o
Inverts Input Supply Voltage
o
60A Quiescent Current (MAX828)
o
+1.5V to +5.5V Input Voltage Range
o
Requires Only Two Capacitors
o
25mA Output Current
MAX828/MAX829
Switched-Capacitor Voltage Inverters
________________________________________________________________
Maxim Integrated Products
1
TOP VIEW
IN
GND
C1-
C1+
OUT
SOT23-5
1
5
MAX828
MAX829
2
3
4
__________________Pin Configuration
NEGATIVE VOLTAGE CONVERTER
C1+
C1-
IN
OUT
GND
INPUT
SUPPLY
VOLTAGE
NEGATIVE
OUTPUT
VOLTAGE
MAX828
MAX829
4
3
5
2
1
__________Typical Operating Circuit
19-0495; Rev 2; 4/97
PART
MAX828
C/D
MAX828EUK
-40C to +85C
0C to +70C
TEMP. RANGE
PIN-
PACKAGE
Dice*
5 SOT23-5
______________Ordering Information
*
Dice are tested at T
A
= +25C.
MAX829
C/D
MAX829EUK
-40C to +85C
0C to +70C
Dice*
5 SOT23-5
SOT
TOP MARK
--
AABI
--
AABJ
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAX828/MAX829
Switched-Capacitor Voltage Inverters
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
IN
= +5V, C1 = C2 = 10F (MAX828), C1 = C2 = 3.3F (MAX829), T
A
= 0C to +85C, unless otherwise noted. Typical values
are at T
A
= +25C.)
ELECTRICAL CHARACTERISTICS
(V
IN
= +5V, C1 = C2 = 10F (MAX828), C1 = C2 = 3.3F (MAX829), T
A
= -40C to +85C, unless otherwise noted. Typical values
are at T
A
= +25C.) (Note 2)
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Note 1:
Capacitor contribution is approximately 20% of the output impedance [ESR + 1 / (pump frequency x capacitance)].
Note 2:
All -40C to +85C specifications above are guaranteed by design.
IN to GND .................................................................+6.0V, -0.3V
OUT to GND .............................................................-6.0V, +0.3V
OUT Output Current ...........................................................50mA
OUT Short-Circuit to GND ............................................Indefinite
Continuous Power Dissipation (T
A
= +70C)
SOT23-5 (derate 7.1mW/C above +70C)...................571mW
Operating Temperature Range
MAX828EUK/MAX829EUK ...............................-40C to +85C
Storage Temperature Range .............................-65C to +160C
Lead Temperature (soldering, 10sec) .............................+300C
MAX829
MAX828
R
LOAD
=
R
LOAD
= 10k
, T
A
= +25C
MAX829
R
LOAD
= 10k
R
LOAD
= 10k
MAX828
CONDITIONS
A
150
260
60
90
Supply Current
%
95
99.9
Voltage Conversion Efficiency
%
98
Power Efficiency
kHz
24.5
35
45.5
Oscillator Frequency
1.25
1.0
V
1.5
Minimum Supply Voltage
V
5.5
Maximum Supply Voltage
8.4
12
15.6
UNITS
MIN
TYP
MAX
PARAMETER
T
A
= +25C
T
A
= 0C to + 85C
I
OUT
= 5mA
T
A
= 0C to + 85C
T
A
= +25C
65
Output Resistance
20
50
MAX829
MAX828
I
OUT
= 5mA
MAX829
R
LOAD
= 10k
MAX828
CONDITIONS
A
325
115
Supply Current
65
Output Resistance
kHz
19
54.3
Oscillator Frequency
V
1.5
5.5
Supply Voltage Range
6
20
UNITS
MIN
TYP
MAX
PARAMETER
T
A
= +25C
T
A
= +25C
MAX828/MAX829
Switched-Capacitor Voltage Inverters
_______________________________________________________________________________________
3
40
0
1.5
2.5
OUTPUT RESISTANCE
vs. SUPPLY VOLTAGE
5
10
35
MAX828/829-01
SUPPLY VOLTAGE (V)
OUTPUT RESISTANCE (
)
3.5
5.5
4.5
30
20
25
15
MAX829
MAX828
50
10
OUTPUT RESISTANCE
vs. TEMPERATURE
15
40
45
MAX828/829-02
TEMPERATURE (C)
OUTPUT RESISTANCE (
)
35
30
25
20
V
IN
= 3.3V
V
IN
= 5.0V
V
IN
= 1.5V
-40
-20
0
60
20
40
80
45
0
0
10
5
15
35 40
MAX828
OUTPUT CURRENT vs. CAPACITANCE
5
35
40
MAX828/829-03
CAPACITANCE (
F)
OUTPUT CURRENT (mA)
20 25 30
45 50
30
25
20
15
10
V
IN
= 3.15V, V
OUT
= -2.5V
V
IN
= 1.9V, V
OUT
= -1.5V
V
IN
= 4.75V, V
OUT
= -4.0V
45
0
0
5
20
25
MAX829
OUTPUT CURRENT vs. CAPACITANCE
5
35
40
MAX828/829-04
CAPACITANCE (
F)
OUTPUT CURRENT (mA)
15
10
30
30
25
20
15
10
V
IN
= 3.15V, V- = -2.5V
V
IN
= 1.9V, V- = -1.5V
V
IN
= 4.75V, V- = -4.0V
200
0
1.5
2.5
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
25
50
175
MAX828/829-07
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
A)
3.5
5.5
4.5
150
100
125
75
MAX829
MAX828
500
450
0
0
5
20
25
MAX828
OUTPUT VOLTAGE RIPPLE
vs. CAPACITANCE
50
350
400
MAX828/829-05
CAPACITANCE (
F)
OUTPUT VOLTAGE RIPPLE (mVp-p)
15
10
30
300
250
200
150
100
V
IN
= 4.75V, V
OUT
= -4.0V
V
IN
= 3.15V, V
OUT
= -2.5V
V
IN
= 1.9V, V
OUT
= -1.5V
450
0
0
5
20
25
MAX829
OUTPUT VOLTAGE RIPPLE
vs. CAPACITANCE
50
350
400
MAX828/829-06
CAPACITANCE (
F)
OUTPUT VOLTAGE RIPPLE (mVp-p)
15
10
30
300
250
200
150
100
V
IN
= 4.75V, V
OUT
= -4.0V
V
IN
= 3.15V, V
OUT
= -2.5V
V
IN
= 1.9V, V
OUT
= -1.5V
60
55
45
35
25
15
10
-40
-20
0
60
MAX828
PUMP FREQUENCY vs. TEMPERATURE
20
50
MAX828/829-08
TEMPERATURE (C)
PUMP FREQUENCY (kHz)
20
40
80
40
30
V
IN
= 3.3V
V
IN
= 5.0V
V
IN
= 1.5V
__________________________________________Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= +5V, C1 = C2 = C3, T
A
= +25C, unless otherwise noted.)
55
30
MAX829
PUMP FREQUENCY vs. TEMPERATURE
35
50
MAX828/829-9
TEMPERATURE (C)
PUMP FREQUENCY (kHz)
45
40
V
IN
= 3.3V
V
IN
= 5.0V
V
IN
= 1.5V
-40
-20
0
60
20
40
80
_____________________Pin Description
MAX828/MAX829
Switched-Capacitor Voltage Inverters
4
_______________________________________________________________________________________
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
IN
= +5V, C1 = C2 = C3, T
A
= +25C, unless otherwise noted.)
0.5
-5.5
0
5
15
10
35
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
-4.5
-0.5
MAX828/829-10
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
20
30
25
45 50
40
-1.5
-2.5
-3.5
V
IN
= 3.3V
V
IN
= 5.0V
V
IN
= 2.0V
100
0
0
5
10
EFFICIENCY vs. OUTPUT CURRENT
10
30
20
90
MAX828/829-11
OUTPUT CURRENT (mA)
EFFICIENCY (
%
)
20
15
30
25
45
40
50
35
70
80
50
60
40
V
IN
= 2.0V
V
IN
= 3.3V
V
IN
= 5.0V
V
OUT
20mV/div
MAX828
OUTPUT NOISE AND RIPPLE
MAX828/829-12
V
IN
= 3.3V, V
OUT
= -3.2V, I
OUT
= 5mA, AC COUPLED
20
s/div
Flying Capacitor's Positive Terminal
C1+
5
Ground
GND
4
Flying Capacitor's Negative Terminal
C1-
3
PIN
Positive Power-Supply Input
IN
2
Inverting Charge-Pump Output
OUT
1
FUNCTION
NAME
VOLTAGE INVERTER
OUT
IN
C1+
V
IN
R
L
C1
3.3
F*
*10
F
(MAX828)
C2
3.3
F*
C3
3.3
F*
5
1
2
3
4
V
OUT
GND
C1-
MAX828
MAX829
Figure 1. Test Circuit
V
OUT
20mV/div
MAX829
OUTPUT NOISE AND RIPPLE
MAX828/829-13
V
IN
= 3.3V, V
OUT
= -3.2V, I
OUT
= 5mA, AC COUPLED
10
s/div
_______________Detailed Description
The MAX828/MAX829 capacitive charge pumps invert the
voltage applied to their input. For highest performance,
use low equivalent series resistance (ESR) capacitors.
During the first half-cycle, switches S2 and S4 open,
switches S1 and S3 close, and capacitor C1 charges to
the voltage at IN (Figure 2). During the second half-
cycle, S1 and S3 open, S2 and S4 close, and C1 is level
shifted downward by V
IN
volts. This connects C1 in par-
allel with the reservoir capacitor C2. If the voltage across
C2 is smaller than the voltage across C1, then charge
flows from C1 to C2 until the voltage across C2 reaches -
V
IN
. The actual voltage at the output is more positive
than -V
IN
, since switches S1S4 have resistance and the
load drains charge from C2.
Charge-Pump Output
The MAX828/MAX829 are not voltage regulators: the
charge pump's output source resistance is approxi-
mately 20
at room temperature (with V
IN
= +5V), and
V
OUT
approaches -5V when lightly loaded. V
OUT
will
droop toward GND as load current increases. The
droop of the negative supply (V
DROOP-
) equals the cur-
rent draw from OUT (I
OUT
) times the negative convert-
er's source resistance (RS-):
V
DROOP-
= I
OUT
x RS-
The negative output voltage will be:
V
OUT
= -(V
IN
- V
DROOP-
)
Efficiency Considerations
The power efficiency of a switched-capacitor voltage
converter is affected by three factors: the internal loss-
es in the converter IC, the resistive losses of the pump
capacitors, and the conversion losses during charge
transfer between the capacitors. The total power loss is:
The internal losses are associated with the IC's internal
functions, such as driving the switches, oscillator, etc.
These losses are affected by operating conditions such
as input voltage, temperature, and frequency.
The next two losses are associated with the voltage
converter circuit's output resistance. Switch losses
occur because of the on-resistance of the MOSFET
switches in the IC. Charge-pump capacitor losses
occur because of their ESR. The relationship between
these losses and the output resistance is as follows:
where f
OSC
is the oscillator frequency. The first term is
the effective resistance from an ideal switched-
capacitor circuit. See Figures 3a and 3b.
P
= P
+ P
+ P
+ P
LOSS
INTERNAL LOSSES
SWITCH LOSSES
PUMP CAPACITOR LOSSES
CONVERSION LOSSES
MAX828/MAX829
Switched-Capacitor Voltage Inverters
_______________________________________________________________________________________
5
S1
IN
S2
S3
S4
C1
C2
V
OUT
= -(V
IN
)
Figure 2. Ideal Voltage Inverter
V+
C1
f
C2
R
L
V
OUT
Figure 3a. Switched-Capacitor Model
R
EQUIV
=
R
EQUIV
V
OUT
R
L
1
V+
f
C1
C2
Figure 3b. Equivalent Circuit
P
+ P
= I
x R
PUMP CAPACITOR LOSSES
CONVERSION LOSSES
OUT
2
OUT
R
f
x C
R
ESR
ESR
OUT
OSC
SWITCHES
C
C
( )
+
+
(
)
+
1
1
4 2
1
2
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