MAX870C/D [MAXIM]
Switched-Capacitor Voltage Inverters; 开关电容电压逆变器
| 型号： | MAX870C/D |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Switched-Capacitor Voltage Inverters |
| 文件： | 总8页 (文件大小：100K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1240; Rev 0; 6/97
S w it c h e d -Ca p a c it o r Vo lt a g e In ve rt e rs
0/MAX871
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ 5-Pin SOT23-5 Package
The ultra-small MAX870/MAX871 monolithic, CMOS
charge-pump inverters accept input voltages ranging
from +1.4V to +5.5V. The MAX870 operates at 125kHz,
and the MAX871 operates at 500kHz. Their high efficien-
c y (90%) a nd low op e ra ting c urre nt (0.7mA for the
MAX870) make these devices ideal for both battery-pow-
ered and board-level voltage-conversion applications.
♦ 99% Voltage Conversion Efficiency
♦ Invert Input Supply Voltage
♦ 0.7mA Quiescent Current (MAX870)
♦ +1.4V to +5.5V Input Voltage Range
♦ Require Only Two Capacitors
♦ 25mA Output Current
Oscillator control circuitry and four power MOSFET
s witc he s a re inc lud e d on-c hip . A typ ic a l MAX870/
MAX871 application is 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.
♦ Shutdown Control
For applications requiring more power, the MAX860
delivers up to 50mA with a voltage drop of 600mV, in a
space-saving µMAX package.
______________Ord e rin g In fo rm a t io n
PIN-
SOT
PART
TEMP. RANGE
PACKAGE TOP MARK
________________________Ap p lic a t io n s
Local -5V Supply from 5V Logic Supply
Small LCD Panels
MAX870C/D
0°C to +70°C
Dice*
—
MAX870EUK -40°C to +85°C
MAX871C/D 0°C to +70°C
MAX871EUK -40°C to +85°C
* Dice are tested at T = +25°C.
5 SOT23-5
Dice*
ABZN
—
5 SOT23-5
ABZO
Cell Phones
A
Medical Instruments
Handy-Terminals, PDAs
Battery-Operated Equipment
__________________P in Co n fig u ra t io n
__________Typ ic a l Op e ra t in g Circ u it
TOP VIEW
INPUT
SUPPLY
VOLTAGE
5
2
IN
C1+
MAX870
MAX871
OUT
IN
1
2
3
C1+
5
4
MAX870
MAX871
3
4
C1-
NEGATIVE
OUTPUT
VOLTAGE
1
OUT
C1-
GND
GND
SOT23-5
NEGATIVE VOLTAGE CONVERTER
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
S w it c h e d -Ca p a c it o r Vo lt a g e In ve rt e rs
ABSOLUTE MAXIMUM RATINGS
IN to GND..............................................................+6.0V to -0.3V
OUT to GND ..........................................................-6.0V to +0.3V
Continuous Power Dissipation (T = +70°C)
A
SOT23-5 (derate 7.1mW/°C above +70°C)...................571mW
Operating Temperature Range
C1+ ..............................................................(V + 0.3V) to -0.3V
IN
C1-............................................................(V
OUT Output Current ...........................................................50mA
OUT Short Circuit to GND .............................................Indefinite
- 0.3V) to +0.3V
MAX870EUK/MAX871EUK ...............................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
OUT
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.
ELECTRICAL CHARACTERISTICS
(V = +5V, C1 = C2 = 1µF (MAX870), C1 = C2 = 0.33µF (MAX871), T = 0°C to +85°C, unless otherwise noted. Typical values
IN
A
are at T = +25°C.)
A
PARAMETER
CONDITIONS
MIN
TYP
0.7
MAX
1.0
UNITS
MAX870
MAX871
Supply Current
T
A
= +25°C
mA
8
2.7
3.8
T
= +25°C
1.4
1.5
1.0
A
Minimum Supply Voltage
Maximum Supply Voltage
Oscillator Frequency
R
R
= 10kΩ
V
V
LOAD
LOAD
T
A
= 0°C to + 85°C
= 10kΩ
5.5
169
675
MAX870
MAX871
MAX870
MAX871
MAX870
MAX871
81
125
500
90
T
A
= +25°C
kHz
325
R
LOAD
= 500kΩ,
Power Efficiency
%
%
T =+25°C
A
75
98
96
99.3
99
R
= ∞, T =+25°C
Voltage Conversion Efficiency
LOAD
A
C1 = C2 = 1µF
20
50
50
MAX870
MAX871
C1 = C2 = 0.47µF
C1 = C2 = 0.33µF
C1 = C2 = 0.22µF
C1 = C2 = 0.1µF
25
T
=
= +25°C
20
A
I
OUT
Output Resistance (Note 1)
Ω
5mA
25
35
T
A
= 0°C to + 85°C
65
Note 1: Capacitor contribution is approximately 20% of the output impedance [ESR + 1 / (pump frequency x capacitance)].
ELECTRICAL CHARACTERISTICS
(V = +5V, C1 = C2 = 1µF (MAX870), C1 = C2 = 0.33µF (MAX871), T = -40°C to +85°C, unless otherwise noted.) (Note 2)
IN
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
1.3
UNITS
MAX870
MAX871
Supply Current
mA
4.4
Minimum Supply-Voltage Range
Maximum Supply-Voltage Range
R
R
= 10kΩ
= 10kΩ
1.6
V
V
LOAD
LOAD
5.5
194
775
65
MAX870
MAX871
56
Oscillator Frequency
kHz
Ω
225
Output Resistance
I
= 5mA
OUT
MAX870
MAX871
97
95
R
= ∞
Voltage Conversion Efficiency
%
LOAD
Note 2: All -40°C to +85°C specifications are guaranteed by design.
2
_______________________________________________________________________________________
S w it c h e d -Ca p a c it o r Vo lt a g e In ve rt e rs
0/MAX871
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(Circuit of Figure 1, V = +5V, C1 = C2 = C3, T = +25°C, unless otherwise noted.)
IN
A
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
OUTPUT RESISTANCE
vs. SUPPLY VOLTAGE
MAX870
OUTPUT RESISTANCE vs. TEMPERATURE
50
45
40
35
30
25
20
15
10
5
3.0
2.5
2.0
1.5
1.0
0.5
0
60
50
40
30
20
10
V
IN
= 1.5V
V
IN
= 3.3V
MAX871
MAX871
MAX870
V
= 5.0V
IN
MAX870
0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
-40
-15
10
35
60
85
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
MAX870
MAX871
MAX870
OUTPUT VOLTAGE RIPPLE
vs. CAPACITANCE
OUTPUT RESISTANCE vs. TEMPERATURE
OUTPUT CURRENT vs. CAPACITANCE
450
400
350
300
250
200
150
100
50
70
60
50
40
30
20
10
0
45
40
35
30
25
20
15
10
5
V
IN
= 4.75V, V = -4.0V
OUT
V = 4.75V, V = -4.0V
IN OUT
V
IN
= 3.15V, V = -2.5V
OUT
V
= 1.5V
IN
V
IN
= 1.9V, V = -1.5V
OUT
V
IN
= 3.15V, V = -2.5V
OUT
V
IN
= 3.3V
= 5.0V
V
IN
= 1.9V, V = -1.5V
OUT
V
IN
0
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
-40
-15
10
35
60
85
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5
CAPACITANCE (µF)
TEMPERATURE (°C)
CAPACITANCE (µF)
MAX870
MAX871
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX871
OUTPUT VOLTAGE RIPPLE
vs. CAPACITANCE
OUTPUT CURRENT vs. CAPACITANCE
0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
-4.0
-4.5
-5.0
500
35
30
25
20
15
10
5
V
= 4.75V, V = -4.0V
OUT
IN
450
400
350
300
250
200
150
100
50
V = 2.0V
IN
V
IN
= 4.75V, V = -4.0V
OUT
V
= 3.15V, V = -2.5V
OUT
IN
V = 3.3V
IN
V
IN
= 3.15V, V = -2.5V
OUT
V
IN
= 1.9V, V = -1.5V
OUT
V
= 1.9V, V = -1.5V
OUT
IN
V = 5.0V
IN
0
0
0
5
10 15 20 25 30 35 40 45
OUTPUT CURRENT (mA)
0
0.5
1.0
1.5
2.0
2.5
0
0.5
1.0
1.5
2.0
2.5
CAPACITANCE (µF)
CAPACITANCE (µF)
_______________________________________________________________________________________
3
S w it c h e d -Ca p a c it o r Vo lt a g e In ve rt e rs
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(Circuit of Figure 1, V = +5V, C1 = C2 = C3, T = +25°C, unless otherwise noted.)
IN
A
MAX870
MAX871
EFFICIENCY vs. OUTPUT CURRENT
EFFICIENCY vs. OUTPUT CURRENT
PUMP FREQUENCY vs. TEMPERATURE
100
90
80
70
60
50
40
30
20
10
0
600
550
500
450
400
350
300
250
200
150
100
90
80
70
60
50
40
30
20
10
0
V
IN
= 5.0V
V
IN
= 3.3V OR 5.0V, MAX871
V
IN
= 5.0V
V
IN
= 3.3V
V
IN
= 1.5V, MAX871
V
IN
= 2.0V
V
IN
= 3.3V
V
IN
= 2.0V
V
IN
= 1.5V, MAX870
V
IN
= 3.3V OR 5.0V, MAX870
0/MAX871
0
5
10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
0
5
10 15 20 25 30 35 40
OUTPUT CURRENT (mA)
-40
-15
10
35
60
85
TEMPERATURE (°C)
MAX870
MAX871
OUTPUT NOISE AND RIPPLE
OUTPUT NOISE AND RIPPLE
2µs/div
1µs/div
V
IN
= 3.3V, V
= -3.18V, I = 5mA,
V
IN
= 3.3V, V
= -3.14V, I = 5mA,
OUT
OUT
OUT OUT
20mV/div, AC COUPLED
20mV/div, AC COUPLED
_____________________P in De s c rip t io n
V
IN
C3
0.33µF*
R
L
PIN
1
NAME
OUT
IN
FUNCTION
V
OUT
Inverting Charge-Pump Output
Positive Power-Supply Input
Flying Capacitor’s Negative Terminal
Ground
1
5
C1+
OUT
IN
2
C2
0.33µF*
2
3
MAX870
MAX871
3
C1-
C1
0.33µF*
4
GND
C1+
4
C1-
GND
5
Flying Capacitor’s Positive Terminal
*1µF
(MAX870)
VOLTAGE INVERTER
Figure 1. Test Circuit
_______________________________________________________________________________________
4
S w it c h e d -Ca p a c it o r Vo lt a g e In ve rt e rs
0/MAX871
_______________De t a ile d De s c rip t io n
The MAX870/MAX871 capacitive charge pumps invert
the voltage applied to their input. For highest perfor-
mance, use low equivalent series resistance (ESR)
capacitors (e.g., ceramic).
S1
S2
IN
C1
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
C2
S3
S4
V
OUT
= -(V )
IN
shifted downward by V volts. This connects C1 in par-
IN
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 . The actual voltage at the output is more positive
IN
than -V , since switches S1–S4 have resistance and the
IN
load drains charge from C2.
Figure 2. Ideal Voltage Inverter
Ch a rg e -P u m p Ou t p u t
The MAX870/MAX871 are not voltage regulators: the
charge pump’s output source resistance is approxi-
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.
mately 20Ω at room temperature (with V = +5V), and
IN
V
OUT
approaches -5V when lightly loaded. V
will
OUT
d roop towa rd GND a s loa d c urre nt inc re a s e s . The
droop of the negative supply (V ) equals the cur-
DROOP-
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
s witc he s in the IC. Cha rg e -p ump c a p a c itor los s e s
occur because of their ESR. The relationship between
these losses and the output resistance is as follows:
rent draw from OUT (I ) times the negative convert-
OUT
er’s source resistance (RS-):
V
= I x RS-
OUT
DROOP-
The negative output voltage will be:
= -(V – V )
DROOP-
V
OUT
IN
P
+ P
PUMP CAPACITOR LOSSES
CONVERSION LOSSES
Effic ie n c y Co n s id e ra t io n s
2
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:
= I
x R
1
OUT
OUT
R
+2R
+ 4ESR +ESR
OUT
SWITCHES C1 C2
f
x C1
OSC
where f
is the oscillator frequency. The first term is
OSC
ΣP
= P
+ P
LOSS
INTERNAL LOSSES
SWITCH LOSSES
the e ffe c tive re s is ta nc e from a n id e a l s witc he d -
capacitor circuit. See Figures 3a and 3b.
+ P
PUMP CAPACITOR LOSSES
CONVERSION LOSSES
+ P
f
R
EQUIV
V+
V+
V
OUT
V
OUT
1
R
EQUIV
=
f × C1
C2
R
L
C1
C2
R
L
Figure 3b. Equivalent Circuit
_______________________________________________________________________________________
Figure 3a. Switched-Capacitor Model
5
S w it c h e d -Ca p a c it o r Vo lt a g e In ve rt e rs
Conversion losses occur during the charge transfer
between C1 and C2 when there is a voltage difference
between them. The power loss is:
noise. The recommended bypassing depends on the cir-
cuit configuration and on where the load is connected.
When the inverter is loaded from OUT to GND, current
from the supply switches between 2 x I
Therefore, use a large bypass capacitor (e.g., equal to
the value of C1) if the supply has a high AC impedance.
and zero.
OUT
2
IN
2
P
= [1/ C1
V
− V
+
CONV.LOSS
1/ C2
2
OUT
2
V
− 2V
V
] x f
2
RIPPLE
OUT RIPPLE OSC
When the inverter is loaded from IN to OUT, the circuit
draws 2 x I
constantly, except for short switching
OUT
spikes. A 0.1µF bypass capacitor is sufficient.
__________Ap p lic a t io n s In fo rm a t io n
Vo lt a g e In ve rt e r
Ca p a c it o r S e le c t io n
To maintain the lowest output resistance, use capaci-
tors with low ESR (Table 1). The charge-pump output
re s is ta nc e is a func tion of C1’s a nd C2’s ESR.
Therefore, minimizing the charge-pump capacitor’s
ESR minimizes the total output resistance.
The most common application for these devices is a
charge-pump voltage inverter (Figure 1). This applica-
tion requires only two external components—capacitors
C1 and C2—plus a bypass capacitor, if necessary.
Refer to the Capacitor Selection section for suggested
capacitor types.
0/MAX871
Flying Capacitor (C1)
Increasing the flying capacitor’s size reduces the out-
put resistance. Small C1 values increase the output
re s is ta nc e . Ab ove a c e rta in p oint, inc re a s ing C1’s
capacitance has a negligible effect, because the out-
p ut re s is ta nc e b e c ome s d omina te d b y the inte rna l
switch resistance and capacitor ESR.
Ca s c a d in g De vic e s
Two devices can be cascaded to produce an even
larger negative voltage (Figure 4). The unloaded output
voltage is normally -2 x V , but this is reduced slightly
IN
by the output resistance of the first device multiplied by
the quiescent current of the second. When cascading
more than two devices, the output resistance rises dra-
matically. For applications requiring larger negative
voltages, see the MAX864 and MAX865 data sheets.
Output Capacitor (C2)
Increasing the output capacitor’s size reduces the out-
put ripple voltage. Decreasing its ESR reduces both
output resistance and ripple. Smaller capacitance val-
ues can be used with light loads if higher output ripple
can be tolerated. Use the following equation to calcu-
late the peak-to-peak ripple:
P a ra lle lin g De vic e s
Paralleling multiple MAX870s or MAX871s reduces the
output resistance. Each device requires its own pump
capacitor (C1), but the reservoir capacitor (C2) serves
all devices (Figure 5). Increase C2’s value by a factor
of n, where n is the number of parallel devices. Figure 5
shows the equation for calculating output resistance.
I
OUT
x C2
V
=
+ 2 x I
x ESR
RIPPLE
OUT
C2
f
OSC
Co m b in e d Do u b le r/In ve rt e r
In the circuit of Figure 6, capacitors C1 and C2 form the
inverter, while C3 and C4 form the doubler. C1 and C3
are the pump capacitors; C2 and C4 are the reservoir
Input Bypass Capacitor
Bypass the incoming supply to reduce its AC impedance
and the impact of the MAX870/MAX871’s switching
Table 1. Low-ESR Capacitor Manufacturers
PRODUCTION
METHOD
MANUFACTURER
SERIES
PHONE
FAX
AVX
TPS series
267 series
593D, 595D series
X7R
(803) 946-0690
(714) 969-2491
(603) 224-1961
(803) 946-0690
(714) 969-2491
(803) 626-3123
(714) 960-6492
(603) 224-1430
(803) 626-3123
(714) 960-6492
Surface-Mount
Tantalum
Matsuo
Sprague
AVX
Surface-Mount
Ceramic
Matsuo
X7R
6
_______________________________________________________________________________________
S w it c h e d -Ca p a c it o r Vo lt a g e In ve rt e rs
0/MAX871
…
IN
…
+V
2
1
2
1
+V
IN
3
4
3
4
2
2
1
MAX870
MAX871
“1”
MAX870
MAX871
“n”
C1
3
4
5
3
4
5
C1
V
OUT
MAX870
MAX871
“1”
MAX870
MAX871
“n”
5
5
C1
C1
…
V
OUT
1
C2
C2
…
V
OUT
= -nV
IN
R
OF SINGLE DEVICE
C2
V
OUT
= -V
IN
OUT
R
OUT
=
NUMBER OF DEVICES
Figure 4. Cascading MAX870s or MAX871s to Increase
Output Voltage
Figure 5. Paralleling MAX870s or MAX871s to Reduce Output
Resistance
capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline toward GND. Make sure
the sum of the currents drawn from the two outputs
does not exceed 40mA.
+V
IN
D1, D2 = 1N4148
3
4
2
1
C1
MAX870
MAX871
D1
D2
He a vy Ou t p u t Cu rre n t Lo a d s
Under heavy loads, where higher supply is sourcing cur-
rent into OUT, the OUT supply must not be pulled above
ground. Applications that sink heavy current into OUT
require a Schottky diode (1N5817) between GND and
OUT, with the anode connected to OUT (Figure 7).
5
V
OUT
= -V
IN
C2
C4
V
= (2V ) -
IN
OUT
(V ) - (V
)
FD2
FD1
C3
La yo u t a n d Gro u n d in g
Good layout is important, primarily for good noise per-
formance. To ensure good layout, mount all compo-
nents as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
Figure 6. Combined Doubler and Inverter
4
GND
MAX870
MAX871
1
OUT
Figure 7. High V- Load Current
_______________________________________________________________________________________
7
S w it c h e d -Ca p a c it o r Vo lt a g e In ve rt e rs
S h u t d o w n Co n t ro l
If shutdown control is necessary, use the circuit in
Figure 8. The output resistance of the MAX870/MAX871
will typically be 20Ω plus two times the output resis-
tance of the buffer driving IN. The 0.1µF capacitor at
the IN pin absorbs the transient input currents of the
MAX870/MAX871.
INPUT
SHUTDOWN
LOGIC
SIGNAL
2
1
3
IN
C1-
C1
C
IN
0.1µF
MAX870
MAX871
5
4
OFF
C1+
ON
The output resistance of the buffer driving the IN pin
can be reduced by connecting multiple buffers in par-
allel. The polarity of the shutdown signal can also be
changed by using a noninverting buffer to drive IN.
OUTPUT
GND
OUT
C2
Figure 8. Shutdown Control
___________________Ch ip In fo rm a t io n
TRANSISTOR COUNT: 58
0/MAX871
SUBSTRATE CONNECTED TO IN
________________________________________________________P a c k a g e In fo rm a t io n
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8
___________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0
© 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
相关型号：
MAX870EUK+
Switched Capacitor Converter, 0.005A, 194kHz Switching Freq-Max, CMOS, PDSO5, SOT-23, 5 PIN
MAXIM
MAX870EUK-T
Switched Capacitor Converter, 0.005A, 194kHz Switching Freq-Max, CMOS, PDSO5, SOT-23, 5 PIN
MAXIM
MAX8710ETG
5V FIXED POSITIVE REGULATOR, QCC24, 4 X 4 MM, 0.8 MM PITCH, MO220WGGD-2, QFN-24
ROCHESTER
MAX8710ETG+T
Fixed Positive Standard Regulator, 5VBICMOS, 4 X 4 MM, 0.80 MM HEIGHT, ROHS COMPLIANT, MO-220WGGD-2, TQFN-16
MAXIM
©2020 ICPDF网 联系我们和版权申明