MAX861CSA-T [MAXIM]
Switched Capacitor Converter, 250kHz Switching Freq-Max, CMOS, PDSO8, 0.150 INCH, PLASTIC, SOIC-8;
| 型号： | MAX861CSA-T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Switched Capacitor Converter, 250kHz Switching Freq-Max, CMOS, PDSO8, 0.150 INCH, PLASTIC, SOIC-8 转换器 开关 |
| 文件： | 总12页 (文件大小：144K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0239; Rev 1; 11/96
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
0/MAX861
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ 8-Pin, 1.11mm High µMAX Package
♦ Invert or Double the Input Supply Voltage
♦ Three Selectable Switching Frequencies
♦ High Frequency Reduces Capacitor Size
♦ 87% Efficiency at 50mA
The MAX860/MAX861 charge-pump voltage converters
invert input voltages ranging from +1.5V to +5.5V, or
double input voltages ranging from +2.5V to +5.5V.
Because of their high switching frequencies, these
devices use only two small, low-cost capacitors. Their
50mA output makes switching regulators unnecessary,
eliminating inductors and their associated cost, size,
and EMI. Greater than 90% efficiency over most of the
load-current range, combined with a typical operating
current of only 200µA (MAX860), provides ideal perfor-
mance for both battery-powered and board-level volt-
age-conversion applications.
♦ 200µA Quiescent Current (MAX860)
♦ 1µA Shutdown Supply Current
♦ 600mV Voltage Drop at 50mA Load
♦ 12Ω Output Resistance
A frequency-control (FC) pin provides three switching-
frequencies to optimize capacitor size and quiescent
current and to prevent interference with sensitive cir-
cuitry. Each device has a unique set of three available
———–
frequencies. A shutdown (SHDN) pin reduces current
consumption to less than 1µA. The MAX860/MAX861
are suitable for use in applications where the ICL7660
and MAX660's switching frequencies are too low. The
MAX860/MAX861 a re a va ila b le in 8-p in µMAX a nd
SO packages.
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
-25°C to +85°C
-25°C to +85°C
0°C to +70°C
PIN-PACKAGE
8 SO
MAX860ISA
MAX860IUA
MAX860C/D
MAX860ESA
MAX860MJA
MAX861ISA
MAX861IUA
MAX861C/D
MAX861ESA
MAX861MJA
8 µMAX
Dice*
-40°C to +85°C
-55°C to +125°C
-25°C to +85°C
-25°C to +85°C
0°C to +70°C
8 SO
________________________Ap p lic a t io n s
Portable Computers
†
8 CERDIP
8 SO
Medical Instruments
8 µMAX
Dice*
8 SO
Interface Power Supplies
Hand-Held Instruments
-40°C to +85°C
-55°C to +125°C
Operational-Amplifier Power Supplies
†
8 CERDIP
* Dice are tested at T = +25°C, DC parameters only.
A
† Contact factory for availability.
__________Typ ic a l Op e ra t in g Circ u it
INPUT
VOLTAGE
+1.5V TO +5.5V
1
2
8
7
MAX860
MAX861
FC
V
DD
C1+
SHDN
__________________P in Co n fig u ra t io n
3
4
6
5
GND
C1-
LV
INVERTED
NEGATIVE
OUTPUT
C1 10µF
OUT
TOP VIEW
10µF
C2
VOLTAGE INVERTER
FC
C1+
GND
C1-
V
DD
1
2
3
4
8
7
6
5
INPUT
SHDN
LV
VOLTAGE
+2.5V TO +5.5V
DOUBLED
POSITIVE
OUTPUT
1
2
3
4
8
7
6
5
MAX860
MAX861
MAX860
MAX861
FC
V
DD
C1+
GND
C1-
SHDN
10µF
C2
OUT
LV
C1
10µF
SO/µMAX
OUT
POSITIVE VOLTAGE DOUBLER
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V to GND or GND to OUT)...................+6.0V
Operating Temperature Ranges
DD
–———–
Input Voltage Range (LV, FC, S HDN ) ...................(OUT - 0.3V)
MAX86_I_A ......................................................-25°C to +85°C
MAX86_ESA.....................................................-40°C to +85°C
MAX86_MJA ..................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
to (V + 0.3V)
DD
Continuous Output Current (OUT, V ) .............................60mA
DD
Output Short-Circuit to GND (Note 1)...................................1sec
Continuous Power Dissipation (T = +70°C)
A
SO (derate 5.88mW/°C above +70°C).........................471mW
µMAX (derate 4.10mW/°C above +70°C) ....................330mW
CERDIP (derate 8.00mW/°C above +70°C).................640mW
Note 1: OUT may be shorted to GND for 1sec without damage, but shorting OUT to V may damage the device and should be
DD
avoided. Also, for temperatures above +85°C, OUT must not be shorted to GND or V , even instantaneously, or device
DD
damage may result.
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.
0/MAX861
ELECTRICAL CHARACTERISTICS
–———–
(Typical Operating Circuit (Inverter), V = +5V, SHDN= V , FC = LV = GND, C1 = C2 = 10µF (Note 2), T = T
to T , unless
MAX
DD
A
MIN
DD
otherwise noted. Typical values are at T = +25°C.)
A
PARAMETER
Supply Voltage
SYMBOL
CONDITIONS
Inverter, LV = GND
Doubler, LV = OUT
FC = V = 5V
MIN
1.5
TYP
MAX
5.5
UNITS
V
DD
R
= 1kΩ
L
V
2.5
5.5
0.2
0.07
0.6
0.3
DD
FC = V = 3V
DD
MAX860I/E
FC = GND
FC = OUT
1.0
2.5
0.4
1.3
3.3
0.4
2.0
5.0
0.5
2.6
6.5
1.4
FC = V
DD
MAX860M
MAX861I/E
MAX861M
FC = GND
FC = OUT
No-Load Supply Current
I
DD
mA
FC = V
0.3
1.1
2.5
DD
FC = GND
FC = OUT
FC = V
DD
FC = GND
FC = OUT
V
= 5V, V
more negative than -3.75V
more negative than -2.5V
50
10
100
30
DD
OUT
Output Current
I
mA
OUT
V
DD
= 3V, V
OUT
I = 50mA
12
20
25
35
L
Output Resistance
(Note 3)
R
Ω
OUT
I = 10mA, V = 2V
L
DD
2
_______________________________________________________________________________________
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
0/MAX861
ELECTRICAL CHARACTERISTICS (continued)
–———–
(Typical Operating Circuit (Inverter), V = +5V, SHDN = V , FC = LV = GND, C1 = C2 = 10µF (Note 2), T = T
to T , unless
MAX
DD
DD
A
MIN
otherwise noted. Typical values are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
FC = V
MIN
3
TYP
6
MAX
UNITS
kHz
DD
MAX860
FC = GND
FC = OUT
30
80
8
50
130
13
Switching Frequency
(Note 4)
f
S
FC = V
DD
MAX861
FC < 4V
FC = GND
FC = OUT
60
160
100
250
-2
FC Current (from V
)
I
FC
-4
µA
DD
R
= 2kΩ from V
DD
L
93
90
93
88
96
93
to OUT
MAX860,
FC = V
DD
R
= 1kΩ from OUT
L
to GND
R
= 2kΩ from V
L
DD
Power Efficiency (Note 5)
96
%
to OUT
MAX861,
FC = V
DD
R
= 1kΩ from OUT
L
92
to GND
MAX860/MAX861, FC = V
I = 50mA to GND, C1 = C2 = 68µF
L
,
DD
87
Voltage-Conversion Efficiency
No load
99
99.9
%
V
V
LV = GND
1.2
IH
–———–
SHDN Threshold
V
IL
0.3
1
MAX86_I/E
MAX86_M
–———–
S HDN < 0.3V
Shutdown Supply Current
Time to Exit Shutdown
µA
µs
10
No load, V
= -4V
500
OUT
Note 2: C1 and C2 are low-ESR (<0.2Ω) aluminum electrolytics. Capacitor ESR adds to the circuit’s output resistance. Using
capacitors with higher ESR may reduce output voltage and efficiency.
Note 3: Specified output resistance includes the effect of the 0.2Ω ESR of the test circuit’s capacitors.
Note 4: The switches are driven directly at the oscillator frequency, without any division.
Note 5: At lowest frequencies, using 10µF capacitors gives worse efficiency figures than using the recommended capacitor
values in Table 3, due to larger 1 ⁄ (f x C1) term in R
.
s
OUT
_______________________________________________________________________________________
3
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(All curves generated using the inverter circuit shown in the Typical Operating Circuits with LV = GND and T = +25°C, unless other-
A
wise noted. Test results also valid for doubler mode with LV = OUT and T = +25°C. All capacitor values used are those recom-
A
mended in Table 3, unless otherwise noted. The output resistance curves represent the resistance of the device itself, which is R in
O
the equation for R
shown in the Capacitor Selection section.)
OUT
OSCILLATOR FREQUENCY vs.
SUPPLY VOLTAGE
OUTPUT VOLTAGE DROP FROM
SUPPLY VOLTAGE vs. LOAD CURRENT
OUTPUT SOURCE RESISTANCE (R ) vs.
O
SUPPLY VOLTAGE
2
0
0.8
0.7
0.6
0.5
0.4
20
18
16
14
12
10
8
ALL FREQUENCIES
V
DD
= +1.5V
V
DD
= +2.5V
-2
-4
-6
-8
0.3
0.2
6
V
= +3.5V
-10
-12
-14
DD
0/MAX861
4
ALL FREQUENCIES,
LV CONNECTED TO GND
(INVERTER) OR OUT (DOUBLER)
V
= +4.5V, +5.0V
DD
0.1
0
2
V
DD
= +5.5V
ALL FREQUENCIES
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
0
10
20
30
40
50
0
1
2
3
4
5
LOAD CURRENT (mA)
SUPPLY VOLTAGE (V)
OUTPUT SOURCE RESISTANCE (R ) vs.
O
MAX860 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX860
EFFICIENCY vs. LOAD CURRENT
TEMPERATURE
32
28
100
500
400
ALL FREQUENCIES
FC = V
DD
90
80
70
60
50
40
30
20
10
0
DOUBLER, LV = OUT
24
20
V
DD
= +1.5V
V
= +1.5V
= +5V
DD
300
200
100
0
V
DD
= +3V
16
12
8
INVERTER, LV = GND
(V > 3V)
V
DD
= +5V
V
DD
= +3V
DD
V
DD
INVERTER
FC = V
4
0
DD
-60 -40 -20
0
20 40 60 80 100 120 140
0.01
0.1
1
10
100
0
1
2
3
4
5
6
TEMPERATURE (°C)
LOAD CURRENT (mA)
SUPPLY VOLTAGE (V)
MAX860 OUTPUT CURRENT vs. CAPACITANCE
HIGH-FREQUENCY MODE
MAX860 OUTPUT CURRENT vs. CAPACITANCE
MEDIUM-FREQUENCY MODE
MAX861 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
70
60
50
80
70
60
50
500
400
f
= 130kHz
OSC
f
= 50kHz
OSC
FC = V
DD
FC = OUT
LV = GND
INVERTER MODE
FC = GND
LV = GND
INVERTER MODE
DOUBLER, LV = OUT
V
= +4.5V, V
= -4V
= -3.5V
= -2.4V
IN
OUT
V
= +4.5V, V
= -3.5V
= -2.4V
IN
OUT
V
IN
= +4.5V, V
OUT
300
200
100
0
40
30
40
V
= +3V, V
OUT
IN
INVERTER, LV = GND
V
= +3V, V
OUT
IN
30
20
V
= +4.5V, V
= -4V
IN
OUT
20
10
0
V
IN
= +3V, V
= -2.7V
V
= +3V, V
= -2.7V
OUT
IN
OUT
10
0
0.33
1
2.2
4.7
10
22
0.33
1
2.2
4.7
10
22
0
1
2
3
4
5
6
CAPACITANCE (µF)
CAPACITANCE (µF)
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
0/MAX861
____________________________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 )
(All curves generated using the inverter circuit shown in the Typical Operating Circuits with LV = GND and T = +25°C, unless other-
A
wise noted. Test results also valid for doubler mode with LV = OUT and T = +25°C. All capacitor values used are those recom-
A
mended in Table 3, unless otherwise noted. The output resistance curves represent the resistance of the device itself, which is R in
O
the equation for R
shown in the Capacitor Selection section.)
OUT
MAX861
MAX861
OUTPUT CURRENT vs. CAPACITANCE
HIGH-FREQUENCY MODE
OUTPUT CURRENT vs. CAPACITANCE
MEDIUM-FREQUENCY MODE
90
80
70
60
50
40
30
20
10
0
80
70
60
50
f
= 100kHz
f
= 250kHz
OSC
OSC
FC = GND
FC = OUT
V
IN
= +4.5V,
LV = GND
LV = GND
INVERTER MODE
V
OUT
= -3.5V
V
V
OUT
= +4.5V,
= -3.5V
IN
INVERTER MODE
V
IN
= +3V,
40
V
OUT
= -2.4V
V
IN
= +4.5V, V
= -4V
OUT
V
IN
= +4.5V,
30
20
V
OUT
= -4V
V
IN
= +3V, V
= -2.4V
OUT
V
IN
= +3V, V
= -2.7V
OUT
10
0
V
IN
= +3V, V
= -2.7V
OUT
0.33
1
2.2
4.7
10
22
0.33
1
2.2
4.7
10
22
CAPACITANCE (µF)
CAPACITANCE (µF)
______________________________________________________________P in De s c rip t io n
FUNCTION
PIN
NAME
INVERTER
Frequency Control, see Table 1
Flying-Capacitor Positive Terminal
Ground
DOUBLER
Frequency Control, see Table 1
Flying-Capacitor Positive Terminal
Positive Input Supply
1
2
3
4
5
6
FC
C1+
GND
C1-
Flying-Capacitor Negative Terminal
Negative Output
Flying-Capacitor Negative Terminal
Ground
OUT
LV
Low-Voltage-Operation Input. Connect to GND.
Low-Voltage-Operation Input. Connect to OUT.
–———–
SHDN
Active-Low Shutdown Input. Connect to V if not
DD
used. Connect to GND to disable the charge pump.
Active-Low Shutdown Input. Connect to GND pin if not
used. Connect to OUT to disable the charge pump.
7
8
V
DD
Positive Input Supply
Doubled Positive Output
_______________________________________________________________________________________
5
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
is not used. When the device is shut down, all active
circuitry is turned off.
_______________De t a ile d De s c rip t io n
The MAX860/MAX861 capacitive charge pumps either
invert or double the voltage applied to their inputs. For
highest performance, use low equivalent series resis-
tance (ESR) capacitors. See the Capacitor Selection
section for more details. The frequency-control (FC) pin
allows you to choose one of three switching frequen-
cies; these three selectable frequencies are different for
each device. When shut down, MAX860/MAX861 cur-
rent consumption reduces to less than 1µA.
In the inverting configuration, loads connected from
OUT to GND a re not p owe re d in s hutd own mod e .
However, a reverse-current path exists through two
diodes between OUT and GND; therefore, loads con-
nected from V
to OUT draw current from the input
DD
supply.
In the doubling configuration, loads connected from the
pin to the GND pin are not powered in shutdown
V
DD
mode. Loads connected from the V
pin to the OUT
DD
Co m m o n Ap p lic a t io n s
pin draw current from the input supply through a path
similar to that of the inverting configuration (described
above).
Voltage Inverter
The most common application for these devices is a
charge-pump voltage inverter (see Typical Operating
Circuits). This application requires only two external com-
ponents—capacitors C1 and C2—plus a bypass capacitor
if necessary (see Bypass Capacitor section). Refer to the
Capacitor Selection section for suggested capacitor types
and values.
Fre q u e n c y Co n t ro l
Charge-pump frequency for both devices can be set to
one of three values. Each device has a unique set of
three available frequencies, as indicated in Table 1.
The oscillator and charge-pump frequencies are the
same (i.e., the charge-pump frequency is not half the
oscillator frequency, as it is on the MAX660, MAX665,
and ICL7660).
0/MAX861
Even though the MAX860/MAX861’s output is not actively
regulated, it is fairly insensitive to load-current changes. A
circuit output source resistance of 12Ω (calculated using
the formula given in the Capacitor Selection section)
means that, with a +5V input, the output voltage is -5V
under no load and decreases to -4.4V with a 50mA load.
The MAX860/MAX861 output source resistance (used to
calculate the circuit output source resistance) vs. tempera-
ture a nd s up p ly volta g e a re s hown in the Typ ic a l
Operating Characteristics graphs.
Table 1. Nominal Switching Frequencies*
FREQUENCY (kHz)
FC CONNECTION
MAX860
MAX861
FC = V or open
DD
6
13
FC = GND
FC = OUT
50
100
Calculate the output ripple voltage using the formula
given in the Capacitor Selection section.
130
250
*See the Electrical Characteristics for detailed switching-
frequency specifications.
Positive Voltage Doubler
The MAX860/MAX861 can also operate as positive volt-
age doublers (see Typical Operating Circuits). This
application requires only two external components,
capacitors C1 and C2. The no-load output is twice the
input voltage. The electrical specifications in the doubler
mode are very similar to those of the inverter mode
except for the Supply Voltage Range (see Electrical
Characteristics table) and No-Load Supply Current (see
graph in Typical Operating Characteristics). The circuit
output source resistance and output ripple voltage are
calculated using the formulas in the Capacitor Selection
section.
A higher switching frequency minimizes capacitor size
for the same performance and increases the supply
current (Table 2). The lowest fundamental frequency of
the switching noise is equal to the minimum specified
switching frequency (e.g., 3kHz for the MAX860 with FC
op e n). The s p e c trum of nois e fre q ue nc ie s e xte nd s
above this value because of harmonics in the switching
waveform. To get best noise performance, choose the
device and FC connection to select a minimum switch-
ing frequency that lies above your sensitive bandwidth.
Low-Voltage-Operation Input
LV should be connected to GND for inverting operation.
To enhance compatibility with the MAX660, MAX665, and
ICL7660, you may float LV if the input voltage exceeds 3V.
In doubling mode, LV must be connected to OUT for all
input voltages.
Ac t ive -Lo w S h u t d o w n In p u t
–———–
Whe n d rive n low, the SHDN inp ut s huts d own the
–———–
device. In inverter mode, connect SHDN to V
not used. In doubler mode, connect SHDN to GND if it
if it is
DD
–———–
6
_______________________________________________________________________________________
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
0/MAX861
A typical design procedure is as follows:
Table 2. Switching-Frequency Trade-Offs
1) Choose C1 and C2 to be the same, for convenience.
2) Select f :
LOWER
FREQUENCY
HIGHER
FREQUENCY
S
ATTRIBUTE
a) If you want to avoid a specific noise frequency,
Output Ripple
C1, C2 Values
Supply Current
Larger
Larger
Smaller
Smaller
Smaller
Larger
choose f appropriately.
S
b) If you want to minimize capacitor cost and size,
choose a high f .
S
c) If you want to minimize current consumption,
__________Ap p lic a t io n s In fo rm a t io n
choose a low f .
S
3) Choose a capacitor based on Table 3, although
higher or lower values can be used to optimize per-
formance. Table 4 lists manufacturers who provide
low-ESR capacitors.
Ca p a c it o r S e le c t io n
The MAX860/MAX861 are tested using 10µF capacitors
for both C1 and C2, although smaller or larger values
can be used (Table 3). Smaller C1 values increase the
outp ut re s is ta nc e ; la rg e r va lue s re d uc e the outp ut
re s is ta nc e . Ab ove a c e rta in p oint, inc re a s ing the
capacitance of C1 has a negligible effect (because the
output resistance becomes dominated by the internal
switch resistance and the capacitor ESR). Low-ESR
capacitors provide the lowest output resistance and
ripple voltage. The output resistance of the entire circuit
(inverter or doubler) is approximately:
Table 3. Suggested Capacitor Values*
NOMINAL FREQUENCY (kHz)
C1, C2 (µF)
6
68
47
13
50
10
R
= R + 4 x ESR + ESR + 1 / (f x C1)
O C1 C2 S
OUT
100
130
250
4.7
4.7
2.2
where R (the effective resistance of the MAX860/
O
MAX861’s internal switches) is approximately 8Ω and f
S
is the switching frequency. R
is typically 12Ω when
OUT
using capacitors with 0.2Ω ESR and f , C1, and C2 val-
S
ues suggested in Table 3. When C1 and C2 are so
large (or the switching frequency is so high) that the
internal switch resistance dominates the output resis-
tance, estimate the output resistance as follows:
*In a d d ition to Ta b le 3, four g ra p hs in the Typ ic a l
Operating Characteristics section show typical output
c urre nt for C1 a nd C2 c a p a c ita nc e s ra ng ing from
0.33µF to 22µF. Output current is plotted for inputs of
4.5V (5V - 10%) and 3.0V (3.3V - 10%), and also for
R
= R + 4 x ESR + ESR
O C1 C2
OUT
10% and 20% output droop from the ideal -V value.
IN
Table 4. Low-ESR Capacitor Manufacturers
MANUFACTURER–Series
AVX TPS Series
PHONE
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_______________________________________________________________________________________
7
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
Flying Capacitor, C1
Increasing the size of the flying capacitor reduces the
output resistance.
unloaded output voltage is nominally -2 x V , but this is
IN
reduced slightly by the output resistance of the first
device multiplied by the quiescent current of the sec-
ond. The output resistance of the complete circuit is
approximately five times the output resistance of a sin-
gle MAX860/MAX861.
Output Capacitor, C2
Increasing the size of the output capacitor reduces the
output ripple voltage. Decreasing its ESR reduces both
output resistance and ripple. Smaller capacitance val-
ues can be used if one of the higher switching frequen-
cies is selected, if less than the maximum rated output
current (50mA) is required, or if higher ripple can be
tolerated. The following equation for peak-to-peak rip-
ple applies to both the inverter and doubler circuits.
Three or more devices can be cascaded in this way,
but output resistance rises dramatically, and a better
solution is offered by inductive switching regulators
(such as the MAX755, MAX759, MAX764, or MAX774).
Connect LV as with a standard inverter circuit (see Pin
Description).
P a ra lle lin g De vic e s
Paralleling multiple MAX860s or MAX861s reduces the
outp ut re s is ta nc e . As illus tra te d in Fig ure 2, e a c h
device requires its own pump capacitor (C1), but the
reservoir capacitor (C2) serves all devices. C2’s value
should be increased by a factor of n, where n is the
number of devices. Figure 2 shows the equation for cal-
culating output resistance. An alternative solution is to
use the MAX660 or MAX665, which are capable of sup-
plying up to 100mA of load current. Connect LV as with
a standard inverter circuit (see Pin Description).
I
OUT
V
= ———————— + 2 x I
x ESR
RIPPLE
OUT C2
2 x f x C2
S
0/MAX861
Bypass Capacitor
Bypass the incoming supply to reduce its AC impedance
and the impact of the MAX860/MAX861’s switching
noise. The recommended bypassing depends on the cir-
cuit configuration and where the load is connected.
When the inverter is loaded from OUT to GND or the
doubler is loaded from V
to GND, current from the
DD
supply switches between 2 x I
use a large bypass capacitor (e.g., equal to the value
of C1) if the supply has a high AC impedance.
and zero. Therefore,
Co m b in e d Do u b le r/In ve rt e r
In the circuit of Figure 3, 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
capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline towards GND. Make
sure the sum of the currents drawn from the two out-
puts does not exceed 60mA. Connect LV as with a
standard inverter circuit (see Pin Description).
OUT
When the inverter and doubler are loaded from V to
DD
OUT, the circuit draws 2 x I
constantly, except for
OUT
short switching spikes. A 0.1µF bypass capacitor is
sufficient.
Ca s c a d in g De vic e s
Two devices can be cascaded to produce an even
larger negative voltage, as shown in Figure 1. The
R
OF SINGLE DEVICE
OUT
R
OUT
=
NUMBER OF DEVICES
…
IN
…
+V
+V
IN
8
7
8
7
8
7
8
2
3
2
3
2
3
2
3
7
MAX860
MAX861
“1”
MAX860
MAX861
“n”
C1
C1
MAX860
MAX861
“1”
MAX860
MAX861
“n”
C1
C1
V
OUT
5
4
5
4
V
OUT
5
4
5
4
…
C2
C2
…
C2
V
OUT
= -V
IN
V
OUT
= -nV
IN
Figure 2. Paralleling MAX860s or MAX861s to Reduce Output
Resistance
Figure 1. Cascading MAX860s or MAX861s to Increase
Output Voltage
8
_______________________________________________________________________________________
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
0/MAX861
Table 5. Product Selection Guide
+V
IN
OUTPUT
OUTPUT
SWITCHING
8
7
PART
NUMBER
CURRENT RESISTANCE FREQUENCY
2
3
(mA)
100
100
50
(Ω)
6.5
6.5
12
(kHz)
5/40
D1, D2 = 1N4148
MAX860
MAX861
C1
D1
D2
MAX660
MAX665
MAX860
MAX861
ICL7660
4
5
V
OUT
= -V
IN
C2
C4
5/40
6/50/130
13/100/250
5
V
= (2V ) -
IN
OUT
(V ) - (V
)
FD1
FD2
50
12
C3
10
55
Figure 3. Combined Doubler and Inverter
Co m p a t ib ilit y w it h
MAX6 6 0 /MAX6 6 5 /ICL7 6 6 0
___________________Ch ip To p o g ra p h y
The MAX860/MAX861 c a n b e us e d in s oc ke ts
designed for the MAX660, MAX665, and ICL7660 with
a minimum of one wiring change. This section gives
advice on installing a MAX860/MAX861 into a socket
designed for one of the earlier devices.
V
DD
FC
0. 084"
(2. 13mm)
C1+
The MAX660, MAX665, and ICL7660 have an OSC pin
–———–
instead of SHDN. MAX660, MAX665, and ICL7660 nor-
mal operation is with OSC floating (although OSC can
be overdriven). If OSC is floating, pin 7 (SHDN ) should
GND
–———–
SHDN
be jumpered to V
p e rma ne ntly. Do not le a ve SHDN on the MAX860/
MAX861 floating.
to enable the MAX860/MAX861
DD
–———–
C1-
LV
The MAX860/MAX861 operate with FC either floating or
OUT
connected to V , OUT, or GND; each connection
DD
defines the oscillator frequency. Thus, any of the nor-
mal MAX660, MAX665, or ICL7660 connections to pin 1
will work with the MAX860/MAX861, without modifica-
tions. Changes to the FC connection are only required
if you want to adjust the operating frequency.
0. 058"
(1. 47mm)
TRANSISTOR COUNT: 101
SUBSTRATE CONNECTED TO V
DD
_______________________________________________________________________________________
9
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
________________________________________________________P a c k a g e In fo rm a t io n
0/MAX861
10 ______________________________________________________________________________________
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
0/MAX861
___________________________________________P a c k a g e In fo rm a t io n (c o n t in u e d )
______________________________________________________________________________________ 11
5 0 m A, Fre q u e n c y-S e le c t a b le ,
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
NOTES
0/MAX861
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.
12 __________________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
© 1996 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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