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MAX860IUA+ ,50mA, Frequency-Selectable, Switched-Capacitor Voltage ConvertersGeneral Description ________
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MAX860ESA-MAX860ISA-MAX860IUA-MAX861ESA-MAX861ISA-MAX861IUA
50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters
_______________General DescriptionThe 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.
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 (S—H—D—N–) 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 are available in 8-pin µMAXand
SO packages.
________________________ApplicationsPortable Computers
Medical Instruments
Interface Power Supplies
Hand-Held Instruments
Operational-Amplifier Power Supplies
____________________________Features8-Pin, 1.11mm High µMAX PackageInvert or Double the Input Supply VoltageThree Selectable Switching FrequenciesHigh Frequency Reduces Capacitor Size87% Efficiency at 50mA200µA Quiescent Current (MAX860)1µA Shutdown Supply Current600mV Voltage Drop at 50mA Load12ΩOutput Resistance
______________Ordering Information
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
__________________Pin Configuration
__________Typical Operating Circuit19-0239; Rev 1; 11/96
* Dice are tested at TA= +25°C, DC parameters only.Contact factory for availability.
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(Typical Operating Circuit (Inverter), VDD= +5V, –S—H—D—N–= VDD, FC = LV = GND, C1 = C2 = 10µF (Note 2), TA= TMINto TMAX, unless
otherwise noted. Typical values are at TA= +25°C.)
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.
Supply Voltage (VDDto GND or GND to OUT)...................+6.0V
Input Voltage Range (LV, FC, –S—H—D—N–) ...................(OUT - 0.3V)
to (VDD+ 0.3V)
Continuous Output Current (OUT, VDD).............................60mA
Output Short-Circuit to GND (Note 1)...................................1sec
Continuous Power Dissipation (TA= +70°C)
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
Operating Temperature Ranges
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
Note 1:OUT may be shorted to GND for 1sec without damage, but shorting OUT to VDDmay damage the device and should be
avoided. Also, for temperatures above +85°C, OUT must not be shorted to GND or VDD, even instantaneously, or device
damage may result.
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
ELECTRICAL CHARACTERISTICS (continued)(Typical Operating Circuit (Inverter), VDD= +5V, –S—H—D—N–= VDD, FC = LV = GND, C1 = C2 = 10µF (Note 2), TA= TMINto TMAX, unless
otherwise noted. Typical values are at TA= +25°C.)
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 0.2ΩESR 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 ⁄ (fsx C1) term in ROUT.
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
__________________________________________Typical Operating Characteristics(All curves generated using the inverter circuit shown in the Typical Operating Circuitswith LV = GND and TA= +25°C, unless other-
wise noted. Test results also valid for doubler mode with LV = OUT and TA= +25°C. All capacitor values used are those recom-
mended in Table 3, unless otherwise noted. The output resistance curves represent the resistance of the device itself, which is ROin
the equation for ROUTshown in the Capacitor Selection section.)
OUTPUT VOLTAGE DROP FROM
SUPPLY VOLTAGE vs. LOAD CURRENT
MAX860-01
LOAD CURRENT (mA)
OUT
DROP (V)
OSCILLATOR FREQUENCY vs.
SUPPLY VOLTAGEMAX860-02
SUPPLY VOLTAGE (V)
PERCENTAGE FREQUENCY CHANGE (
(FROM FREQUENCY MEASURED WITH V
= +5V)
OUTPUT SOURCE RESISTANCE (RO) vs.
SUPPLY VOLTAGE
MAX860-03
SUPPLY VOLTAGE (V)
OUTPUT SOURCE RESISTANCE (
OUTPUT SOURCE RESISTANCE (RO) vs.
TEMPERATURE
MAX860-04
TEMPERATURE (°C)
OUTPUT SOURCE RESISTANCE (100
MAX861 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX860-07
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
MAX860
EFFICIENCY vs. LOAD CURRENT
MAX860-05
LOAD CURRENT (mA)
EFFICIENCY (%)40
MAX860 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX860-06
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
MAX860 OUTPUT CURRENT vs. CAPACITANCE
HIGH-FREQUENCY MODE
MAX860-08
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
MAX860 OUTPUT CURRENT vs. CAPACITANCE
MEDIUM-FREQUENCY MODE
MAX860-09
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
4.72.222
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage ConvertersMAX861
OUTPUT CURRENT vs. CAPACITANCE
HIGH-FREQUENCY MODE
MAX860-10
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
MAX861
OUTPUT CURRENT vs. CAPACITANCE
MEDIUM-FREQUENCY MODE
MAX860-11
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
______________________________________________________________Pin Description
____________________________Typical Operating Characteristics (continued)
(All curves generated using the inverter circuit shown in the Typical Operating Circuitswith LV = GND and TA= +25°C, unless other-
wise noted. Test results also valid for doubler mode with LV = OUT and TA= +25°C. All capacitor values used are those recom-
mended in Table 3, unless otherwise noted. The output resistance curves represent the resistance of the device itself, which is ROin
the equation for ROUTshown in the Capacitor Selection section.)
_______________Detailed DescriptionThe 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.
Common Applications
Voltage InverterThe 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 Capacitorsection). Refer to the
Capacitor Selectionsection for suggested capacitor types
and values.
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 Selectionsection)
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 and supply voltage are shown in the Typical
Operating Characteristicsgraphs.
Calculate the output ripple voltage using the formula
given in the Capacitor Selectionsection.
Positive Voltage DoublerThe 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
Characteristicstable) 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.
Active-Low Shutdown InputWhen driven low, the –S—H—D—N–input shuts down the
device. In inverter mode, connect –S—H—D—N–to VDDif it is
not used. In doubler mode, connect –S—H—D—N–to GND if it
is not used. When the device is shut down, all active
circuitry is turned off.
In the inverting configuration, loads connected from
OUT to GND are not powered in shutdown mode.
However, a reverse-current path exists through two
diodes between OUT and GND; therefore, loads con-
nected from VDDto OUT draw current from the input
supply.
In the doubling configuration, loads connected from the
VDDpin to the GND pin are not powered in shutdown
mode. Loads connected from the VDDpin to the OUT
pin draw current from the input supply through a path
similar to that of the inverting configuration (described
above).
Frequency ControlCharge-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).
*See the Electrical Characteristics for detailed switching-
frequency specifications.
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
open). The spectrum of noise frequencies extends
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 InputLV 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.
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
Table 1. Nominal Switching Frequencies*
