MAX1044CSLASHD datasheet(10/14 Pages) MAXIM

10 / 14 page

Increasing Efficiency

Efficiency can be improved by lowering output voltage

ripple and output impedance. Both output voltage ripple

and output impedance can be reduced by using large

capacitors with low ESR.

The output voltage ripple can be calculated by noting that

the output current is supplied solely from capacitor C2

during one-half of the charge-pump cycle.

RIPPLET

C2 OUT

OSC

2 x ESR

2 f

x C2



≅+





Slowing the oscillator frequency reduces quiescent

current. The oscillator frequency can be reduced by

connecting a capacitor to the OSC pin.

Reducing the oscillator frequency increases the rip-

ple voltage in the MAX1044/ICL7660. Compensate by

increasing the values of the bucket and reservoir capaci-

tors. For example, in a negative voltage converter, the

pump frequency is around 4kHz or 5kHz. With the rec-

ommended 10μF bucket and reservoir capacitors, the

circuit consumes about 70μA of quiescent current while

providing 20mA of output current. Setting the oscillator to

400Hz by connecting a 100pF capacitor to OSC reduces

the quiescent current to about 15μA. Maintaining 20mA

output current capability requires increasing the bucket

and reservoir capacitors to 100μF.

Note that lower capacitor values can be used for lower

output currents. For example, setting the oscillator to

40Hz by connecting a 1000pF capacitor to OSC provides

the highest efficiency possible. Leaving the bucket and

reservoir capacitors at 100μF gives a maximum IOUT of

2mA, a no-load quiescent current of 10μA, and a power

conversion efficiency of 98%.

General Precautions

1) Connecting any input terminal to voltages greater

than V+ or less than ground may cause latchup. Do

not apply any input sources operating from external

supplies before device power-up.

2) Never exceed maximum supply voltage ratings.

3) Do not connect C1 and C2 with the wrong polarity.

4) Do not short V+ to ground for extended periods with

supply voltages above 5.5V present on other pins.

5) Ensure that VOUT (pin 5) does not go more positive

than GND (pin 3). Adding a diode in parallel with C2,

with the anode connected to VOUT and cathode to LV,

will prevent this condition.

Application Circuits

Negative Voltage Converter

Figure 8 shows a negative voltage converter, the most

popular application of the MAX1044/ICL7660. Only two

external capacitors are needed. A third power-supply

bypass capacitor is recommended (0.1μF to 10μF)

Figure 9. Voltage Doubler

Figure 8. Negative Voltage Converter with BOOST and LV

Connections

MAX1044

ICL7660

10µF

VOUT = -(V+)

CBYPASS

0.1µF

10µF

V+

BOOST

MAX1044

ICL7660

VOUT = 2(V+) - 2VD

V+

MAX1044/ICL7660

Switched-Capacitor Voltage Converters

www.maximintegrated.com

Maxim Integrated │ 10

MAX1044C/D Datasheet(PDF) 10 Page - Maxim Integrated Products

MAX1044C/D Datasheet(HTML) 10 Page - Maxim Integrated Products

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Datasheet Download

Link URL