Rainbow-electronics MAX1760 Manual do Utilizador descarregar pdf (Página 6)

MAX1760

0.8A, Low-Noise, 1MHz,

Step-Up DC-DC Converter

6 _______________________________________________________________________________________

NOISE SPECTRUM

MAX1760-13

1010.1

FREQUENCY (MHz)

NOISE (mV

RMS

)

TURN-ON WAVEFORMS

NO SOFT-START COMPONENTS

MAX1760-14

t = 2ms/div

A = ON, 5V/div

B = INPUT CURRENT, 500mA/div

C = V

OUT

, 2V/div

SOFT-START WAVEFORMS

= 500kΩ, C

= 0.1µF

MAX1760-15

2.00ms/div

A = ON, 5V/div

B = INPUT CURRENT, 100mA/div

C = V

OUT

, 2V/div

Pin Description

Typical Operating Characteristics (continued)

(Circuit of Figure 2, V

= 2.4V, V

OUT

= 3.3V, T

= +25°C, unless otherwise noted.)

Power Output. P-channel synchronous-rectifier source.

POUT9

Shutdown Control Input. When ON = high, the IC is in shutdown. Connect ON to GND for normal operation.ON

IC Power, Supplied from the Output. Bypass to GND with a 0.68µF ceramic capacitor, and connect to POUT

with a series 4.7Ω resistor (Figure 2).

OUT5

Clock Input for the DC-DC Converter. Also serves to program operating mode of switcher as follows:

CLK/SEL = LO: Normal operation—operates at a fixed frequency, automatically switching to low-power

mode if load is minimized.

CLK/SEL = HI: Forced PWM mode—operates in low-noise, constant-frequency mode at all loads.

CLK/SEL = Clocked: Forced PWM mode with the internal oscillator synchronized to CLK in 500kHz to

1200kHz range.

CLK/SEL6

Source of N-Channel Power MOSFET SwitchPGND7

Inductor ConnectionLX8

DC-DC Converter Feedback Input. To set fixed output voltage of +3.3V, connect FB to ground. For

adjustable output of 2.5V to 5.5V, connect to a resistive divider from OUT to GND. FB set point = 1.24V.

FB4

Ground. Connect to PGND with short trace. GND3

1.250V Voltage Reference Bypass. Connect a 0.22µF ceramic bypass capacitor to GND. Up to 50µA of

external load current is allowed.

REF2

N-Channel Current-Limit Control. For maximum current limit, connect to REF. To reduce current, supply a

voltage between REF and GND by means of a resistive voltage-divider. If soft-start is desired, connect a

capacitor from ISET to GND. When ON = high, or V

REF

<80% of nominal value, an on-chip 100kΩ switched

resistor discharges this pin to GND.

ISET1

FUNCTIONNAME

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

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