MAX1765 データシートの表示（PDF） - Maxim Integrated

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MAX1765

800mA, Low-Noise, Step-Up DC-DC Converter with 500mA Linear Regulator

Maxim Integrated 

800mA, Low-Noise, Step-Up DC-DC Converter

with 500mA Linear Regulator

(TA = +25°C, unless otherwise noted.)

LIGHT-LOAD SWITCHING WAVEFORMS

(VIN = +2.4V, VOUT = +3.3V, IOUT = 10mA)

MAX1765 toc17

A

B

C

500ns/div

A: LX NODE, 5V/div

B: INDUCTOR CURRENT, 200mA/div, AC-COUPLED

C: OUTPUT RIPPLE, 20mV/div, AC-COUPLED

Typical Operating Characteristics (continued)

LINEAR-REGULATOR OUTPUT NOISE

450

ILDO = 200mA

VLDO = 2.85V

350

250

150

50

0

0.1

1

10

FREQUENCY (MHz)

SWITCH CURRENT LIMIT vs. VISET

1.4

VOUT = +3.3

1.2

1.0

0.8

0.6

0.4

0.2

0

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

VISET (V)

Pin Description

PIN

NAME

FUNCTION

Low-Dropout Linear Regulator Dual-Mode Feedback Input. Connect FBL to ground for 2.85V nominal

1

FBL

output voltage. Connect FBL to a resistor-divider from OUTL to ground for an adjustable output voltage.

FBL regulates to 1.25V.

Set N-Channel Current Limit. For maximum current limit, connect ISET to REF. To reduce current limit,

2

ISET

use a resistor-divider from REF to GND. If soft-start is desired, a capacitor can be added from ISET to

GND. When ONA = LO and ONB = HI or VREF < 80% of nominal value, an on-chip 100kΩ switchable

resistor discharges ISET to GND.

3

REF

1.25V Reference Output. Connect a 0.22µF bypass capacitor to GND; 50µA of external load current is

allowed. The reference is enabled if ONA = HI, ONB = LO, or ONL = HI.

4

GND Ground. Connect to PGND with short trace.

5

FB

Boost Converter Feedback Input. Connect a resistor-divider between OUT and GND to set the output

voltage in the range of 2.5V to 5V. In track mode, FB is disabled after OUTL is in regulation.

6

OUT

Boost Converter IC power is derived from OUT. Connect OUT to POUT through a 4.7Ω resistor and

bypass to GND with a 0.68µF capacitor.

7

ONA ON Input. When high, the DC-DC is operational (Table 2).

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

CLK/SEL = LOW: Normal mode. Operates at a fixed frequency, automatically switching to low-power

8

CLK/SEL

(SKIP) mode when the load is minimized.

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

CLK/SEL = Clocked: Synchronized forced PWM mode. The internal oscillator is synchronized to an

external clock in the 500kHz to 1200kHz frequency range.

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