MAX8969EWL53 データシートの表示（PDF） - Maxim Integrated

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MAX8969EWL53

Step-Up Converter for Handheld Applications

Maxim Integrated 

MAX8969

Step-Up Converter for Handheld Applications

MAX8969

OUT_

COUT

22µF

IN

CIN

4.7µF

TREN

EN

REFERENCE

ATM

COMPARATOR

RAMP

GENERATOR

IN

0.95 x

VOUT_TARGET

CONTROL

LOGIC

IN

ATM

TRACK

ENABLE

PWM

LOGIC

CURRENT

LIMIT

L1

1µH

P1

TRUE

SHUTDOWN

N1

GND_ LX_

Figure 1. Functional Diagram

Detailed Description

The MAX8969 is a step-up DC-DC switching converter

that utilizes a fixed-frequency PWM architecture with True

Shutdown. With an advanced voltage-positioning control

scheme and high 3MHz switching frequency, the IC is inex-

pensive to implement and compact, using only a few small

easily obtained external components. Under light-load

conditions, the IC switches only when needed, consum-

ing only 45µA (typ) of quiescent current. The IC is highly

efficient with an internal switch and synchronous rectifier.

Shutdown typically reduces the quiescent current to 1µA

(typ). Low quiescent current and high efficiency make this

device ideal for powering portable equipment.

Internal soft-start limits inrush current to less than 480mA

(typ), while output voltage is less than input voltage. Once

output voltage approaches input voltage approaches

input voltage after a brief delay, output voltage is boosted

to its final value at a rate of approximately 25mV/µs.

During this period, as well as being limited by the voltage,

ramp rate current is limited by the normal 2.6A boost

mode current limit.

In boost mode, the step-up converter boosts to

VOUT_TARGET from battery input voltages ranging from

2.5V to VOUT_TARGET. When the input voltage ranges

from 0.95 x VOUT_TARGET to 5.5V, the IC enters ATM

and the output voltage approximately follows the input

voltage. During boost mode, the input current limit is set

to 2.6A to guarantee delivery of the rated out current (e.g.,

1A output current when boosting from a 2.5V input supply

to a 3.7V output).

Control Scheme

The step-up converter uses a load/line control scheme.

The load/line control scheme allows the output voltage

to sag under load, but prevents overshoot when the

load is suddenly removed. The load/line control scheme

reduces the total range of voltages reached during tran-

sients at the expense of DC output impedance.

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