Rainbow-electronics MAX8614B Manual de usuario descargar pdf (Pagina 9)

MAX8614A/MAX8614B

Dual-Output (+ and -) DC-DC

Converters for CCD

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Detailed Description

The MAX8614A/MAX8614B generate both a positive and

negative output voltage by combining a step-up and an

inverting DC-DC converter on one IC. Both the step-up

converter and the inverter share a common clock. Each

output is independently regulated.

Each output is separately controlled by a pulse-width-

modulated (PWM) current-mode regulator. This allows

the converters to operate at a fixed frequency (1MHz)

for use in noise-sensitive applications. The 1MHz

switching rate allows for small external components.

Both converters are internally compensated and are

optimized for fast transient response (see the Load-

Transient Response/Voltage Positioning section).

Step-Up Converter

The step-up converter generates a positive output volt-

age up to 24V. An internal power switch, internal True-

Shutdown load switch (PVP), and external catch diode

allow conversion efficiencies as high as 90%. The inter-

nal load switch disconnects the battery from the load

by opening the battery connection to the inductor, pro-

viding True Shutdown. The internal load switch stays on

at all times during normal operation. The load switch is

used in the control scheme for the converter and can-

not be bypassed.

LXN

PVP

REF

FBN

ONBST

MAX8614A

MAX8614B

LXP

SEQ

ONINV

GND

PGND

FBP

1MHz

OSCILLATOR

REFERENCE

1.25V

STEP-UP

CURRENT SENSE

INVERTER

CURRENT SENSE

SOFT-START

ERROR

AMPLIFIER

PWM

COMPARATOR

INVERTER

CONTROL

LOGIC

BIAS

AND

CONTROL

BLOCK

1.01V

ERROR

AMPLIFIER

PWM

COMPARATOR

STEP-UP

CONTROL

LOGIC

FLT

Functional Diagram

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

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Rainbow-electronics MAX8614B Manual de usuario Pagina 9

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