Detailed description, Functional diagram – Rainbow Electronics MAX8614B User Manual

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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