Datasheet

MAX8614A/MAX8614B
Dual-Output (+ and -) DC-DC
Converters for CCD
9
Maxim Integrated
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/Voltage Positioning section).
Step-Up Converter
The step-up converter generates a positive output
voltage 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 internal load switch disconnects the battery from
the load by opening the battery connection to the
inductor, providing 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 cannot be bypassed.
LXN
V
CC
PVP
REF
FBN
ONBST
MAX8614A
MAX8614B
LXP
SEQ
ONINV
AVCC
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