19-1353; Rev 0; 4/98
KIT
ATION
EVALU
BLE
AVAILA
Dual-Output (Positive and Negative),
DC-DC Converter for CCD and LCD
General Description
Features
o
Dual Output Using a Single Inductor
o
Low-Noise Output, 30mVp-p Ripple
o
Output Voltages up to 24V and down to -9V
(up to 45V and down to -16V with added
components)
o
Internal Switches in a Small Package
o
220kHz/400kHz Fixed-Frequency PWM Operation
o
Frequency Can Be Synchronized to
External Clock
o
Power-OK Indicator
o
Selectable Power-On Sequencing
o
0.1µA Logic-Controlled Shutdown
MAX685
The MAX685 DC-DC converter provides low-noise dual
outputs for powering CCD imaging devices and LCDs.
This device uses a single inductor to provide indepen-
dently regulated positive and negative outputs.
Integrated power switches are included in the small
16-pin QSOP package (same size as an 8-pin SO) to
save space and reduce cost.
Each output delivers up to 10mA from a +2.7V to +5.5V
input voltage range. Output voltages are set indepen-
dently up to 24V and down to -9V. With a few additional
low-cost components, the output voltages can be set at
up to 45V and down to -16V. Output ripple magnitude is
30mVp-p. The MAX685 uses a fixed-frequency, pulse-
width-modulated (PWM) control scheme at 220kHz or
400kHz to permit output noise filtering and to reduce
the size of external components. The frequency can
also be synchronized to an external clock signal
between 200kHz and 480kHz.
The MAX685 has a power-OK indicator output (POK)
that signals when both outputs are within regulation. A
logic-controlled shutdown completely turns off both out-
puts and reduces supply current to 0.1µA. The user
can also set which output turns on first.
The preassembled MAX685 evaluation kit is available to
reduce design time.
Ordering Information
PART
MAX685EEE
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 QSOP
Applications
Camcorders
Digital Cameras
Notebooks
LCDs
CCD Imaging Devices
INPUT
2.7V TO 5.5V
Typical Operating Circuit
VP
LXN
Pin Configuration
TOP VIEW
LXP 1
I.C. 2
VP 3
POK 4
SEQ 5
SHDN 6
SYNC 7
V
DD
8
16 LXN
15 I.C.
14 PGND
OPTIONAL
POS
12 FBP
11 REF
10 FBN
9
GND
POWER-OK
INDICATOR
NEG
ON
OFF
V
DD
FBP
SHDN
POSITIVE
OUTPUT
UP TO 24V,
10mA
MAX685
SYNC
LXP
MAX685
13 PGND
SEQ
FBN
NEGATIVE
OUTPUT
DOWN TO -9V,
10mA
POK
GND
REF
QSOP
I.C. = INTERNALLY CONNECTED
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
