C
CS
Capacitor Selection
C
CS
is the output of the boost converter and provides
the high-voltage source for the EL lamp. Connect a
3.3nF capacitor from CS to GND and place as close to
the CS input as possible.
Diode Selection
Connect a diode, D1, from the LX node to CS to rectify
the boost voltage on CS. The diode should be a fast
recovery diode that is tolerant to +200V.
EL Lamp Selection
EL lamps have a capacitance of approximately 2.5nF
to 3.5nF per square inch. See the Total Input Current
vs. Load graph in the
Typical Operating Characteristics
section for compatible lamp sizes.
Snubber Selection
An R
SN
value of 20Ω and C
SN
value of 330pF is suffi-
cient for V
DD
< 5V and C
LAMP_TOTAL
< 40nF. For higher
capacitive loads on the EL output or for V
DD
> 5V, C
SN
must be increased to keep LX spikes less than 30V.
f
SW
Selection
Choose a boost-converter frequency such that the sat-
uration current of the tapped-inductor primary coil is
not exceeded. Special attention must be given to pro-
gram the FSW bits properly when V
BAT
> 5.5V to avoid
destruction of the device. In general, it is good practice
to start from the highest f
SW
setting (1.6MHz) and
decrease accordingly to obtain the acquired wave-
shape on the EL outputs and to prevent exceeding the
saturation current of the tapped-inductor.
Applications Information
PCB Layout
Keep PCB traces as short as possible. Ensure that
bypass capacitors are as close to the device as possi-
ble. Use large ground planes where possible.
Chip Information
PROCESS: BiCMOS-DMOS
MAX14521E
Quad, High-Voltage EL Lamp Driver
with I
2
C Interface
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
20
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
24 TQFN-EP T2444M-1
21-0139
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages
.
*EXPOSED PAD. CONNECT EP TO GND.
I.C.
N.C.
N.C.
N.C.
N.C.EL1
N.C.
N.C.
N.C.
