Datasheet

MAX4990
to GND. The MAX4990 also enters thermal shutdown if
the die temperature rises above +158°C.
The MAX4990 features an EL lamp dimming control
(DIM) that allows the user to set the EL output voltage
with a PWM, DC analog voltage, or a resistor connect-
ed to GND. A capacitor placed in parallel to the resistor
on the DIM input allows the user to program a slow
turn-on/-off time of the MAX4990’s outputs to generate
a soft fade-on/fade-off effect of the EL lamp.
The high-voltage outputs are ESD protected up to
±15kV Human Body Model, ±15kV Air-Gap Discharge,
and ±4kV Contact Discharge, as specified in the IEC
61000-4-2 specification.
EL Output Voltage
The slew rate, frequency, and peak-to-peak voltage of the
MAX4990 EL lamp outputs are programmed through a
combination of external components and/or DC inputs.
The device uses resistor R
SLEW
to set the bias current
used as a reference current for the MAX4990 internal
circuitry. The reference current directly affects the slew
rate of the EL lamp output. Increasing the value of
R
SLEW
decreases the slew rate, and decreasing the
value of R
SLEW
increases the slew rate. (See the R
SLEW
Resistor Selection section on how to select R
SLEW
.)
The MAX4990 EL lamp output frequency uses an inter-
nal EL oscillator to set the desired frequency. The out-
put frequency is adjusted by either 1) the combination
of a resistor from SLEW to GND and an external capaci-
tor from the EL input to GND, or 2) by driving a clock
signal directly into the EL input. (See the C
EL
Capacitor
Selection section for choosing the C
EL
capacitor value.)
The peak-to-peak voltage of the EL lamp output is var-
ied from 70V
P-P
to 250V
P-P
by applying an external DC
voltage ranging from +0.35V to +1.3V to the DIM input.
High-Voltage, ±15kV ESD-Protected
Electroluminescent Lamp Driver
8 _______________________________________________________________________________________
+-
-+
SWITCH
OSCILLATOR
V
DD
SW
LX
CS
V
A
V
B
EL
SLEW
EN
DIM
GND
TIMEOUT
EL
OSCILLATOR
V-I
CONVERTER
HIGH ESD
PROTECTION
H-BRIDGE
HIGH ESD
PROTECTION
DMOS
DRIVER
REF
N
V
SENSE
LOW-POWER
SHUTDOWN
LOW PEAK
DETECTOR
LOW-POWER
SHUTDOWN
SHUTDOWN
NO-OPERATION
SIGNAL
TIMEOUT
PWM
CONVERTER
THERMAL
SHUTDOWN
UVLO
MAX4990
Functional Diagram