The MAX4990 high-voltage DC-AC converter is ideal for
driving electroluminescent (EL) lamps. The MAX4990
features a wide +2.4V to +5.5V input range that allows
the device to accept a wide variety of voltage sources
such as single-cell lithium-ion (Li+) batteries and higher
voltage battery chargers. The lamp outputs of the
device generate up to 250V peak-to-peak output volt-
age for maximum lamp brightness.
The MAX4990 utilizes an inductor-based boost convert-
er to generate the high voltage necessary to drive an
EL lamp. The boost-converter switching frequency is
set with the combination of an external capacitor con-
nected from SW to GND and an external resistor con-
nected from SLEW to GND.
The MAX4990 uses a high-voltage full-bridge output
stage to convert the high voltage generated by the
boost converter to an AC waveform suitable for driving
the EL panel. The EL output switching frequency is set
with the combination of an external capacitor connect-
ed from EL to GND and an external resistor connected
from SLEW to GND.
The MAX4990 uses a proprietary acoustic noise-reduction
circuit that controls the slew rate of the AC voltage, reduc-
ing audible noise from the EL panel. The slew rate is set
with an external resistor connected from SLEW to GND.
The MAX4990 features an EL lamp dimming control
(DIM) that allows the user to set the EL output voltage
with a PWM signal, a DC analog voltage, or a resistor
connected from the DIM input to GND. A capacitor
placed in parallel to the resistor on DIM allows the user
to program a slow turn-on/-off time that generates a soft
fade-on/fade-off effect of the EL lamp.
The MAX4990 enters a low-power shutdown mode
(100nA max) when the EN and DIM inputs are connected
to GND. The MAX4990 also enters thermal shutdown
if the die temperature rises above +158°C.
The MAX4990 is available in a space-saving, 14-pin,
3mm x 3mm TDFN package and is specified over the
extended -40°C to +85°C operating temperature range.