Datasheet

Detailed Description
The MAX4990 high-voltage DC-AC converter is ideal
for driving 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 sin-
gle cell Li+ batteries and higher voltage battery charg-
ers. The lamp outputs of the device generate up to
250V peak-to-peak output voltage for maximum lamp
brightness.
The MAX4990 utilizes an inductor-based boost convert-
er that allows for the use of a 220µH inductor to gener-
ate the high voltage necessary to drive an EL lamp. The
boost converter switching frequency is set with the
combination of an external capacitor connected from
the SW input to GND and an external resistor connected
from SLEW to GND. Applying a PWM signal to the SW
input allows the switching frequency of the boost con-
verter to take the frequency of the PWM signal.
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 allows programma-
bility of the EL Lamp output frequency by applying a
clock signal to the EL input. Applying a clock signal to
the EL input allows the switching frequency of the lamp
to take the frequency of the clock signal divided by 4 to
switch at the EL input frequency divided by 4.
The MAX4990 uses a proprietary acoustic noise-reduc-
tion circuit to control the slew rate of the AC voltage,
reducing audible noise from the EL panel. The slew rate
is set with an external resistor connected from SLEW to
GND.
The MAX4990 enters a low-power shutdown mode
(100nA max) when EN and DIM inputs are connected
MAX4990
High-Voltage, ±15kV ESD-Protected
Electroluminescent Lamp Driver
_______________________________________________________________________________________ 7
Pin Description
PIN NAME FUNCTION
1 SLEW
High-Voltage Slew-Rate Control. Connect an external resistor, R
SLEW
, to GND to set the slew rate of
the V
A
and V
B
high-voltage outputs.
2EN
Enable Input. Drive EN > +1.2V and DIM > +0.35V to turn on the device. Drive EN < +0.2V and DIM <
+0.15V to turn off the device.
3 DIM
EL Panel Dimming Control. Apply a PWM signal or DC analog control signal, or connect a resistor to
GND to adjust peak-to-peak output voltage. Use DIM together with EN to control device shutdown
(see Shutdown section).
4EL
EL Voltage Switching Frequency. Connect an external capacitor, C
EL
, to GND or drive with an external
oscillator to set the switching frequency of the V
A
and V
B
high-voltage outputs. Connect EL to GND to
shut off the EL oscillator. Drive EL high to keep alternatively V
A
or V
B
output high.
5SW
Boost-Converter Switching Frequency. Connect an external capacitor, C
SW
, to GND or drive with an
external oscillator to set the switching frequency of the boost converter. Connect SW to GND to shut
off the boost oscillator. Do not keep SW high to avoid LX shorting to GND, which causes the internal
die temperature to increase. The MAX4990 is protected by entering a themal-shutdown state. (See the
Thermal Short-Circuit Protection section.)
6V
DD
Power-Supply Voltage
7 GND Ground
8LX
Internal Switching DMOS Drain Connection. Connect LX to a switching inductor and an anode of a
rectifying diode.
9, 11, 13 N.C. No Connection. Leave N.C. unconnected.
10 CS High-Voltage Supply. Connect CS to output capacitor of boost converter.
12 V
B
High-Voltage EL Panel Output. Connect to non-V
A
side of EL lamp.
14 V
A
High-Voltage EL Panel Output. Connect to non-V
B
side of EL lamp.
EP EP Exposed Pad. Connect exposed pad to GND.