MAX4990E Maxim Integrated Products, MAX4990E Datasheet - Page 9

• Manufacturer Part Number: MAX4990E
• Description: High-Voltage +-15kV ESD-Protected Electroluminescent Lamp Driver
• Manufacturer: Maxim Integrated Products

Increasing the voltage on the DIM input increases the
peak-to-peak voltage, and decreasing the voltage on
the input decreases the peak-to-peak voltage. The EL
lamp peak-to-peak voltage is also adjusted by applying
a PWM signal to the DIM input. The duty cycle of the
PWM determines the EL lamp output peak-to-peak volt-
age. As the duty cycle is increased, the peak-to-peak
output voltage is increased, and as the duty cycle is
decreased, the peak-to-peak voltage is decreased. The
MAX4990E also features a slow turn-on and slow turn-off
time feature that is enabled by connecting a resistor and
capacitor from DIM to GND (see the Typical Application
Circuits and the R
Selection section). This slow turn-on/-off feature causes
the peak-to-peak voltage of the EL outputs to slowly rise
from zero to the maximum set value when the device is
enabled. This feature also causes the peak-to-peak volt-
age of the EL outputs to fall from the maximum set value
to zero when the device is placed into shutdown. The
slow rise and fall of the peak-to-peak EL output voltage
creates a soft fade-on and fade-off of the EL lamp,
rather than an abrupt change in brightness.
The MAX4990E boost converter consists of an external
inductor from V
switch, an external diode from LX to the CS output, an
external capacitor from the CS output to GND, and the
EL lamp, C
When the DMOS switch is turned on, LX is connected
to GND, and the inductor is charged. When the DMOS
switch is turned off, the energy stored in the inductor is
transferred to the capacitor C
Note: Keeping SW high shorts LX to GND, causing the
internal die temperature to increase. The MAX4990E is
protected by entering a thermal-shutdown state (See
the Thermal Short-Circuit Protection section.)
The MAX4990E boost converter frequency uses an
internal switch oscillator to set the desired frequency of
the boost converter. The boost converter frequency is
adjusted by either 1) the combination of a resistor from
SLEW to GND and an external capacitor from SW to
GND, or 2) by driving a PWM signal directly into the SW
input. When SW is driven with an external PWM signal
at a suggested 90% duty cycle, the boost converter fre-
quency is changed to the frequency of the external
PWM signal. (See the C
for choosing the C
The MAX4990E features a dimming control input, DIM,
that controls the peak-to-peak voltage on the lamp out-
puts V
A
and V
LAMP
B
DD
. DIM is controlled by a resistor con-
, connected to the EL lamp outputs.
_______________________________________________________________________________________
SW
DIM
to the LX input, an internal DMOS
capacitor value.)
SW
Resistor and C
Capacitor Selection section
CS
and the EL lamp.
High-Voltage, ±15kV ESD-Protected
Dimming Control
Boost Converter
DIM
Electroluminescent Lamp Driver
Capacitor
nected from the DIM input to GND, a PWM signal
applied to the DIM input, or a DC voltage applied to the
DIM input. (See the R
Selection section.)
The duty cycle of a PWM signal to the DIM input is
internally translated into a DC voltage with the 0 to
+1.22V range. The DIM input accepts the frequency
range of 200kHz to 1MHz. As the duty cycle increases,
the peak-to-peak voltage of the output increases, and
as the duty cycle decreases, the peak-to-peak voltage
of the output decreases.
The peak-to-peak voltage is adjusted by applying a DC
voltage to the DIM input. Increasing the voltage on DIM
increases the peak-to-peak output, and decreasing the
voltage on DIM decreases the peak-to-peak output
voltage.
The DIM input, in combination with the EN input, con-
trols the shutdown mode of the MAX4990E shutdown.
(See the Shutdown section.)
The MAX4990E provides a slow turn-on/-off feature by
connecting a resistor in parallel with a capacitor con-
nected from the DIM input to GND (see the R
Resistor and C
EN is driven high, the reference current I
R
driven to GND, I
capacitor C
stant of R
driving EN high. The slow rise and fall of the voltage on
DIM during transitions on the EN input modulates the
peak-to-peak voltage of the EL outputs, creating a soft
fade-on/-off effect at the EL lamp.
The MAX4990E features an enable logic input, EN, to
enable and disable the device. To enable the device,
apply +1.2V or greater to the EN input and +0.35V or
greater to the DIM input. To place the device in shut-
down, apply +0.2V or less to the EN input, and +0.15V
or less to the DIM input.
The MAX4990E has a UVLO threshold of +2.1V (typ).
When V
nonoperative mode.
The MAX4990E enters a nonoperative mode if the inter-
nal die temperature of the device reaches or exceeds
+158°C (typ). The device turns back on when the inter-
nal die temperature cools to +150°C.
SLEW
) is used to charge capacitor C
DD
DIM
falls below +2.1V (typ), the device enters a
DIM
Thermal Short-Circuit Protection
x C
DIM
and resistor decays with a time con-
B
Undervoltage Lockout (UVL0)
DIM
Slow Turn-On, Slow Turn-Off
is removed, and the voltage on the
Capacitor Selection section). When
. A slow turn-on effect is seen by
DIM
Resistor and C
www.DataSheet4U.com
DIM
DIM
. When EN is
Shutdown
B
Capacitor
(set by
DIM
9