MAX4990E Maxim Integrated Products, MAX4990E Datasheet - Page 10

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

As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static discharges encountered during handling and
assembly. The EL lamp driver outputs of the MAX4990E
have extra protection against static electricity. Maxim’s
engineers have developed state-of-the-art structures to
protect these pins against ESD of ±15kV without dam-
age. The ESD structures withstand high ESD in all
states: normal operation, shutdown, and powered
down. After an ESD event, the MAX4990E keep working
without latchup or damage.
ESD protection can be tested in various ways. The
transmitter EL lamp outputs of the MAX4990E are char-
acterized for protection to the following limits:
•
•
•
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents
test setup, test methodology, and test results.
Figure 1a shows the Human Body Model, and Figure
1b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter-
est, which is then discharged into the test device
through a 1.5kΩ resistor.
The IEC 61000-4-2 standard covers ESD testing and
performance of finished equipment. However, it does
not specifically refer to integrated circuits. The
MAX4990E assists in designing equipment to meet IEC
61000-4-2 without the need for additional ESD-protec-
tion components.
The major difference between tests done using the
Human Body Model and IEC 61000-4-2 is higher peak
current in IEC 61000-4-2 because series resistance is
lower in the IEC 61000-4-2 model. Hence, the ESD
withstand voltage measured to IEC 61000-4-2 is gener-
ally lower than that measured using the Human Body
Model. Figure 1c shows the IEC 61000-4-2 model, and
Figure 1d shows the current waveform for IEC 61000-4-
2 ESD Contact Discharge test.
High-Voltage, ±15kV ESD-Protected
Electroluminescent Lamp Driver
10
±15kV using the Human Body Model
±4kV IEC 61000-4-2 Contact Discharge
±15kV IEC 61000-4-2 Air-Gap Discharge
______________________________________________________________________________________
±15kV ESD Protection
ESD Test Conditions
Human Body Model
IEC 61000-4-2
The machine model for ESD tests all pins using a 200pF
storage capacitor and zero discharge resistance.
The objective is to emulate the stress caused when I/O
pins are contacted by handling equipment during test
and assembly. Of course, all pins require this protection.
The Air-Gap test involves approaching the device with a
charged probe. The Contact Discharge method connects
the probe to the device before the probe is energized.
The recommended inductor values are 220µH/330µH.
For most applications, series resistance (DCR) should
be below 8Ω for reasonable efficiency. Do not exceed
the inductor’s saturation current.
To help reduce audible noise emission by the EL lamp,
the MAX4990E features a slew-rate control input
(SLEW) that allows the user to set the slew-rate of the
high-voltage outputs, V
resistor, R
precisely sets the reference current I
charge and discharge the capacitances at the SW
input and EL input, and is used as a reference current
for internal circuitry. The reference current is related to
R
Decreasing the value of R
increases the slew rate at the EL lamp output. Increasing
the value of R
slew rate at the EL lamp output. The output slew rate is
related to R
The ideal value for a given design varies depending on
lamp size and mechanical enclosure. Typically, the best
slew rate for minimizing audible noise is between
10V/100µs and 20V/100µs. This results in R
ranging from 1.125MΩ to 0.5625MΩ. For example, if the
desired slew rate is 20 (V/100µs), this leads to an R
resistor value in MΩ of R
Note: Connecting R
device. However, for the device to operate correctly,
R
R
(see the C
EL lamp (see the C
the peak-to-peak voltage of the EL lamp.
SLEW
SLEW
SLEW
should be in the 100kΩ to 2.2MΩ range.
also affects the frequency of the boost converter
by the following equation: I
SlewRate
SLEW
SW
SLEW
Capacitor Selection ), the frequency of the
SLEW
, from the SLEW input to GND. R
by the following equation:
EL
⎛
⎜
⎝
SLEW
100
decreases I
Capacitor Selection section), and
R
V
SLEW
SLEW
μ
s
A
to GND will not damage the
⎞
⎟ =
⎠
Design Procedure
L
and V
X
= 11.25/20V = 0.5625MΩ.
SLEW
R
Inductor Selection
Resistor Selection
SLEW
B
www.DataSheet4U.com
1
B,
1 25
and decreases the
Machine Model
.
increases I
by connecting a
( )
M
B
B
Ω
that is used to
= 1V/R
SLEW
B
values
SLEW
SLEW
SLEW
and
.