General Description:
The Durel® D372A is designed to drive EL lamps with a regulated
high-voltage signal. This driver IC uses a proprietary circuit design
for programmable wave-shaping for low-noise performance in
applications that are sensitive to audible and electrical noise, such
as cellular phones and handsets.
Data Sheet
D372A
Electroluminescent
Lamp Driver IC
MSOP-10
Features
•
•
•
•
•
Regulated High AC Voltage Output
Adjustable Output Frequency
Flexible Wave-Shaping Capability
Small Package Size
External Clock Compatible
Applications
•
Cellular Phones and Handsets
•
Data Organizers/PDAs
•
LCD Backlighting
Lamp Driver Specifications:
(Using Standard Test Circuit at Ta=25 °C unless otherwise specified.)
Parameter
Standby Current
Supply Current
Enable Current
On
Off
Output Voltage
Lamp Frequency
Inductor Frequency
Symbol
I
Minimum
Typical
5
21
15
Maximum
1000
28
50
20
220
330
24
Unit
nA
mA
µA
nA
Vpp
Hz
kHz
D3
72
A
Conditions
E = GND
E = 3.3V
E = 3.3V
E = GND
Vout
LF
HF
160
190
14
188
260
18
Standard Test Circuit
820
Ω
+3.3 V
2.0 nF
.1
µF
1 V+
2 CLF
3 CHF
Rd 10
EL2 9
Load A
EL1 8
47 nF
ON
OFF
68 pF
4 E
5 GND
D372A
Cs 7
L+ 6
2.2 mH
DCR = 2Ω
+3.3 V
1
Load A*
Sample Output Waveform
100
Ω
10 nF
* Load A approximates a 3in
2
EL lamp.
Absolute Maximum Ratings:
Parameter
Supply voltage
Operating range
Withstand range
Enable Voltage
Lamp Output
Operating temperature
Storage temperature
Symbol
V+
E
Vout
T
a
T
s
Minimum
2.0
-0.5
-0.5
-40
-65
Maximum
6.5
9.0
(V+) +0.5
220
85
150
Unit
V
V
Vpp
°C
°C
Comments
E = V+
E = GND
E = V+
Note: The above are stress ratings only. Functional operation of the device at these ratings or any other above
those indicated in the specifications is not implied. Exposure to absolute maximum rating conditions for extended
periods of time may affect reliability.
Physical Data:
PIN # NAME
1
10
2
9
FUNCTION
DC power supply input
Low frequency oscillator capacitor/LF clock input
High frequency oscillator capacitor/HF clock input
System enable: HI = On
System ground connection
Charge pumping inductor input
High voltage storage capacitor
AC output to lamp
AC output to lamp
Wave shaping resistor
3
8
4
7
5
6
1
2
3
4
5
6
7
8
9
10
V+
CLF
CHF
E
GND
L+
Cs
EL1
EL2
Rd
2
Typical Performance Characteristics Using Standard Test Circuit
400
350
300
LF (Hz)
400
350
300
250
200
150
100
50
0
-40
-20
0
20
Temperature ( C)
o
LF (Hz)
250
200
150
100
50
0
1
2
3
4
5
6
7
40
60
80
DC Input Voltage
Output Frequency vs. DC Supply Voltage
Output Frequency vs. Ambient Temperature
300
Output Voltage (Vpp)
300
Ouput Voltage (Vpp)
250
200
150
100
50
0
1
2
3
4
5
6
7
DC Input Voltage
250
200
150
100
50
0
-40
-20
0
20
Temperature (
o
C)
40
60
80
Output Frequency vs. DC Supply Voltage
Output Frequency vs. Ambient Temperature
25
Avg Supply Current (mA)
Avg Supply Current (mA)
25
20
15
10
5
0
20
15
10
5
0
1
2
3
4
DC Input Voltage
5
6
7
-40
-20
0
20
Temperature (
o
C)
40
60
80
Output Frequency vs. DC Supply Voltage
Output Frequency vs. Ambient Temperature
3
Block Diagram of the Driver Circuitry
V
BAT
E
V+
L+
C
S
CHF
High
Frequency
Oscillator
L
o
g
i
c
L
o
g
i
c
CLF
Low
Frequency
Oscillator
Divide
by 2
R
d
GND
EL1
EL2
EL Lamp
Theory of Operation
Electroluminescent (EL) lamps are essentially capacitors with one transparent electrode and a special phosphor material
in the dielectric. When a strong AC voltage is applied across the EL lamp electrodes, the phosphor glows. The
required AC voltage is typically not present in most systems and must be generated from a low voltage DC source.
The D372 chip inverter drives the EL lamp by using a switching BJT to repeatedly charge an external inductor and
discharge it to the high voltage capacitor Cs. The discharging causes the voltage at Cs to continually increase. When
the voltage at Cs reaches a nominal value, the switching BJT is turned off. The internal circuitry uses the H-bridge
technology, using both electrodes to drive the EL lamp. One of the outputs, EL1 or EL2, is used to discharge Cs into the
EL lamp during the first half of the low frequency (LF) cycle. By alternating the state of the H-bridge, the other output
is used to charge the EL lamp during the second half of the LF cycle. The alternating states make it possible to achieve
200V peak-to-peak across the EL lamp.
The EL driving system is divided into several parts: on-chip logic control, on-chip high voltage output circuitry, on-chip
discharge logic circuitry, and off-chip components. The on-chip logic controls the lamp operating frequency (LF) and
the inductor switching frequency (HF). These signals are used to drive the high voltage output circuitry (H-bridge) by
delivering the power from the inductor to the lamp. The integrated discharge logic circuitry uses a patented wave
shaping technique for reducing audible noise from an EL lamp. Changing the Rd value changes the slope of the linear
discharge as well as the shape of the waveform. The off-chip component selection provides a degree of flexibility to
accommodate various lamp sizes, system voltages, and brightness levels.
Typical D372 EL driving configurations for driving EL lamps in various applications are shown on the following page.
The expected system outputs for the various circuit configurations are also shown with each respective figure. These
’
examples are only guides for configuring the driver. Durel provides a D372 Designers Kit, which includes a printed
circuit evaluation board intended to aid you in developing an EL lamp driver configuration using the D372 that meets
your requirements. A section on designing with the D372 is included in this datasheet to serve as a guide to help you
select the appropriate external components to complete your D372 EL driver system.
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