1
General Description:
The Durel
D371 is part of a family of highly integrated EL drivers
based on Durel's patented three-port (3P) topology, which offers
built-in EMI shielding. This high-performance device uses a
proprietary circuit design for programmable wave-shaping for low-
noise performance in applications that are sensitive to audible and
electrical noise.
Data Sheet
D371A
Electroluminescent
Lamp Driver IC
MSOP-10
Flexible Wave Shaping Capability
Cellular Phones and Handsets
High Efficiency
Data Organizers/PDAs
Small Package Size
LCD and Keypad Backlighting
Adjustable Output Frequency
High Voltage AC Output
External Clock Compatible
Features
Applications
Standard Test Circuit
nA
E = GND
mA
E = 3.0V
uA
E = 3.0V
Vpp
Hz
CLF=3.9 nF
kHz
CHF=68 pF
Parameter
Symbol
Minimum
Typical
Maximum
Unit
Conditions
(Using Standard Test Circuit at Ta=25 C unless otherwise specified.)
Lamp Driver Specifications:
Standby Current
5
1000
Supply Current
I
15
18
Enable Current
15
Output Voltage
Vout
160
188
220
Lamp Frequency
LF
190
260
330
Inductor Frequency
HF
23
D371A
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
Load A
3.9 nF
68 pF
D371A
+3.0 V
0.1
u
F
2.2 mH /
4 Ohms DCR
OFF
ON
GND
3.0V
2
Typical Output Waveform
Load A*
Physical Data:
PIN # NAME
FUNCTION
Absolute Maximum Ratings:
* Load A approximates a 3in
2
(19 cm
2
) EL lamp.
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.
Parameter
Symbol
Minimum
Maximum
Unit
Comments
Note: Please consult factory for bare die dimensions and bond
pad locations.
Supply voltage
Operating Range
V+
2.0
6.5
V
E = V+
Withstand Range
- 0.5
9.0
E = GND
Enable Voltage
E
- 0.5
(V+) +0.5
V
Output Voltage
V
OUT
220
Vpp
Peak-to-Peak Voltage
CHF Voltage
V
CHF
0
(V+) +0.3
V
External clock input
CLF Voltage
V
CLF
0
(V+) +0.3
V
External clock input
Operating Temperature
T
a
- 40
85
C
Storage Temperature
T
s
- 65
150
C
1
2
3
4
5
10
9
8
7
6
1
CHF
High frequency oscillator capacitor/clock input
2
CLF
Lamp frequency capacitor/clock input
3
E
System enable: Wave-shaping resistor control
4
DCH
Wave-shaping discharge control
5
GND
System ground connection
6
N/C
7
L-
Negative input to inductor
8
VOUT
High voltage AC output to lamp
9
L+
Positive input to inductor
10
V+
DC power supply input
100
10 nF
3
Output Voltage vs. DC Supply Voltage
0
40
80
120
160
200
240
2
3
4
5
6
7
DC Input Voltage
Output Voltage (Vpp)
Output Frequency vs. DC Supply
Voltage
0
50
100
150
200
250
300
350
400
2
3
4
5
6
7
DC Input Voltage
LF (Hz)
Supply Current vs. Ambient
Temperature
0
5
10
15
20
25
30
-40
-20
0
20
40
60
80
Temperature ( C)
Avg Supply Current (mA)
Output Voltage vs. Ambient
Temperature
0
40
80
120
160
200
240
-40
-20
0
20
40
60
80
Temperature ( C)
Output Voltage (Vpp)
Typical Performance Characteristics Using Standard Test Circuit
Supply Current vs. DC Supply Voltage
0
5
10
15
20
25
30
2
3
4
5
6
7
DC Input Voltage
Avg Supply Current (mA)
Output Frequency vs. Ambient
Temperature
0
50
100
150
200
250
300
350
400
-40
-20
0
20
40
60
80
Temperature ( C)
4
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.
Thus, Durel developed its patented Three-Port (3P) switch-mode driver circuit to convert the available DC supply to
an optimal drive signal for high brightness and low-noise EL lamp applications. The Durel 3P topology offers the
simplicity of a single DC input, single AC output, and a shared common ground that provides an integrated EMI
shielding.
The D371 drives the EL lamp by repeatedly pumping charge through an external inductor with current from a DC
source and discharging into the capacitance of the EL lamp load. With each high frequency (HF) cycle the voltage on
the lamp is increased. At a period specified by the lamp frequency (LF) oscillator, the voltage on the lamp is discharged
to ground and the polarity of the inductive charging is reversed. By this means, an alternating positive and negative
voltage is developed at the single output lead of the device to one of the electrodes of the EL lamp. The other lamp
electrode is commonly connected to a ground plane, which can then be considered as electrical shielding for any
underlying circuitry in the application.
The EL driving system is divided into several parts: on-chip logic and control, on-chip high voltage output circuitry,
discharge logic circuitry, and off-chip components. The on-chip logic controls the lamp operating frequency (LF), as
well as the inductor switching frequency (HF), and HF and LF duty cycles. These signals are combined and buffered
to regulate the high voltage output circuitry. The output circuitry handles the power through the inductor and delivers
the high voltage to the lamp. The integrated discharge logic circuit enables the low-noise functionality of this EL driver
with four levels of discharge slopes on the output waveform. The selection of off-chip components provides a degree
of flexibility to accommodate various lamp sizes, system voltages, and brightness levels. Since a key objective for EL
driver systems is to save space and cost, required off-chip components were kept to a minimum.
Durel provides a D371 Designer's Kit, which includes a printed circuit evaluation board intended to aid you in developing
an EL lamp driver configuration using the D371 that meets your requirements. A section on designing with the D371 is
included in this datasheet to serve as a guide to help you select the appropriate external components to complete your
D371 EL driver system.
Typical D371 configurations for driving EL lamps in various applications are shown on the following page. The
expected system outputs, such as lamp luminance, lamp output frequency and voltage, and average supply current
draw, for the various sample configurations are also shown with each respective figure.
Block Diagram of the Driver Circuitry
EL Lamp
E
V+
L+
L-
GND
VOUT
Low
Frequency
Oscillator
CLF
High
Frequency
Oscillator
1.0
F
CHF
Discharge
logic
Constant
current
discharge
R
enable
DCH
V
BAT
5
Typical D371 EL Driver Configurations
3.0V Handset LCD
Typical Output
Luminance= 5.0 fL (17 cd/m
2
)
Lamp Frequency = 330 Hz
Supply Current = 19 mA
Vout = 210 Vpp
Load = 1.5 in
2
(950 mm
2
) Durel 3 Green EL
5.0 V PDA
Typical Output
Luminance = 5.5 fL (19 cd/m
2
)
Lamp Frequency = 285 Hz
Supply Current = 15 mA
Vout = 200 Vpp
Load = 4 in
2
(2580 mm
2
) Durel 3 Green EL
3.3 V Handset LCD & Keypad
Typical Output
Luminance = 6.5 fL (22 cd/m
2
)
Lamp Frequency = 270 Hz
Supply Current = 15 mA
Vout = 190 Vpp
Load = 2.4 in
2
(1550 mm
2
) Durel 3 Green EL
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
4 in
2
EL Lamp
3.9 nF
Coilcraft DS1608BL
4.7 mH
100 pF
D371A
+5.0 V
1.0 u F
OFF
ON
GND
5.0V
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
2.4 in
2
EL Lamp
3.9 nF
Bujeon BDS3516S
2.2 mH
68 pF
D371A
+3.3 V
1.0 u F
OFF
ON
GND
3.3V
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
1.5 in
2
EL Lamp
3.3 nF
1.5mH Murata LQH3KS
68 pF
D371A
3.0V
1.0
F
82k
OFF
ON
GND
3.0V
6
Designing With D371A
I. Lamp Frequency Capacitor (CLF) Selection
Selecting the appropriate value of lamp frequency capacitor (CLF) for the low frequency oscillator will specify the
output frequency of the D371 EL driver. Lamp frequencies of 200-500Hz are typically used. Figure 1 graphically
represents the inversely proportional relationship between the CLF capacitor value and the oscillator frequency. In
this example at V+=3.0V, LF = 1150 nF-Hz/CLF.
Alternatively, the lamp frequency may also be controlled with an external clock signal with a typical duty cycle of 75%.
There is an internal frequency divider in the device so that the output lamp frequency will be half of the input clock
signal. For example, if a 500Hz input clock signal is used, the resulting lamp frequency will be 250Hz. The clock signal
input voltage should not exceed V+.
The selection of the CLF value can also affect the brightness of the EL lamp because of its control of the lamp frequency
(LF). Although input voltage and lamp size can change EL lamp frequency as well, LF mainly depends on the CLF
value selected or the frequency of the input clock signal to CLF. Figure 2 shows typical brightness of a D371 circuit with
respect to lamp frequency. In this example, the inductor and CHF values were kept constant while varying LF.
Figure 1: Typical Lamp Frequency vs. CLF Capacitor
Figure 2: Typical Lamp Luminance vs. Lamp Frequency
(V+ = 3.0V, 2.4 in
2
Durel 3 Green EL Lamp Load)
0
1
2
3
4
5
0
200
400
600
800
1000
Lamp Frequency (Hz)
Lamp Luminance (fL)
0
1
2
3
4
5
0
200
400
600
800
1000
Lamp Frequency (Hz)
Lamp Luminance (fL)
7
Selecting the appropriate value of capacitor for the high frequency oscillator (CHF) will set the inductor switching
frequency of the D371 IC. High inductor frequency allows for more efficient use of inductor coils with lower values.
However, care must be taken that the charge pumping does not reach a continuous mode at very high frequency when
the voltage is not efficiently transferred to the lamp load. Figure 3 graphically represents the effect of the CHF value
on the oscillator frequency at V+ = 3.0V.
II. High Frequency Capacitor (CHF) Selection
Figure 3: Typical Inductor Frequency vs. CHF Capacitor
The inductor switching frequency may also be controlled with an external clock signal. The inductor will charge
during the low portion of the clock signal and discharge into the EL lamp during the high portion of the clock signal.
The positive duty cycle used for the external high frequency clock signal is usually between 15%-75% with a typical
value of 15%-20% for maximum brightness. The clock signal input voltage should not exceed V+.
10
15
20
25
50
75 100 125 150 175 200 225
CHF (pF)
Inductor Frequency (kHz)
III. Inductor (L) Selection
The inductor value and inductor switching frequency have the greatest impact on the output brightness and current
consumption of the EL driver. Figures 4 and 5 show the dependence of brightness and current draw of a D371 circuit
on coil values and CHF values for two sample EL lamp sizes and input voltages. The CLF value was modified in each
case such that the output voltage was approximately 190Vpp. Please note that the DC resistance (DCR) of inductors
with the same nominal inductance value may vary with manufacturer and inductor type. Thus, inductors made by a
different manufacturer may yield different outputs, but the trend of the different curves should be similar.
8
Figure 4: Luminance and current vs. inductor and CHF value.
(Conditions: V+=3.0V, 2in
2
EL Lamp)
Figure 5: Luminance and current vs. inductor and CHF value.
(Conditions: V+=5.0V, 4in
2
EL Lamp)
0
2
4
6
8
10
12
0.4
0.5
0.6
0.7
0.8
1.0
1.2
1.5
1.8
2.2
2.7
3.3
3.9
Inductor (mH)
0
10
20
30
40
50
60
68 pF Luminance
100 pF Luminance
68 pF Current
100 pF Current
Luminance (fL)
Current (mA)
0
2
4
6
8
10
12
0.4
0.5
0.6
0.7
0.8
1.0
1.2
1.5
1.8
2.2
Inductor (mH)
0
10
20
30
40
50
60
68 pF Luminance
100 pF Luminance
68 pF Current
100 pF Current
Luminance (fL)
Current (mA)
IV. Wave-Shape Selection
The D371 driver IC uses a patented wave-shaping technique for reducing audible noise from an EL lamp. The linear
discharge of the output waveform may be adjusted by selecting one of 4 lamp discharge levels. The optimal discharge
level for an application depends on the lamp size, lamp brightness, and application conditions. To ensure that the D371
is configured optimally, each level should be evaluated. In many cases, the lower discharge levels result in lower
audible noise from the EL lamp.
9
Discharge level
Renable
DCH pin
Typical Lamp Size
1 (slowest)
80k
Open
0.1 - 2 in
2
2
0
Open
1.0 - 3.5 in
2
3
80k
GND
3.5 - 5 in
2
4 (fastest)
0
GND
>5 in
2
Typical waveshapes corresponding to the various discharge levels for a small size lamp and a larger size lamp are
shown below. In each case, the waveshape with the smoothest transition slopes in the discharge portion of the
waveform yields the lowest audible noise.
1in
2
EL Lamp
Discharge Level 1 (lowest noise)
Discharge Level 4
Discharge Level 4 (lowest noise)
8in
2
EL Lamp
Discharge Level 2
I. Driving Multiple EL Lamps
The D371 may be used to drive multiple EL lamp segments. An external transistor switching circuit is used to turn each lamp
segment on or off independently or simultaneously. A high signal at the corresponding E input will enable the corresponding
lamp segment. In this configuration, EL Lamp 1 is always turned on when the IC is enabled. Otherwise, always make sure
that at least one lamp segment is selected to be on when the D371 is enabled.
10
II. Two Level Dimming
Two level dimming may be achieved with the circuit below. When DIM is low, the external PNP transistor (2N3906 or
equivalent) is saturated and the EL lamp runs at full brightness. When DIM is high, the external PNP turns off and the
Rswitch resistor reduces the voltage at (V+) and dims the EL lamp.
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E1
DCH
GND
N/C
L-
Vout
L+
V+
D371A
Vbat
0.1 u F
OFF
ON
EL Lamp 2
EL Lamp 3
E2
2.2K
4.7K
BAS21LT1
BAS21LT1
MMBT5401LT1
MMBT5551LT1
1K
E3
2.2K
4.7K
BAS21LT1
BAS21LT1
MMBT5401LT1
MMBT5551LT1
1K
EL Lamp 1
100 nF
100 nF
OFF
ON
OFF
ON
OFF
ON
V
bat
R
switch
1k
DIM
2N3906
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
EL
Lamp
CLF
L
CHF
D371A
V
E
1.0 uF
R
enable
BRIGHT
DIM
3V
0V
D371 Design Ideas
III. Lamp Frequency Control with an External Clock Signal
An external clock signal may be used to control the EL lamp frequency (LF) of the D371A instead of using a capacitor.
There is an internal frequency divider in the IC so that the output lamp frequency will be half of the input clock signal.
For example, if a 500Hz input clock signal is used, the resulting lamp frequency will be 250Hz. The clock signal voltage
should not exceed V+. A typical duty cycle for the clock input is +75%, but it can also be adjusted within a range of 20%
to 99% to control brightness and discharge level. A higher positive duty cycle allows for longer charge time and peak
voltage, at the expense of a faster discharge slope and higher noise.
11
IV. EL Brightness Control Through HF Clock Pulse Width Modulation
The inductor oscillating frequency may also be controlled on the D371A EL driver IC using an external clock input to
CHF. In addition, pulse-width modulation of the external HF clock signal to the D371 may be used to regulate the
brightness of the EL lamp load. High frequency input is typically in the range of 10kHz to 40kHz, with duty cycle in the
range of 15% to 100%. In general, a lower HF frequency results in higher brightness and using a lower duty cycle
results in higher brightness. The clock signal voltage should not exceed V+. Prior to finalization of the circuit, contact
Durel to verify that the frequency, duty cycle, and setup chosen are acceptable for EL driver performance.
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
D371A
Vbat
0.1 u F
OFF
ON
EL Lamp
1.0V Min
0.2V Max
200Hz - 2KHz
20%-99% +Duty
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
D371A
Vbat
0.1 uF
OFF
ON
EL Lamp
1.0V Min
0.2V Max
10KHz - 40KHz
15%-100% Duty
12
V. EL Lamp Brightness Regulation
Regulating the DC supply input voltage to the D371 will result in a constant brightness level from the EL lamp,
regardless of battery voltage. In this example, a Micrel voltage regulator is used.
VI. Output Voltage Limiting
An EL driver system using the D371 driver IC should be designed such that the output voltage does not exceed the
maximum rated value of 220Vpp. A pair of zener diodes connected to the output as shown below is recommended to
limit Vout to within 200Vpp or less. This circuit protects the device from over-voltage when typical performance is near
the maximum limit for the D371.
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
EL
Lamp
CLF
L
CHF
D371A
V
BAT
1.0 uF
R
enable
1N5271 or
equivalent
100V zener
diodes
OFF
ON
1
2
3
4
5
6
7
8
9
10
CHF
CLF
E
DCH
GND
N/C
L-
Vout
L+
V+
D371A
0.1 u
F
OFF
ON
EL Lamp
Vbat
1 GND
2 E
OUT
IN
4
3
MIC5203
E
13
D371A Application Testing Recommendations
The following recommendations should be considered when testing the D371A device to ensure that the devices are
not damaged.
1) Do not perform any no load test. If no load test is required, please contact Durel Corporation on proper test
procedure.
2) Place 100V Zener diodes on the Vout pin to ground to prevent exceeding the maximum rated output (220Vpp).
Zener diodes will clamp output voltage to 200Vpp. See diagram below.
3) It has been found that DC transient voltages applied to the Vout pin of the D371A while in operation can cause
internal damage. Built up charge can sometimes be found on an EL Lamp or dummy load test fixture. This built up
charge can act as a DC transient. Place a high value resistor (value depending on RC time constant) in parallel with
EL lamp or dummy load to allow built up charge to discharge properly. See diagram below.
CHF
CLF
E
DCH
GND
V+
L+
Vout
L-
N/C
D371A
EL Lamp or
Dummy Load
V
DD
V
DD
100 V Zener
100 V Zener
1 Mohm
or greater
The DUREL name and logo are registered trademarks of DUREL CORPORATION.
This information is not intended to and does not create any warranties, express or implied, including any warranty of merchantability or fitness for a
particular purpose. The relative merits of materials for a specific application should be determined by your evaluation.
The EL driver circuits herein are covered by one or more of the following patents: #5,313,141; #5,347,198; #5,789,870.; 6,259,619. Corresponding foreign
patents are issued and pending.
A
0.92
0.036
1.00
0.039
1.08
0.043
B
0.05
0.002
0.10
0.004
0.15
0.006
C
0.15
0.006
0.23
0.009
0.31
0.012
D
0.40
0.016
0.55
0.022
0.70
0.028
E
0.13
0.005
0.18
0.007
0.23
0.009
F
2.90
0.114
3.00
0.118
3.10
0.122
G
0.35
0.014
0.50
0.020
0.65
0.026
H
4.75
0.187
4.90
0.193
5.05
0.199
I
2.90
0.114
3.00
0.118
3.10
0.122
Description
mm.
in.
mm.
in.
mm.
in.
MSOP-10
Min.
Typical
Max.
The D371A IC is available as bare die in probed wafer form or in die tray, and in standard MSOP-10 plastic package per
tape and reel. A Durel D371 Designer's Kit (1DDD371AA-K01) provides a vehicle for evaluating and identifying the
optimum component values for any particular application using D371. Durel engineers also provide full support to
customers, including specialized circuit optimization and application retrofits.
MSOPs in Tape and Reel:
1DDD371AA-M04
RECOMMENDED PAD LAYOUT
DUREL Corporation
2225 W. Chandler Blvd.
Chandler, AZ 85224-6155
Tel: (480) 917-6000
FAX: (480) 917-6049
Website: http://www.durel.com
2000, 2001 Durel Corporation
Printed in U.S.A.
LIT-I9028 Rev. A10
ISO 9001 Certified
Ordering Information
MSOPs are marked with part number (371A) and 3-digit wafer lot
code. Bottom of marking is on the Pin 1 side.
Embossed tape on 360 mm diameter reel per EIA-481-2.
2500 units per reel. Quantity marked on reel label.
F
H
I
A
B
G
C
D
E
Tape Orientation
e
c
a
b
d
f
mm.
in.
mm.
in.
mm.
in.
Min.
Typical
Max.
MSOP-10 PAD LAYOUT
a
0.5
0.0197
b
2.0
0.0788
c
3.3
0.130
3.45
0.136
d
0.89
0.035
0.97
0.038
1.05
0.041
e
5.26
0.207
5.41
0.213
f
0.3
0.012
PDF 
ZIP