Data Sheet
D355B
Electroluminescent
Lamp Driver IC
General Description
The Durel
®
D355B 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 efficiency
device is well suited for backlighting most timepieces and
liquid crystal displays for portable electronic applications.
D
5
35
B
MSOP-8
Features
•
•
•
•
•
High Efficiency
Low Voltage Operation
Small System Footprint
Controlled Current Discharge for Low EMI
Capacitor or External Clock LF Control
•
•
•
•
Applications
Watches
Data Organizers/PDAs
Pagers
LCD and Keypad Backlighting
Lamp Driver Specifications
Parameter
Standby Current
Supply Current
Enable Current
Output Voltage
Lamp Frequency
Inductor Frequency
(Using Standard Test Circuit at Ta=25 °C unless otherwise specified.)
Symbol
I
Vout
LF
HF
Minimum
Typical
10
23
-10
145
310
23
Maximum
1000
30
-35
220
390
Unit
nA
mA
µA
Vpp
Hz
kHz
Conditions
E’ = 3.0V
E’ = GND
E’ = GND
E’ = GND
CLF = 5.0nF
110
230
Standard Test Circuit
1 GND
2 L-
1.8mH
(3 Ohms)
E’ 8
CLF2 7
E’
ON
GND
OFF
3.0V
5.0nF
3 VOUT
4 L+
D355B
CLF1 6
V+ 5
0.1
µ
F
3.0 Vdc
Load B
1
Load B*
47 nF
100Ω
10kΩ
22 nF
Typical Output Waveform
* Load B approximates a 5in
2
EL lamp.
Absolute Maximum Ratings
Parameter
Supply voltage
Operating range
Withstand range
Enable Voltage
Output Voltage
CLF Voltage
Operating temperature
Storage temperature
Symbol
V+
E’
Vout
V
CLF
T
a
T
s
Minimum
1.0
-0.5
-0.5
0
-40
-65
Maximum
7.0
10.0
(V+) +0.5
220
(V+)+0.3
85
150
Unit
V
V
Vpp
V
°C
°C
Comments
E’ = GND
E’ = V+
Peak to peak voltage
External clock input
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
FUNCTION
System ground connection
Negative input to inductor
High voltage AC output to lamp
Positive input to inductor
DC power supply input
Lamp frequency capacitor/clock input
Lamp frequency capacitor/clock input
System enable; Power Down Control
1
2
3
4
8
7
6
5
1
2
3
4
5
6
7
8
GND
L-
Vout
L+
V+
CLF1
CLF2
E’
Note: Please consult factory for bare die physical data
and bond pad locations
2
Block Diagram of the Driver Circuitry
1.0
µ
F
E’
V+
L+
CLF1
CLF2
Low
Frequency
Oscillator
High
Frequency
Oscillator
L-
VOUT
GND
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. Thus, Durel developed its patented Three-Port (3P) switch-mode inverter 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 D355B 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 on 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 output 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 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 D355B Designer’s Kit, which includes a printed circuit evaluation board intended to aid
you in developing an EL lamp driver configuration using the D355B that meets your requirements. A section
on designing with the D355B is included in this datasheet to serve as a guide to help you select the appropriate
external components to complete your D355B EL driver system.
Typical D355B 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.
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