General Description:
The Durel
Ò
D356B 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.
Data Sheet
D356B
Electroluminescent
Lamp Driver IC
B
D
6
35
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:
(Using Standard Test Circuit at Ta=25 °C unless otherwise specified.)
Parameter
Standby Current
Supply Current
Enable Current
Output Voltage
Lamp Frequency
Inductor Frequency
Symbol
I
Vout
LF
HF
Minimum
Typical
10
23
50
135
310
23
Maximum
100
30
75
220
390
Unit
nA
mA
uA
Vpp
Hz
kHz
Conditions
E = GND
E = 3.0V
E = 3.0V
CLF=5.0 nF
110
230
Standard Test Circuit
1
2
1.8mH
(3 Ohms)
GND
L-
VOUT
L+
D356B
E
CLF2
CLF1
V+
8
7
GND
OFF
3.0V
ON
5.0nF
3
4
6
5
0.1
m
H
Load B
3.0 Vdc
1
Load B*
47 nF
100
W
10k
W
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
VCLF
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 = V+
E = GND
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
1
2
3
4
8
7
6
5
1
2
3
4
5
6
7
8
GND
L-
VOUT
L+
V+
CLF1
CLF2
E
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
Note: Please consult factory for bare die dimensions and bond
pad locations.
2
Block Diagram of the Driver Circuitry
1.0
m
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 D356B 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 D356B Designer’s Kit, which includes a printed circuit evaluation board intended to aid you in
developing an EL lamp driver configuration using the D356B that meets your requirements. A section on designing
with the D356B is included in this datasheet to serve as a guide to help you select the appropriate external components
to complete your D356B EL driver system.
Typical D356B 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.
4
RF/Wirelessly
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