PBL 380 85
July 1999
PBL 380 85
Integrated circuit for transformerless
driving of battery powered
EL (electroluminicent) lamps
Description.
PBL 380 85 is a monolithic integrated circuit for supplying power to an EL
(electroluminicent) lamp. This is intended to replace the LCD background illumination
system in battery powered handheld equipment with a low power EL- lamp. Especially
suitable for mobile phones where current saving is highly important, as background
illumination for both LCD and keyboard. Output voltage max. 190V, min. 170V at max.
2mA constant current charge / discharge of the EL- lamp. Application dependent
parameters such as charge / discharge current are set by an external resistor. Two control
signals are needed one for the switcher and one for the lamp.The output voltage is set
under 170V by the duty cycle and the switching frequency of the control signal, over 170V
by an amplitude limiter that switches the switcher off. The switching frequency is app. 50
kHz. The light intensity is controlled by the dutycycle of the switcher control signal. The
lamp control signal is divided by two by the circuit. The wave form of the output AC-signal
is either triangular or trapezoid depending of the capacitance of the EL-lamp, charge /
discharge current and frequency of the lamp control signal.The triangular or trapezoid
wave form of the EL-lamp driving voltage and the high switching frequency minimizes
audible noise from the lamp and also reduces upcoming electrical noise and harmonics.
Key features.
•
Minimum number of external
components for function: 1 choke, 1
filter-capacitor and 1 resistor.
Easy adaption to various lamp
specifications.
Easy dimming function by
controlling the duty cycle.
Extensive current saving feature
compared with LEDs.
Power down function <<1µA.
Supply voltage down to 3V.
Comes in a 3x3 mm package
Lights up to 20nF lamp capacitance
area depending on lamp
parameter nF/cm
2
.
•
•
•
•
•
•
•
+supply
5
10
9
switcher control
signal
2
EL-lamp
PBL 380 85
1
4
lamp control
signal
3
6
Pekka 11.11-98
PB
L
38
0
85
True size
10 - pin plastic mini SOP package
Functional diagram.
1
PB
L
38
8
0
85
ERICSSON [ ERICSSON ]
