MIC4827
EL Frequency
The EL lamp frequency is controlled via an external resistor
connected between REL pin and VDD pin of the device. The
lamp frequency increases the resistor value decreases. For
resistor value selections, see the “Typical Characteristics: EL
Frequency vs. EL Resistor” or use the equation below. The
switching frequency range is 60Hz to 1000Hz, with an accu-
racy of
±20%.
f
EL
(Hz)
=
360
R
EL
(M
Ω
)
Micrel
In general, as the EL lamp frequency increases, the amount
of current drawn from the battery will increase. The color of
the EL lamp and the intensity are dependent upon its fre-
quency.
V
A
(50V/div)
V
B
(50V/div)
V
IN
= 3.0V
L = 220µH
C
OUT
= 0.033µF
Lamp = 2in
2
R
SW
= 562k
R
EL
= 1M
V
A
— V
B
(50V/div)
V
B
(50V/div)
V
A
(50V/div)
TIME (2ms/div)
Figure 4. 360Hz Output Waveform
V
A
— V
B
(50V/div)
Enable Function
The enable function of the MIC4827 is implemented by
switching the R
SW
and R
EL
resistor between ground and V
DD
.
When R
SW
and R
EL
are connected to ground, the switch and
the EL oscillators are disabled; therefore the EL driver be-
comes disabled. When these resistors connect to V
DD
, both
the oscillators will function and the EL driver is enabled.
TIME (2ms/div)
Figure 3. 180Hz Output Waveform
January 2005
7
MIC4827
MICREL [ MICREL SEMICONDUCTOR ]
