Micrel, Inc.
MIC4827
V
IN
= 3.0V
L = 220µH
C
OUT
= 0.033µF
2
Lamp = 2in
R
SW
= 332k
R
EL
= 3.32M
V
A
V
B
(50V/div) (50V/div)
V
B
V
A
(50V/div) (50V/div)
V
IN
= 3.0V
L = 220µH
C
OUT
= 0.033µF
2
Lamp = 2in
R
SW
= 562k
R
EL
= 1M
TIME (2ms/div)
V
A
— V
B
(50V/div)
V
A—
V
B
(50V/div)
TIME (2ms/div)
Figure 2. 108Hz Typical Output Waveform
Figure 3. 180Hz Output Waveform
f
SW
(kHz)
=
36
R
SW
(
M
Ω
)
EL Frequency
The EL lamp frequency is controlled via an external
resistor connected between R
EL
pin and V
DD
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 accuracy of ±20%.
f
EL
(
Hz
)
360
R
EL
(
M
Ω
)
V
A
— V
B
(50V/div)
V
A
V
B
(50V/div) (50V/div)
Switching Frequency
The switching frequency of the converter is controlled via
an external resistor between R
SW
pin and V
DD
pin of the
device. The switching frequency increases as the
resistor value decreases. For resistor value selections,
see the “Typical Characteristics: Switching Frequency
vs. Switch Resistor” or use the equation below. The
switching frequency range is 8kHz to 200kHz, with an
accuracy of ±20%.
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 frequency.
TIME (2ms/div)
Figure 4. 360Hz Output Waveform
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 becomes disabled. When these resistors
connect to V
DD
, both the oscillators will function and the
EL driver is enabled.
July 2009
8
M9999-070709-A
(408) 955-1690
MICREL [ MICREL SEMICONDUCTOR ]
