Micrel
MIC4830
VA
(50V/div)
I
IN
= 12mA
L = 220µH
C
OUT
= 2.7nF
LAMP = 2 in
2
R
SW
= 250k
VA
(50V/div)
V
IN
= 3.6V
V
IN
= 3.6V
I
IN
= 19mA
L = 220µH
C
OUT
= 2.7nF
LAMP = 2 in
2
R
SW
= 290k
VB
(50V/div)
VA - VB
(100V/div)
Time (2ms/div)
VA - VB
(100V/div)
VB
(50V/div)
R
EL
= 2.82M
R
EL
= 1.69M
Time (2ms/div)
Figure 2. 100Hz Output Waveform
Figure 3. 200Hz Output Waveform
f
SW
(kHz)
=
36
R
SW
(
M
Ω
)
VA - VB
(100V/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. SW
Resistor” or use the equation below. The switching
frequency range is 65kHz to 250kHz, with an
accuracy of ±20%.
In general, the lower the
switching frequency, the greater the input current is
drawn to deliver more power to the output.
However, the switching frequency should not be so
low as to allow the voltage at the switch node or the
CS pin to go beyond the absolute maximum voltage
of those pins.
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.
VA
(50V/div)
V
IN
= 3.6V
I
IN
= 25mA
L = 220µH
C
OUT
= 2.7nF
LAMP = 2 in
2
R
SW
= 352k
VB
(50V/div)
R
EL
= 1.1M
Time (2ms/div)
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 as the
resistor value decreases. For resistor value
selections, see the “Typical Characteristics: EL
Frequency vs. EL Resistor” graph on page 4 or use
the equation below. The EL lamp frequency range is
60Hz to 1000Hz, with an accuracy of ±20%.
f
EL
(
Hz
)
=
360
R
EL
(
M
Ω
)
Figure 4. 300Hz Output Waveform
Enable Function
The MIC4830 is disabled by connecting the external
resistor (Rsw) to GND. This turns off the switch
oscillator of the boost converter. Connecting the
external resistor (Rsw) to V
DD
enables the oscillator
and turns on the device. The enable voltage should
rise or fall monotonically without interruption.
July 2009
7
M9999-070709-C
MICREL [ MICREL SEMICONDUCTOR ]
