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MIC4832YMM

P1-P3P4-P6P7-P9P10-P11
Micrel MIC4832
March 2009
4
M9999-033109-C
Typical Characteristics
Micrel MIC4832
March 2009
5
M9999-033109-C
Functional Diagram
Figure 1. MIC4832 Block Diagram
Functional Description
Overview
The MIC4832 is a high-voltage EL driver with an AC
output voltage of 220V peak-to-peak capable of
driving EL lamps up to 3 in
2
. Input supply current for
the MIC4832 is typically 45µA reducing to 10nA in
shutdown. The high voltage EL driver has two
internal oscillators to control the switching MOSFET
and the H-bridge driver. Both of the internal
oscillators’ frequencies can be individually
programmed through the external resistors to
maximize the efficiency and the brightness of the EL
lamp.
Regulation
Referring to Figure 1, initially power is applied to
V
DD
. The internal feedback voltage is less than the
reference voltage causing the internal comparator to
go high which enables the switching MOSFET’s
oscillator. When the switching MOSFET turns on,
current flows through the inductor and flows into the
switch. The switching MOSFET will typically turn on
for 90% of the switching period. During the on-time,
energy is stored in the inductor. When the switching
MOSFET turns off, current flowing into the inductor
forces the voltage across the inductor to reverse
polarity. The voltage across the inductor rises until
the external diode conducts and clamps the voltage
at V
OUT
+ V
D1
. The energy in the inductor is then
discharged into the C
OUT
capacitor. The internal
comparator continues to turn the switching MOSFET
on and off until the internal feedback voltage is
above the reference voltage. Once the internal
feedback voltage is above the reference voltage, the
internal comparator turns off the switching
MOSFET’s oscillator.
When the EL oscillator is enabled, V
A
and V
B
switch
in opposite states to achieve a 220V peak-to-peak
AC output signal. The external resistor that connects
to the REL pin determines the EL frequency.
Micrel MIC4832
March 2009
6
M9999-033109-C
V
IN
= 3.6V
I
IN
= 17mA
L = 220µH
C
OUT
= 2.7nF
LAMP = 2 in
2
R
SW
= 300k
R
EL
= 2.82M
VA - VB
(100V/div)
VB
(50V/div)
VA
(50V/div)
Time (2ms/div)
Figure 2. 100Hz Output Waveform
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.
()
Ω
=
MR
36
(kHz)f
SW
SW
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%.
()
()
Ω
=
MR
360
Hzf
EL
EL
V
IN
= 3.6V
I
IN
= 27mA
L = 220µH
C
OUT
= 2.7nF
LAMP = 2 in
2
R
SW
= 332k
R
EL
= 1.78M
VA - VB
(100V/div)
VB
(50V/div)
VA
(50V/div)
Time (2ms/div)
Figure 3. 200Hz Output Waveform
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.
V
IN
= 3.6V
I
IN
= 21mA
L = 220µH
C
OUT
= 2.7nF
LAMP = 1 in
2
R
SW
= 353k
R
EL
= 1.1M
VA - VB
(100V/div)
VB
(50V/div)
VA
(50V/div)
Time (2ms/div)
Figure 4. 300Hz Output Waveform
Enable Function
The MIC4832 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.
P1-P3P4-P6P7-P9P10-P11

MIC4832YMM

Mfr. #:
Buy MIC4832YMM
Manufacturer:
Microchip Technology / Micrel
Description:
LED Lighting Drivers 220Vpp Low Noise EL Driver
Lifecycle:
New from this manufacturer.
Delivery:
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