MICREL MIC4832YMM

MIC4832
Low Noise 220Vp-p EL Driver
General Description
Features
The MIC4832 is a low noise 220Vp-p electroluminescent
lamp (EL) driver. Using advanced Bipolar, CMOS, DMOS
(BCD) technology, the MIC4832 integrates a high voltage
boost converter and an H-bridge driver for driving a large
EL lamp. The MIC4832 can drive large panel displays for
mobile phones, multimedia players or automotive
electronics where EL panels are used for backlighting.
The MIC4832 offers design flexibility with adjustable lamp
and boost converter frequencies, simply by applying
external resistors. A new H-Bridge design reduces audible
noise by creating smoother AC voltage across the EL
panel.
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The MIC4832 is offered in MLF® 3mm x 3mm and MSOP8 lead-free and RoHS compliant packaging with a -40°C to
85°C junction temperature range.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
1.8V to 5.5V DC input voltage
220Vpp output voltage capable
Low audible noise EL drive waveform
Supports EL panel sizes up to 3in2 (19cm2)
Low 45µA operating supply current
Small inductor size with low profile (220uH)
Tiny 8-pin 3mm x 3mm MLF® package
Adjustable boost converter frequency
Adjustable EL lamp frequency
10nA shutdown current
Applications
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LCD panel backlight
Mobile Phones
PDAs
Pagers
Calculators
Multimedia Players
Remote controls
GPS Receivers
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Typical Application
Low Noise EL Driver
MLF and MicroLeadFrame is a registered trademark of Amkor Technologies, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
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MIC4832
Ordering Information
Part Number
Junction Temp. Range
Package
Lead Finish
®
MIC4832YML
–40° to +85°C
8-Pin 3mm × 3mm MLF
RoHS Compliant / Pb-Free / Halogen Free*
MIC4832YMM
–40° to +85°C
8-Pin MSOP
RoHS Compliant / Pb-Free
Note
*MLF® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Pin Configuration
8-Pin 3mm × 3mm MLF® (ML)
8-Pin MSOP (MM)
Pin Description
Pin Number
Pin Name
1
VDD
2
RSW
Pin Function
Supply (Input): 1.8V to 5.5V for internal circuitry.
Switch Resistor (External Component): Set switch frequency of the internal
power MOSFET by connecting an external resistor to VDD. Connecting the
external resistor to GND disables the switch oscillator and shuts down the
device.
3
REL
EL Resistor (External Component): Set EL frequency of the internal H-bridge
driver by connecting an external resistor to VDD. Connecting the external
resistor to GND disables the EL oscillator.
4
GND
Ground
5
SW
Switch Node (Input): Internal high-voltage power MOSFET drain.
6
CS
Regulated Boost Output (External Component): Connect to the output
capacitor of the boost regulator and connect to the cathode of the diode.
7
VB
EL Output: Connect to one end of the EL lamp. Polarity is not important.
8
VA
EL Output: Connect to one end of the EL lamp. Polarity is not important.
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MIC4832
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VDD)...................................... –0.5V to 6.0V
Output Voltage (VCS) ..................................... –0.5V to 120V
EL Lamp Terminals (VA, VB)................................... VCS + 3V
Switch Voltage (Vsw) ..................................... -0.5V to 120V
Frequency Control Voltage
(VRSW, VREL) ................................... –0.5V to (VDD +0.3V)
Storage Temperature (TS).........................–65°C to +150°C
ESD Rating(4) ............................................................... 1.5kV
Supply Voltage (VDD).................................... +1.8V to +5.5V
Lamp Drive Frequency (fEL) ....................... 60Hz to 1000Hz
Switching Frequency (fSW).........................65kHz to 250kHz
Ambient Temperature (TA) .......................... –40°C to +85°C
Package Thermal Resistance(3)
MSOP (θJA) .....................................................206°C/W
MLF-8L (θJA)......................................................63°C/W
Electrical Characteristics(5)
VIN = VDD = 3.0V, RSW = 338KΩ, REL = 1.78MΩ. TA = 25°C unless otherwise specified. Bold values indicate –40°C ≤ TA ≤ +85°C
Parameter
Condition
On-resistance
ISW = 100mA
Min
91
CS Voltage Variation
Enable Input Low Voltage
(turn-off)
VDD = 1.8V to 5.5V
Enable Input High Voltage
(turn-on)
VDD = 1.8V to 5.5V
Shutdown current
RSW Resistor = LOW; REL Resistor = LOW; VDD = 5.5V
Input supply current
RSW Resistor = HIGH;
REL Resistor = HIGH;
Typ
Max
Units
3.8
7
Ohm
105
119
0.5
V
VDD0.5
V
0.01
0.5
µA
45
75
µA
VCS = 110V; VA, VB OPEN
Input current including
inductor
VIN = VDD = 3.2V; RSW = 338KΩ, REL = 1.78MΩ;
VA – VB output drive
frequency
REL = 1.78MΩ
Switching transistor
frequency
RSW = 338KΩ
24
L=220µH; ROUT =10kΩ; Lamp = 2in2
mA
158
200
242
Hz
90
112
134
kHz
Switching transistor duty
cycle
90
%
Notes:
1.
Exceeding the absolute maximum rating may damage the device.
2.
The device is not guaranteed to function outside its operating rating.
3.
The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = (TJ(max) – TA) / θJA. Exceeding the maximum
allowable power dissipation will result in excessive die temperature.
4.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
5.
Specification for packaged product only.
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MIC4832
Typical Characteristics
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Functional Diagram
Figure 1. MIC4832 Block Diagram
Functional Description
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 VOUT + VD1. The energy in the inductor is then
discharged into the COUT 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, VA and VB 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.
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 in2. 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
VDD. The internal feedback voltage is less than the
reference voltage causing the internal comparator to
go low 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
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MIC4832
L = 220µH
COUT = 2.7nF
LAMP = 2 in2
RSW = 300k
LAMP = 2 in2
RSW = 332k
REL = 2.82M
REL = 1.78M
VA - VB
(100V/div)
VA - VB
(100V/div)
VB
(50V/div)
COUT = 2.7nF
VA
(50V/div)
L = 220µH
VIN = 3.6V
IIN = 27mA
VB
(50V/div)
VA
(50V/div)
VIN = 3.6V
IIN = 17mA
Time (2ms/div)
Time (2ms/div)
Figure 2. 100Hz Output Waveform
f SW (kHz) =
36
R SW (MΩ )
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 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%.
fEL (Hz ) =
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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)
VIN = 3.6V
IIN = 21mA
L = 220µH
COUT = 2.7nF
LAMP = 1 in2
RSW = 353k
VB
(50V/div)
REL = 1.1M
VA - VB
(100V/div)
Switching Frequency
The switching frequency of the converter is
controlled via an external resistor between RSW pin
and VDD 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.
Figure 3. 200Hz Output Waveform
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 VDD enables the oscillator
and turns on the device. The enable voltage should
rise or fall monotonically without interruption.
360
R EL (MΩ )
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Application Information
Inductor
A 220µH Murata (LQH4C221K04) inductor is
recommended for most applications. Generally,
inductors with smaller values can handle more
current. Lowering the inductance allows the boost
regulator to draw more input current to deliver more
energy every cycle. As a result, a lower value
inductor may be used to drive larger panels or make
the current panel brighter. However, caution is
required as using a low value inductor with a low
switching frequency may result in voltages
exceeding the absolute maximum rating of the
switch node and/or the CS pin. If the application
uses a low input voltage (1.8 to 3V), a lower value
inductor, such as 100µH, may be used in order to
drive the EL lamp at max brightness without issue.
Diode
An ideal diode to use would be the 1N4148 or
equivalent. It has a forward current of 150mA and a
typical forward voltage of 950mV. For applications
that are not cost driven, a fast switching diode with
lower forward voltage and higher reverse voltage
can be used to enhance the efficiency, such as
BAV20WS or BAS20W.
Output Capacitor
Low ESR capacitors should be used at the regulated
boost output (CS pin) of the MIC4832 to minimize
the switching output ripple voltage. The larger the
output capacitance, the lower the output ripple at the
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CS pin. The reduced output ripple at the CS pin
along with a low ESR capacitor improves the
efficiency of the MIC4832 circuit. Selection of the
capacitor value will depend upon the peak inductor
current, inductor size, and the load. The MIC4832 is
designed for use with an output capacitance as low
as 2.2nF. For minimum audible noise, the use of a
C0G/NPO
dielectric
output
capacitor
is
recommended. TDK and AVX offer C0G/NPO
dielectric capacitors in capacitances up to 2.7nF at
200V to 250V rating in 0805 size. If output ripple is a
concern a 0.01µF/200V X7R output capacitor is
recommended.
EL Lamp Terminals (VA, VB)
An EL lamp is connected from VA to VB as the load.
The high voltage alternated across VA and VB by
the H-Bridge cycles generate luminance. The
voltage at VA and VB should not exceed the voltage
at VCS by more than 3V. This situation may become
present when noisy enable signals such as those
often generated by mechanical switches are applied
to the driver’s inputs. To prevent over voltage at VA
and VB, 10kΩ resistors may be placed in series from
VA to the EL panel and from VB to the EL panel. An
alternative to the use of 10kΩ resistors is to apply a
diode from the CS pin to VA and VB, where the
cathode of the diode is on the CS side and the
anode is on the VA and VB side, respectively.
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Application Circuit
Figure 5: Typical Li-Ion Powered MIC4832 Circuit
Size
(inch2)
Capacitance
(nF)
0.4
2
1
5
2
10
3
15
Lamp Frequency
(Hz)
100
200
300
400
500
600
700
800
900
REL (MΩ)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
2.82
240
150
257
140
300
120
313
115
1.69
252
143
295
122
333
108
1.1
273
132
353
102
0.837
281
128
0.665
257
116
0.562
269
105
0.471
281
98
0.409
0.369
Note: Table 1 applies to circuit shown in Figure 5.
Table 1: Recommended RSW & REL values for various panel sizes
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MIC4832
Layout Recommendation
Top
Bottom
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MIC4832
Package Information
8-Pin MSOP (MM)
8-Pin 3mm x 3mm MLF (ML)
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MIC4832
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2007 Micrel, Incorporated.
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