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MIC4832
Datasheet (Micrel)
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Datasheet MIC4832 Datasheet (Micrel)

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Page 1
General Description
MIC4832
Low Noise 220Vp-p EL Driver
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.
The MIC4832 is offered in MLF 8 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.
___________________________________________________________________________________________________________
®
3mm x 3mm and MSOP-
• 1.8V to 5.5V DC input voltage
• 220Vpp output voltage capable
• Low audible noise EL drive waveform
• Supports EL panel sizes up to 3in
• Low 45µA operating supply current
• Small inductor size with low profile (220uH)
• Tiny 8-pin 3mm x 3mm MLF
• Adjustable boost converter frequency
• Adjustable EL lamp frequency
• 10nA shutdown current
2
(19cm2)
®
package
Applications
• LCD panel backlight
• Mobile Phones
• PDAs
• Pagers
• Calculators
• Multimedia Players
• Remote controls
• GPS Receivers
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 (
November 2007
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
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Micrel 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
Pin Description
Pin Number Pin Name Pin Function
1 VDD Supply (Input): 1.8V to 5.5V for internal circuitry.
2 RSW Switch Resistor (External Component): Set switch frequency of the internal
3 REL EL Resistor (External Component): Set EL frequency of the internal H-bridge
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
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.
8-Pin MSOP (MM)
8-Pin 3mm × 3mm MLF
power MOSFET by connecting an external resistor to VDD. Connecting the
external resistor to GND disables the switch oscillator and shuts down the device.
driver by connecting an external resistor to VDD. Connecting the external resistor to GND disables the EL oscillator.
capacitor of the boost regulator and connect to the cathode of the diode.
®
(ML)
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Micrel MIC4832
Absolute Maximum Ratings
(1)
Operating Ratings
(2)
Supply Voltage (VDD)...................................... –0.5V to 6.0V
Output Voltage (V EL Lamp Terminals (V
) ..................................... –0.5V to 120V
CS
, VB)................................... VCS + 3V
A
Switch Voltage (Vsw) ..................................... -0.5V to 120V
Frequency Control Voltage (V Storage Temperature (T ESD Rating
RSW
,
V
) ................................... –0.5V to (V
REL
).........................–65°C to +150°C
(4)
............................................................... 1.5kV
S
DD
+0.3V)
Supply Voltage (VDD).................................... +1.8V to +5.5V
Lamp Drive Frequency (f Switching Frequency (f Ambient Temperature (T Package Thermal Resistance
) ....................... 60Hz to 1000Hz
EL
).........................65kHz to 250kHz
SW
) ..........................–40°C to +85°C
A
(3)
MSOP (θJA) .....................................................206°C/W
JA
MLF-8L (θ
)...................................................... 63°C/W
Electrical Characteristics
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 Min Typ Max Units
On-resistance ISW = 100mA 3.8 7 Ohm
CS Voltage Variation
Enable Input Low Voltage (turn-off)
Enable Input High Voltage (turn-on)
Shutdown current RSW Resistor = LOW; REL Resistor = LOW; VDD = 5.5V 0.01
Input supply current
Input current including inductor
VA – VB output drive frequency
Switching transistor frequency
Switching transistor duty cycle
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 T 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.
(5)
91
V
= 1.8V to 5.5V 0.5 V
DD
V
= 1.8V to 5.5V
DD
VDD-
105
V
119
0.5
0.5
R
Resistor = HIGH;
SW
R
Resistor = HIGH;
EL
45
75
VCS = 110V; VA, VB OPEN
V
= VDD = 3.2V; RSW = 338KΩ, REL = 1.78MΩ;
IN
L=220µH; R
R
= 1.78MΩ
EL
R
= 338KΩ
SW
=10kΩ; Lamp = 2in2
OUT
(ambient temperature) is PD(max) = (TJ(max) – TA) / θJA. Exceeding the maximum
A
24 mA
158 200 242 Hz
90 112 134 kHz
90 %
µA
µA
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Micrel MIC4832
Typical Characteristics
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Micrel MIC4832
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
. The internal feedback voltage is less than the
DD
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
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 discharged into the C
+ VD1. The energy in the inductor is then
OUT
capacitor. The internal
OUT
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
and VB switch
A
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.
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Micrel MIC4832
VIN = 3.6V
I
= 17mA
VA
(50V/div)
VB
(50V/div)
VA - V B
(100V/div)
Time (2ms/div)
IN
L = 220µH
C
= 2.7nF
OUT
LAMP = 2 in RSW = 300k
= 2.82M
R
EL
2
Figure 2. 100Hz Output Waveform
Switching Frequency
The switching frequency of the converter is controlled via an external resistor between R and V
pin of the device. The switching frequency
DD
SW
pin
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.
SW
(kHz)f
36
SW
()
Ω=MR
EL Frequency
The EL lamp frequency is controlled via an external resistor connected between R
pin and VDD pin of
EL
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%.
VIN = 3.6V
I
= 27mA
VA
(50V/div)
VB
(50V/div)
VA - V B
(100V/div)
Time (2ms/div)
IN
L = 220µH
C
= 2.7nF
OUT
LAMP = 2 in RSW = 332k
= 1.78M
R
EL
2
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.
VIN = 3.6V
I
= 21mA
VA
(50V/div)
VB
(50V/div)
VA - V B
(100V/div)
Time (2ms/div)
IN
L = 220µH
C
= 2.7nF
OUT
LAMP = 1 in RSW = 353k
= 1.1M
R
EL
2
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
enables the oscillator
DD
and turns on the device. The enable voltage should rise or fall monotonically without interruption.
()
Hzf
EL
360
EL
()
Ω=MR
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Micrel MIC4832
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
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 V
by more than 3V. This situation may become
CS
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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Micrel MIC4832
Application Circuit
Figure 5: Typical Li-Ion Powered MIC4832 Circuit
Size
(inch
2
)
Capacitance
(nF)
Lamp Frequency
R
0.4 2
1 5
2 10
3 15
Note: Table 1 applies to circuit shown in Figure 5.
Table 1: Recommended RSW & REL values for various panel sizes
RSW (kΩ)
SW
f RSW (kΩ)
SW
f RSW (kΩ)
SW
f RSW (kΩ)
SW
f
(Hz)
EL
(MΩ)
(kHz)
(kHz)
(kHz)
(kHz)
100 200 300 400 500 600 700 800 900
2.82 1.69 1.1 0.837 0.665 0.562 0.471 0.409 0.369 240 252 273 281 257 269 281 150 143 132 128 116 105 98 257 295 353 140 122 102 300 333 120 108 313 115
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Micrel MIC4832
Layout Recommendation
Top
Bottom
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Micrel MIC4832
Package Information
8-Pin MSOP (MM)
8-Pin 3mm x 3mm MLF (ML)
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Micrel 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
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
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
indemnify Micrel for any damages resulting from such use or sale.
© 2007 Micrel, Incorporated.
November 2007 11
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