MICREL MIC4834YMM

MIC4834
Low Noise Dual 220 VPP EL Driver
General Description
Features
The MIC4834 is a low noise dual Electroluminescent (EL)
Panel driver used in backlighting applications. The
MIC4834 converts a low DC voltage to a high DC voltage
using a boost converter and then alternates the high DC
voltage across the EL panels using an H-bridge. The
MIC4834 incorporates internal wave-shaping circuitry
specifically designed to reduce audible noise emitted by
EL panels. With only one inductor the MIC4834 can drive
two outputs and requires a minimum number of passive
components. It features an operating input voltage range
of 2.3V to 5.8V, making it suitable for 1-cell Li-ion and 2- or
3-cell alkaline/NiCad/NiMH battery applications.
The MIC4834 features separate oscillators for the boost
and H-bridge stages. The boost frequency may be
adjusted with an external resistor to optimize efficiency
and brightness. The H-bridge frequency is internally preset
to 225Hz, to reduce the number of external components
and layout space.
The MIC4834 is available in 10 pin 3mmx3mm MLF®
package as well as MSOP-10L, and has an operating
junction temperature range of –40°C to +125°C.
•
•
•
•
•
•
•
•
•
Drives two EL panels, up to 3 in2 each at full
brightness
220VPP regulated AC output waveform
2.3V to 5.8V DC input voltage
Wave-shaping circuit to reduce audible noise
Adjustable boost converter frequency
Single inductor to power both panels
0.1µA typical shutdown current
Package options
− 10-pin 3mmx3mm MLF®
− 10-pin MSOP
–40oC to +125oC junction temperature range
Applications
•
•
•
•
•
•
•
Mobile phones
MP3/portable media players (PMP)
Clocks/ watches
Remote controls
Cordless phones
GPS devices
PDAs
_________________________________________________________________________________________________
Typical Application
Low Noise Dual EL Driver
MLF and MicroLead Frame are registered trademark of Amkor Technologies
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
October 2008
M9999-100808-A
Micrel
MIC4834
Ordering Information
Part Number
Package
Operating Junction Temp Range
Lead Finish
MIC4834YML
10 pin (3mm x 3mm) MLF®
-40ºC to +125ºC
Pb-free / RoHS-Compliant
MIC4834YMM
10-Pin MSOP
-40ºC to +125ºC
Pb-free / RoHS-Compliant
Pin Configuration
®
10-Pin MLF - Top View
10-Pin MSOP – Top View
Pin Description
Pin Number
Pin Name
Pin Function
1
ENA
EL Panel A Enable Pin: Logic high enables ELA and logic low disables ELA output.
2
VDD
DC Input Supply Voltage: 2.3V to 5.8V
3
RSW
RSW pin: Sets internal boost converter switch frequency by connecting an external
resistor (RSW) to VDD. Connecting the RSW resistor to GND shuts down the device.
4
ENB
EL Panel B enable pin: Logic high enables ELB and logic low disables ELB output.
5
GND
Ground.
6
SW
Switch Node: Drain of internal high-voltage power MOSFET for boost circuit.
7
CS
Regulated Boost Output: Connect to the output capacitor of the boost regulator and
to the cathode of the diode.
8
COM
EL output: Common EL output terminal to both ELA and ELB. Connect one end of
each EL panel to this pin.
9
ELB
EL Panel B output: Connect the other end of the EL panel B to this pin.
10
ELA
EL Panel A output: Connect the other end of the EL panel A to this pin.
EPad
HS Pad
October 2008
Heat Sink Pad. Connect to ground externally. MLF® package only.
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MIC4834
Absolute Maximum Rating(1)
Operating Range(2)
Supply voltage (VDD) ....................................... -0.5V to 6.5V
Output voltage (VCS)...................................... -0.5V to 130V
Switch Node (VSW) ......................................... -0.5V to 130V
Enable Voltage (VRSW, VENA, VENB)................... -0.5V to 6.5V
Ambient Storage Temperature (TS) ........... -65ºC to +150ºC
ESD Rating(3) ........................................................................... ESD Sensitive
Supply Voltage (VDD) ........................................2.3V to 5.8V
Switching MOSFET Frequency (fSW) ........ 35kHz to 350kHz
Enable Voltage (VRSW, VENA,, VENB) ....................... 0V to VDD
Junction Temperature Range (TJ) ............. -40°C to +125°C
Package Thermal Impedance
3mm x 3mm MLF® (θJA)……………………........ 60°C/W
MSOP (θJA)……………………......................... 206°C/W
Electrical Characteristics(4)
TA = 25oC, VDD= 3.0V unless otherwise noted. Bold values indicate -40°C ≤ TJ ≤ 85°C.
Symbol
Parameter
VDD
Supply Voltage Range
IDD
Input Supply Current
VRSW = High; VCS = 105V;
ELA, ELB, COM = Open
ISD
Shutdown Current
RDS(ON)
VCS
fSw
Max
Units
5.8
V
152
220
µA
VRSW = Low; VDD = 5.8V
0.1
1
µA
On-resistance Of Switching Transistor
ISW = 100mA, VCS = 105V
6.0
12.0
Ω
Output voltage Regulation
VDD = 2.3V to 5.8v
90
109
120
V
VDD = 3.0V
(RSW = 1.3MΩ )
25
35
45
kHz
VDD = 3.0V
(RSW = 450kΩ)
75
100
125
kHz
VDD = 3.0V
(RSW = 125kΩ)
250
350
450
kHz
VDD = 3.0V
ELA, ELB, COM = Open
165
225
285
Hz
95
%
7.5
mA
1.2
V
50
150
mV
0.1
1
µA
Boost Switching Frequency
Condition
Min
Typ
2.3
fEL
ELA, ELB and COM Drive Frequency
D
Switching Transistor Duty Cycle
80
IOUT
Output Current Drive Limit
2.5
VENA,
VENB
Enable Logic Threshold
0.4
VHYS
Enable Logic Hysteresis
20
IENA,
IENB
Enable Input Current
5
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
4. Specification for packaged product only.
October 2008
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MIC4834
Recommended Switching
Frequency Vs. Total Lamp Size
300
250
200
150
100
50
C
= 2.2nF
30
f
= 94kHz
25
Size = 2in2
100
80
60
40
20
EL
= 225Hz
OUT
SW
20
15
10
5
f
SW
= 116kHz
2
OUT
50
1400
fSW = 62kHz
45
2
Size = 4in
40
35
f
SW
90
85
= 225Hz
= 2.2nF
= 82kHz
2
3
4
5
6
OUT
f
= 2.2nF
= 42kHz
SW
2
Size = 6in
65
60
55
50 f = 50kHz
SW
45
Size = 5in2
40
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
16
240
120
fEL = 225Hz
C
80
75
70
Output Voltage
vs. Input Voltage
100
80
60
40
f
SW
= 45kHz
20 fEL = 225Hz
COUT = 2.2nF
0
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
Brightness
vs. Input Voltage
14
160
120
SW
= 45kHz
40 fEL = 225Hz
C
= 2.2nF
OUT
0
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
October 2008
BRIGHTNESS (lux)
200
80 f
1
CS VOLTAGE (V)
EL
C
1200
800
f
55
1000
600
CS Voltage
vs. Input Voltage
400
Total Input Current
vs. Input Voltage
200
Total Input Current
vs. Input Voltage
0
0
2
Size = 3in2
20
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (VP-P)
f
TOTAL LAMP SIZE (in )
INPUT CURRENT (mA)
INPUT CURRENT (mA)
35
SWITCHING RESISTOR (kOhm)
60
25
40
120
Size = 1in
0
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
0
30
Total Input Current
vs. Input Voltage
140
INPUT CURRENT (mA)
350
SWITCHING FREQUENCY (kHz)
Switching Frequency
vs SW Resistor
400
0
SWITCHING FREQUENCY (kHz)
Typical Characteristics
12
10
8
6
Distance = 2 in
fSW = 135kHz
4
f
2
EL
= 225Hz
L = 220µH
0
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
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MIC4834
Functional Diagram
Figure 1. MIC4834 Block Diagram
Functional Description
programmed through an external resistor to maximize
efficiency and brightness of the EL panel. The H-bridge
frequency is internally fixed at 225Hz to reduce external
component count.
Overview
The MIC4834 is a high-voltage dual output EL driver with
a peak-to-peak AC output voltage of 220V capable of
driving two 3 in2 EL panels. The MIC4834 drives EL
panels by converting a low DC input voltage to a high
DC high output voltage using the boost regulator circuit
and then alternating the high DC voltage across the EL
panel using an H-Bridge. Input supply current for the
MIC4834 is typically 152µA. The high voltage EL driver
has two internal oscillators to control the boost switching
frequency and the H-bridge driver frequency. The
internal boost oscillator frequency can be individually
October 2008
Regulation
Referring to Figure 1, power is initially applied to VDD.
When the internal feedback voltage is less than the
reference voltage, the internal comparator enables
switching in the boost circuit. When the boost regulator
is switching, current flows through the inductor into the
switch. The switching MOSFET will typically turn on for
90% of the switching period. During the on-time, energy
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MIC4834
ENA or ENB high (over 1.2V) or low (below 0.4V) will
turn ELA and ELB panels on or off.
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 disables switching. The control
circuit will continue to turn the MOSFET’s on and off to
maintain a constant DC voltage at the CS pin.
When the MIC4834 EL Driver is enabled, ELA and ELB
will switch in opposite states with COM to achieve a
220V peak-to-peak AC output signal needed to drive the
two EL panels.
Figure 2. EL Panel Waveform – 2 × 1 in2
Switching Frequency
The switching frequency of the converter is controlled by
an external resistor (RSW) between RSW and VDD. The
switching frequency increases as the resistor value
decreases. In general, the lower the switching
frequency, the greater the input current is drawn to
deliver more power to the output. Lowering the switching
frequency can be used to drive larger panels. However,
the switching frequency should not be so low as to allow
the voltage at the switch node or the CS pin to exceed
the absolute maximum voltage of those pins. For resistor
value selections, see the “Typical Characteristics:
Switching Frequency vs. SW Resistor” graph on Page 4
or use the equation below. The switching frequency
range is 35kHz to 350kHz, with an accuracy of ±20%.
fSW (kHz) =
2
Figure 3. EL Panel Waveform – 2 × 2 in
46
R SW (MΩ )
EL Frequency
The MIC4834 EL panel frequency is internally fixed at
225Hz.
Enable Function
There are a few different ways to enable and disable the
MIC4834. The boost regulator may be disabled by
pulling the RSW resistor to ground. This turns off both the
EL panels by cutting power to the device completely.
The RSW resistor must be pulled to VDD to enable the
boost oscillator. If it is not equal to VDD, then the
frequency set by RSW will be different the programmed
value.
For individual panel control, the ENA and ENB pins can
be used to enable ELA and ELB, respectively. Pulling
October 2008
Figure 4. EL Panel Waveform – 2 × 3 in2
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MIC4834
Output Capacitor
Low ESR capacitors should be used at the regulated
boost output (CS pin), 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 MIC4834 circuit.
Selection of the capacitor value depends upon the peak
inductor current, inductor size, and the load. The
MIC4834 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
capacitance up to 2.7nF at 200V to 250V voltage rating
in 0805 size.
Application Information
The MIC4834 is designed to use an inductance with a
value between 100µH to 330µH. Choosing the right
inductor is always a balance of size, inductance,
efficiency, current rating and cost. A TDK (VLS4012T221M) 220µH inductor is recommended based on size,
efficiency and current rating.
Generally, the lower the inductance, the more current
the inductor can handle. Lowering the inductance allows
the boost regulator to draw more input current to deliver
more energy every switching cycle. As a result, a lower
inductance may be used to drive larger panels or
brighten similar sized panels. However, caution is
required as using a low inductance with a low switching
frequency may cause the voltage at the switch node and
the CS pin to exceed the absolute maximum rating. If
the application uses a low input voltage (2.3V to 3V),
then a lower value inductor, such as 100µH, may be
used in order to drive the EL panel at maximum
brightness.
EL Panel Terminals (ELA, ELB, COM)
The two EL panels are connected from ELA to COM and
ELB to COM. The ELA and ELB terminals are in phase
with each other, while the COM is out of phase with both
ELA and ELB. Since ELA and COM are out of phase,
the high voltage generated by the boost regulator is
alternated across ELA and COM by the H-Bridge. The
frequency of each cycle is internally fixed at 225Hz. The
alternating 220V peak-to-peak causes the EL panel to
emit light. Similarly, the ELB and COM are also out of
phase and allows a second EL panel to be driven at the
same time. Both EL panels may operate independently
from each other and do not have to be the same size.
For component selection, Table 2 lists recommended
values for various panel sizes up to a total of 6 in2 (For
example, two 3 in2 panels). Driving overly large panels
will result in a dimmer display, but will not cause damage
to the device.
Diode
The diode must have a high reverse voltage (150V),
since the output voltage at the CS pin can reach up to
130V. A fast switching diode with lower forward voltage
and higher reverse voltage (150V), such as
BAV20WS/BAS20W, can be used to enhance efficiency.
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MIC4834
Application Circuit
Figure 6. Typical Li-Ion Powered MIC4834 Circuit
Note: Table 2 applies to circuit shown in Figure 6.
Total Panel Area (in2)
0.4
1
2
3
4
5
6
Capacitance (nF)
2
5
10
15
20
25
30
RSW (kΩ)
357
392
487
562
750
931
1100
fSW (kHz)
128
116
94
82
62
50
42
Table 2. Recommended RSW Values for Total Panel Sizes
Bill of Materials
Item
Part Number
C1
C1608X7R1A103K
TDK(1)
C1608X5R0J106K
C2
C3
C2012C0G2E2222J
L1
VLS4012T-221M
D1
BAS20-V-GS18
R1 or RSW
U1
CRCW06033323FKEYE3
MIC4834YML
Manufacturer
Description
Qty
0.01µF Ceramic Capacitor, 10V, X7R, Size 0603
1
TDK
(1)
10 µF Ceramic Capacitor, 6.3V, X5R, Size 0603
1
TDK
(1)
0.0022µF Ceramic Capacitor, 250V, C0G, Size 0805
1
TDK
(1)
220µH, 210mA ISAT. (4mmx4mmx1.2mm)
1
200V/200mA Hi-Voltage Switching Diode
1
(2)
332kΩ, 1%, 1/16W, Size 0603
1
(3)
Low Noise Dual 220Vp-p EL Driver with Output Slew Control
1
Vishay(2)
Vishay
Micrel
Notes:
1.
TDK: www.tdk.com
2.
Vishay: www.vishay.com
3.
Micrel, Inc.: www.micrel.com
October 2008
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M9999-100908-A
Micrel
MIC4834
Layout Recommendation (MLF®)
Top Layer
Bottom Layer
October 2008
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M9999-100908-A
Micrel
MIC4834
Layout Recommendation (MSOP)
Top Layer
Bottom Layer
October 2008
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MIC4834
Package Information
10-Pin 3mm x 3mm MLF® (ML)
October 2008
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MIC4834
10-Pin MSOP (MM)
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.
© 2008 Micrel, Incorporated.
October 2008
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