MICREL MIC4833

MIC4833
Low Noise Dual 220 VPP EL Driver
With Output Voltage Slew Rate Control
General Description
Features
The MIC4833 is a low noise dual Electroluminescent (EL)
Panel driver used in backlighting applications. The
MIC4833 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
MIC4833 incorporates internal wave-shaping circuitry
specifically designed to reduce audible noise emitted by
EL panels. The two EL panels may be dimmed by applying
a PWM signal to the device. The MIC4833 drives two
outputs from a single inductor 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.
An external resistor may be used to adjust the output
voltage slew rate to reduce audible noise. The MIC4833
features separate oscillators for the boost and H-bridge
stages to allow independent control. External resistors set
the operating frequencies of each stage allowing the EL
circuit to optimize efficiency and brightness.
®
The MIC4833 is available in a 12 pin 3mmx3mm MLF
package, and has an operating junction temperature range
of –40°C to +125°C.
•
•
•
•
•
•
•
•
•
•
•
Drives two EL panels, up to 4 in2 each at full
brightness
Independent input control for each of the two panels
and allows PWM dimming.
220Vpp regulated AC output waveform
2.3V to 5.8V DC input voltage
Wave-shaping circuit to reduce audible noise
Adjustable slew rate for audible noise reduction
Independently adjustable boost converter and EL
panel frequency
Single inductor to power both panels
0.1uA typical shutdown current
®
12 pin 3mmx3mm MLF package
o
o
–40 C to +125 C junction temperature range
Applications
• Mobile Phones
• MP3s/Portable Media Players (PMP)
• Clocks/ Watches
• Remote Controls
• Cordless Phones
• GPS Devices
• PDAs
_________________________________________________________________________________________________
Typical Application
High
Low
VIN
Li Ion
3V to 4.2V
332k
0.01µF
1.78M
High
Low
50k
ENA
SLEW
VDD
ELA
EL Lamp A
ELB
EL Lamp B
RSW
MIC4833
REL
COM
ENB
CS
GND
SW
High
Low
VIN
Li Ion
3V to 4.2V
220µH
10µF
2.2nF
250V
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
M9999-100308
(408) 955-1690
Micrel
MIC4833
Ordering Information
Part Number
MIC4833YML
Package
Operating Junction Temp
Range
Lead Finish
-40°C to +125°C
Pb-free / RoHS Compliant
12 pin 3mmx3mm
®
MLF
Pin Configuration
ENA
1
12 SLEW
VDD
2
11
ELA
RSW
3
10
ELB
REL
4
9
COM
ENB
5
8
CS
GND
6
7
SW
EP
®
12-Pin 3mm × 3mm MLF (ML) – Top View
Pin Description
October 2008
Pin Number
Pin Name
1
ENA
2
3
VDD
RSW
4
REL
5
ENB
6
7
GND
SW
8
CS
9
COM
10
ELB
11
ELA
12
SLEW
EPad
HS Pad
Pin Function
EL Panel A Enable Pin: Logic high enables ELA and logic low disables
ELA output.
DC Input Supply Voltage: 2.3V to 5.8V
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.
REL pin: Sets internal H-bridge driver frequency by connecting an
external resistor (REL) to VDD. Connecting the REL to GND disables
the EL oscillator.
EL Panel B enable pin: Logic high enables ELB and logic low disables
ELB output.
Ground.
Switch Node: Drain of internal high-voltage power MOSFET for boost
circuit.
Regulated Boost Output: Connect to the output capacitor of the boost
regulator and to the cathode of the diode.
EL output: Common EL output terminal to both ELA and ELB. Connect
one end of each EL panel to this pin.
EL Panel B output: Connect the other end of the EL panel B to this
pin.
EL Panel A output: Connect the other end of the EL panel A to this
pin.
Optional resistor to set output current drive to control slew rate of load.
If left open, the default slew current limit is 5mA.
Heat Sink Pad. Connect to ground externally.
2
M9999-100308
(408) 955-1690
Micrel
MIC4833
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 (VENA, VENB) ..…...……………-0.5V to 6.5V
Voltage (VREL, VRSW, VSLEW) ......………...….…-0.5V to 6.5V
Ambient Storage Temperature (TS) …. ..... -65°C to +150°C
ESD Rating(3)…..……………………..………ESD Sensitive
Supply Voltage (VDD) ..………………………...2.3V to 5.8V
Panel Drive Frequency (fEL)……………..100Hz to 1500Hz
Switching MOSFET Frequency (fSW)…...35kHz to 350kHz
Enable Voltage (VENA, VENB) ……………………...0V to VDD
Junction Temperature Range (TJ) ………-40°C to +125°C
Package Thermal Impedance
θJA MLF®-12L …………………….................... 60°C/W
Electrical Characteristics(4)
TA=25oC, Vdd = 3.0V unless otherwise noted. Bold values indicate -40°C ≤ TJ ≤ 85°C.
Parameter
Symbol Condition
Supply Voltage Range
Input Supply Current
VDD
Shutdown Current
On-resistance Of Switching
Transistor
Output voltage Regulation
ISD
Boost Switching Frequency
IDD
RDS(ON)
VCS
fSw
ELA, ELB and COM Drive
Frequency
fEL
Switching Transistor Duty
Cycle
D
Output Current Drive Limit
Programmability
ISLEW
Enable Logic Threshold
Enable Logic Hysteresis
Enable Input Current
Min
Typ
Max
Units
5.8
V
152
220
µA
0.1
1
µA
6.0
12.0
Ω
90
109
120
V
25
35
45
kHz
75
100
125
kHz
250
350
450
kHz
175
235
295
Hz
445
565
685
Hz
95
%
2.3
RSW=High; VCS=105V;
ELA, ELB, COM, SLEW = Open
RSW=Low; VDD=5.8v
ISW=100mA, VCS=105V
VDD=2.3V to 5.8v
VDD=3.0V
(RSW = 1.3MΩ )
VDD=3.0V
(RSW = 450kΩ)
VDD=3.0V
(RSW = 125kΩ)
VDD=3.0V
(REL = 1.8 MΩ) ELA, ELB = Open
Vdd=3.0V
(REL = 712kΩ) ELA, ELB = Open
80
SLEW = Open
2.5
5
7.5
mA
RSLEW =10kΩ
7
10
13
mA
50
0.1
1.2
150
1
V
mV
µA
0.4
20
VENA, VENB
VHYS
IENA, IENB
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
3
M9999-100308
(408) 955-1690
Micrel
MIC4833
1
2
3
4
ELRESISTOR (MOhm)
Input Current vs.
EL Frequency (Dual EL Lamp)
2× 2 in
2× 1 in
2
VIN = 3.6V
f
= 75kHz
140
120
100
80
300Hz
60 400Hz
40
20
VIN = 3.0V
f
EL
35
= 200Hz
C
= 2.2nF
f
= 100kHz
OUT
30
25
SW
Size = 2in
20
2
15
10
5
f
SW
= 122kHz
2
500
350
450
CS Voltage
vs. Input Voltage
SW
400
Total Input Current
vs. Input Voltage
300
Total Input Current
vs. Input Voltage
250
TOTAL LAMP SIZE (in )
200
EL FREQUENCY (Hz)
Size = 1in
0
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
80
75
OUT
f
SW
= 2.2nF
= 68kHz
2
Size = 4in
35
30
25
20 f = 88kHz
SW
15
Size = 3in2
10
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
INPUT CURRENT (mA)
C
0
0
1
2
3
4
5
6
2
fEL = 200Hz
50
45
40
240
f
EL
OUT
f
= 2.2nF
= 47kHz
SW
2
Size = 6in
55
50
45
40 f = 55kHz
SW
35
Size = 5in2
30
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
16
120
= 200Hz
C
70
65
60
Output Voltage
vs. Input Voltage
100
80
60
40
f
SW
= 45kHz
20 fEL = 200Hz
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 = 200Hz
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
150Hz
200Hz
Total Input Current
vs. Input Voltage
40
CS VOLTAGE (V)
60
55
INPUT CURRENT (mA)
2
2
150
25
20
15
10
2× 3 in
160
INPUT CURRENT (mA)
50
45
40
35
30
EL FREQUENCY (Hz)
Recommended Switching
Frequency vs. Total Lamp Size
SWITCHING FREQUENCY (kHz)
2× 4 in2
100
INPUT CURRENT (mA)
60
55
10
0
5
2
500
0
0
1400
1200
800
1000
200
600
0
400
200
1 in
20
450
400
2
2
2 in2
30
400
50
600
3 in
40
350
100
800
4 in
300
150
1000
250
200
1200
VIN = 3.6V
50 fSW = 75kHz
200
250
INPUT CURRENT (mA)
EL FREQUENCY (Hz)
300
SWITCHING RESISTOR (kOhm)
OUTPUT VOLTAGE (VP-P)
60
1400
150
1600
350
Input Current vs.
EL Frequency (Single EL Lamp)
EL Frequency
vs EL Resistor
100
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)
4
M9999-100308
(408) 955-1690
Micrel
MIC4833
Functional Diagram
220µH
VDD
SW
CS
VCS
2.2nF
VDD
Output
ELA
RSW
SW
Oscillator
SW
Driver
VREF
Driver
PGND
PGND
VCS
VSENSE
Output
COM
Driver
REL
Driver Logic
&
PWM Dimming
EL
Oscillator
PGND
VCS
VDD
0
VDD
ENA
EL-A Enable
ENB
EL-B Enable
0
SLEW
Output
ELB
Driver
Output
Wave-Shaping
PGND
PGND
GND
GND
Figure 1. MIC4833 Block Diagram
October 2008
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M9999-100308
(408) 955-1690
Micrel
MIC4833
Functional Description
Overview
The MIC4833 is a high-voltage dual output EL driver
with a peak-to-peak AC output voltage of 220V
capable of driving two 4 in2 EL panels. The MIC4833
drives EL panels by converting a low DC input
voltage to a 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 MIC4833 is typically
152µA. The high voltage EL driver has two internal
oscillators to control the boost switching frequency
and the H-bridge driver frequency. Both of the
internal oscillators’ frequencies can be individually
programmed through external resistors to maximize
efficiency and brightness of the EL panel. The
MIC4833 can be dimmed using a PWM signal
applied to the REL pin with an external capacitor. An
external resistor can be used to adjust the internal
wave shaping circuit to reduce audible noise.
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 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 MIC4833 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.
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) =
46
R SW (MΩ )
EL Frequency
The EL panel frequency is controlled via an external
resistor (REL) connected between REL and VDD.
The panel frequency increases as the resistor value
decreases. In general, as the EL panel frequency
increases, the amount of current drawn from the
battery will increase. The EL panel brightness is
dependent upon its frequency. For resistor value
selections, see the “Typical Characteristics: EL
Frequency vs. EL Resistor” graph on Page 4 or use
the equation below. The EL panel frequency range
is 100Hz to 1500Hz, with an accuracy of ±20%.
( )
fEL Hz =
425
( )
R EL MΩ
Enable Function
There are a few different ways to enable and disable
the MIC4833. 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 EL panels can also be turned off by
pulling the REL resistor to ground. Although this turns
off the H-Bridge and the EL panels, the MIC4833
boost regulator will continue regulate. For individual
panel control, the ENA and ENB pins can be used to
enable ELA and ELB, respectively. Pulling ENA or
ENB high or low will turn ELA and ELB panels on or
off.
Switching Frequency
The switching frequency of the converter is
controlled via an external resistor (RSW) between
October 2008
6
M9999-100308
(408) 955-1690
Micrel
MIC4833
Figure 2. 150Hz Output Waveform
PWM Dimming
The MIC4833 may be dimmed by adding a shunt
capacitor (CPWM) to the REL pin, shown in Figure 5.
The duty cycle of the PWM signal changes the
frequency of the EL panel, thereby changing its
brightness. Increasing the PWM duty cycle
increases the EL frequency to a maximum set by
REL (Duty Cycle = 100%). Decreasing the PWM duty
cycle decreases the EL frequency. The PWM duty
cycle should not be lowered to a level that may
cause the EL frequency to be lower than 100Hz,
since EL frequencies lower than 100Hz may cause
the panel to flicker. The frequency of the PWM
signal can range from 500Hz to 50kHz. The peak
voltage of the PWM signal should be equal to VDD.
VDD
REL
REL pin
0V
PWM
1kHz
CPWM
0.01µF
Figure 5. PWM Dimming Circuit
Figure 3. 250Hz Output Waveform
Slew Resistor
The MIC4833 is designed to reduce audible noise in
EL panels by the use of the internal wave-shaping
circuit. To further reduce audible noise, a Slew
Resistor (RSLEW) can be added to limit the rate of
change of the EL driver output voltage by limiting the
output current. A slower rate of change in voltage
across the EL panel creates less physical distortion
in the material and therefore reduces the amount of
audible noise. The lower the ISLEW, the slower the
output voltage across the EL panel will change. If
RSLEW is not used, the ISLEW is by default 5mA,
equivalent to using a 22kΩ for RSLEW.
Figure 4. 350Hz Output Waveform
RSLEW
ISLEW
Open
5mA
125kΩ
1mA
22kΩ
5mA
10kΩ
10mA
Table 1. Slew Resistor Setting
October 2008
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M9999-100308
(408) 955-1690
Micrel
Application Information
The MIC4833 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 (VLS4012T-221M) 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 (2.3 to 3V), a
lower value inductor, such as 100µH, may be used
in order to drive the EL panel at maximum
brightness.
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.
October 2008
MIC4833
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 MIC4833 circuit. Selection of the capacitor value
depends upon the peak inductor current, inductor
size, and the load. The MIC4833 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 capacitance at 200V to
250V voltage rating in 0805 size.
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
determined by REL. The alternating 220V peak-topeak 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 8in2
(For example, two 4in2 panels). Driving overly large
panels will result in a dimmer display, but will not
cause damage to the device.
8
M9999-100308
(408) 955-1690
Micrel
MIC4833
Application Circuit
High
Low
VIN
Li Ion
3V to 4.2V
RSW
332k
C1
0.01µF
REL
1.78M
High
Low
RSLEW
50k
ENA
SLEW
VDD
ELA
EL Lamp A
ELB
EL Lamp B
RSW
MIC4833
REL
COM
ENB
CS
GND
SW
High
Low
L1
220µH
VIN
Li Ion
3V to 4.2V
C3
2.2nF
250V
C2
10µF
Figure 6: Typical Li-Ion Powered MIC4833 Circuit
Note: Table 2 applies to circuit shown in Figure 6.
Total
Panel
Area
2
(inch )
Capacitance
(nF)
0.4
2
1
5
2
10
3
15
4
20
5
25
6
30
8
40
Panel
Frequency
(Hz)
REL (MΩ)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
RSW (kΩ)
fSW (kHz)
150
200
250
300
350
400
500
2.80
324
138
357
125
402
112
464
98
523
86
619
72
698
65
1000
45
2.10
340
132
365
122
453
100
511
88
665
68
825
55
953
47
1.69
357
126
392
116
487
92
590
77
750
60
909
50
1000
45
1.40
383
118
422
108
549
83
698
65
909
50
1000
45
1.21
392
116
442
102
590
76
768
58
1000
45
1.05
402
112
475
95
649
70
909
50
1000
45
.850
442
102
511
88
681
66
1000
45
Table 2: Recommended RSW & REL Values For Total Panel Sizes
October 2008
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M9999-100308
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Micrel
MIC4833
Bill of Materials
Item
Part Number
Manufacturer
C1
C1608X7R1A103K
TDK(1)
C1608X5R0J106K
C2
C3
C2012C0G2E2222J
L1
VLS4012T-221M
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
(2)
D1
BAS20-V-GS18
Vishay
200V/200mA Hi-Voltage Switching Diode
1
R1 or RSW
CRCW06033323FKEYE3
Vishay(2)
332kΩ, 1%, 1/16W, Size 0603
1
CRCW06031784FKEYE3
(2)
Vishay
1.78MΩ, 1%, 1/16W, Size 0603
1
Micrel(3)
Low Noise Dual 220Vp-p EL Driver with Output Slew Control
R2 or REL
RSLEW
Optional
U1
MIC4833YML
1
Notes:
1.
TDK: www.tdk.com
2.
Vishay: www.vishay.com
3.
Micrel, Inc.: www.micrel.com
October 2008
10
M9999-100308
(408) 955-1690
Micrel
MIC4833
Layout Recommendation
Top Layer
Bottom Layer
October 2008
11
M9999-100308
(408) 955-1690
Micrel
MIC4833
Package Information
12-Pin 3mm x 3mm MLF® (ML)
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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M9999-100308
(408) 955-1690