March 2009 1 MIC4826
MIC4826 Micrel
MIC4826
Low Input Voltage, 160VPP Output Voltage, EL Driver
General Description
Micrel’s MIC4826 is a high output voltage, DC to AC converter,
designed for driving EL (Electroluminescent) lamps. The
device operates from an input voltage range of 1.8V to 5.5V,
making it suitable for 1-cell Li Ion and 2- or 3-cell alkaline/
NiCad/NiMH battery applications. The MIC4826 converts
a low voltage DC input to a 160VPP AC output signal that
drives the EL lamp.
The MIC4826 is comprised of two stages: a boost stage, and
an H-bridge, lamp driver, stage. The boost stage steps the
input voltage up to +80V. The H-bridge stage then alternately
switches the +80V output to each terminal of the EL lamp,
thus creating a 160VPP AC signal to drive the EL lamp and
generate light.
The MIC4826 features separate oscillators for the boost-
and H-bridge stages. External resistors independently set
the operating frequency of each stage. This exibility allows
the EL lamp circuit to be optimized for maximum efciency
and brightness.
The MIC4826 uses a single inductor and a minimum number
of external components, making it ideal for portable, space-
sensitive applications.
The MIC4826 is available in an 8-pin MSOP package with
an ambient temperature range of –40°C to +85°C.
Typical Application
Features
• 1.8V to 5.5V DC input voltage
• 160VPP regulated AC output waveform
• Independently adjustable EL lamp frequency
• Independently adjustable boost converter frequency
• 0.1µA shutdown current
Applications
• LCD panel backlight
• Cellular phones
• PDAs
• Pagers
• Calculators
• Remote controls
• Portable phones
Ordering Information
Part Number
Standard Pb-Free Temp. Range Package
MIC4826BMM MIC4826YMM –40°C to +85°C MSOP-8
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
High Voltage EL Driver
442k
2M
VIN
COUT
0.01µF/100V
D1
BAV19WS
L1
220µH
2in2 EL LAMP
15
6
8
7
2
3
4
SW
CS
VA
VB
VDD
RSW
REL
GND
MIC4826
CIN
10µF
TIME (2ms/div)
V
B
(50V/div)
V
A
(50V/div)
V
A
Ð
V
B
(50V/div)
V
IN
= 3.0V
L = 220µH�
C
OUT
= 0.01µF
Lamp = 2in
2
�
R
SW
= 332k�
R
EL
= 3.32M
MIC4826 Micrel
MIC4826 2 March 2009
Pin Conguration
1VDD
RSW
REL
GND
8VA
VB
CS
SW
7
6
5
2
3
4
8-Pin MSOP Package (MM)
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
power MOSFET by connecting an external resistor to VDD. Connecting the
external resistor to GND disables the switch oscillator and shutdown 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 Return.
5 SW Switch Node (Input): Internal high-voltage power MOSFET drain.
6 CS Regulated Boost Output (External Component): Connect to the output ca-
pacitor 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 the other end of the EL lamp. Polarity is not important.
March 2009 3 MIC4826
MIC4826 Micrel
Electrical Characteristics
VIN = VDD = 3.0V, RSW = 560KΩ, REL = 1.0MΩ. TA = 25°C unless otherwise specied. Bold values indicate -40°C ≤ TA ≤ +85°C
Symbol Parameter Condition Min Typ Max Units
RDS(ON) On-resistance of switching transistor ISW = 100 mA, VCS = 75V 3.8 7.0 Ω
VCS Output voltage regulation VDD = 1.8V to 5.5V 75 80 85 V
73 87 V
VA – VB Output peak-to-peak voltage VDD = 1.8V to 5.5V 150 160 170 V
146 174 V
VEN-L Input low voltage (turn off) VDD = 1.8V to 5.5V 0.5 V
VEN-H Input high voltage (turn on) VDD = 1.8V to 5.5V VDD–0.5 V
ISD Shutdown current, Note 4 R
SW = LOW; REL = LOW; 0.01 0.1 µA
V
DD = 5.5V
0.5 µA
IVDD Input supply current RSW = HIGH; REL = HIGH; 21 75 µA
V
CS = 75V; VA, VB OPEN
ICS Boosted supply current RSW = HIGH; REL = HIGH; 200 400 µA
V
CS = 75V; VA, VB OPEN
IIN Input current including inductor VIN = VDD = 1.8V 28 mA
current (See Test Circuit)
fEL VA–VB output drive frequency 285 360 435 Hz
fSW Switching transistor frequency 53 66 79 kHz
D Switching transistor duty cycle 90 %
Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended.
Note 4. Shutdown current is dened as the sum of current going into pin 1, 5, and 6 when the device is disabled.
Test Circuit
442k
2M
C
OUT
0.01µF/100V
D1
BAV19WS
L1
220µH
15
6
8
7
2
3
4
SW
CS
VA
VB
VDD
RSW
REL
GND
MIC4826
C
IN
10µF
V
IN
10nF
100Ω
Absolute Maximum Rating (Note 1)
Supply Voltage (VDD) .......................................–0.5V to +6V
Output Voltage (VCS) ...................................–0.5V to +100V
Frequency Control Voltage (VRSW, VREL)
...
–0.5V to (VDD + 0.3V)
Power Dissipation @ TA = 85°C .............................. 200mW
Storage Temperature (TS) ........................ –65°C to +150°C
ESD Rating .............................................................. Note 3
Operating Ratings (Note 2)
Supply Voltage (VDD) ........................................1.8V to 5.5V
Lamp Drive Frequency (fEL) .......................60Hz to 1000Hz
Switching Transistor Frequency (fSW) ........ 8kHz to 200kHz
Ambient Temperature (TA) .......................... –40°C to +85°C
Package Thermal Resistance
8-pin MSOP (θJA) .............................................. 206°C/W
MIC4826 Micrel
MIC4826 4 March 2009
Typical Characteristics
0
5
10
15
20
25
30
35
40
45
50
0123456
INPUT CURRENT (mA)
INPUT VOLTAGE (V)
Total Input Current
vs. Input Volta
g
e
RSW = 332k
REL = 3.32M
RSW = 442k
REL = 2M
RSW = 562k, REL = 1M
Lamp = 2in2
L = 220µH
D = BAV19WS
COUT = 0.1µF
0
5
10
15
20
25
30
35
40
45
50
-40 -20 020406080 100
INPUT CURRENT (mA)
TEMPERATURE (°C)
Total Input Current
vs. Temperature
RSW = 332k
REL = 3.32M
RSW = 442k
REL = 2M
RSW = 562k
REL = 1M
VIN = 3.0V
Lamp = 2in2
L = 220µH
D = BAV19WS
COUT = 0.1µF
0
20
40
60
80
100
120
140
160
180
200
123456
VA –VB (VPP)
INPUT VOLTAGE (V)
Output Voltage
vs. Input Volta
g
e
RSW = 332k
REL = 3.32M
RSW = 442k
REL = 2M
RSW = 562k
REL = 1M
Lamp = 2in2
L = 220µH
D = BAV19WS
COUT = 0.1µF
0
20
40
60
80
100
120
140
160
180
200
-40 -20 020406080 100
OUTPUT VOLTAGE (VPP)
TEMPERATURE (°C)
Output Voltage
vs. Temperature
VIN = 3.0V
Lamp = 2in2
L = 220µH
COUT = 0.1µF
D = BAV19WS
RSW = 332k
REL = 3.32M
RSW = 442k
REL = 2M
RSW = 562k
REL = 1M
0
10
20
30
40
50
60
70
80
90
100
-40 -20 020406080 100
VCS (VAVG)
TEMPERATURE (°C)
CS Voltage
vs. Temperature
VIN = 3.0V
Lamp = 2in2
L = 220µH
COUT = 0.1µF
D = BAV19WS
RSW = 332k
REL = 3.32M RSW = 442k
REL = 2M
RSW = 562k
REL = 1M
0
1
2
3
4
5
6
7
123456
SWITCH RESISTANCE (Ω)
INPUT VOLTAGE (V)
Switch Resistance
vs. Input Volta
g
e
10
100
1000
10000
0.1 110
EL FREQUENCY (Hz)
EL RESISTOR (MΩ)
EL Frequency
vs. EL Resistor
1
10
100
1000
100 1000 10000
SWITCHING FREQUENCY (kHz)
SWITCH RESISTOR (kΩ)
Switching Frequency
vs. Switch Resistor
0
20
40
60
80
100
120
-40 -20 020406080 100
FREQUENCY (KHz)
TEMPERATURE (°C)
Switching Frequency
vs. Temperature
RSW = 332k
VIN = 3.0V
RSW = 442k
RSW = 562k
0
20
40
60
80
100
120
123456
SWITCHING FREQUENCY (Hz)
INPUT VOLTAGE (V)
Switching Frequency
vs. Input Volta
g
e
RSW = 562k
RSW = 442k
RSW = 332k
0
10
20
30
40
50
60
70
80
90
100
123456
VCS (V)
INPUT VOLTAGE (V)
Output Voltage Regulation
vs. Input Voltage
RSW = 332k
REL = 3.32M
RSW = 442k
REL = 2M
RSW = 562k
REL = 1M
Lamp = 2in2
L = 220µH
COUT = 0.01µF
0
50
100
150
200
250
300
350
400
123456
EL FREQUENCY (Hz)
INPUT VOLTAGE (V)
EL Frequency
vs. Input Volta
g
e
REL = 1M
REL = 2M
REL = 3.32M
March 2009 5 MIC4826
MIC4826 Micrel
0
50
100
150
200
250
300
350
400
-40 -20 020406080 100
FREQUENCY (KHz)
TEMPERATURE (°C)
EL Frequency
vs. Temperature
RSW =1M
VIN = 3.0V
RSW = 2M
RSW = 3.32M
0
20
40
60
80
100
120
140
160
180
01234567
OUTPUT VOLTAGE (VPP)
LAMP SIZE (sq. in.)
Output Voltage
vs. Lamp Size
RSW = 332k
REL = 3.32M
VIN = 3.0V
L = 220µH
COUT = 0.1µF
D = BAV19WS
0
2
4
6
8
10
12
14
16
18
20
01234567
INPUT CURRENT (mA)
LAMP SIZE (sq. in.)
Total Input Current
vs. Lamp Size
RSW = 332k
REL = 3.32M
VIN = 3.0V
L = 220µH
D = BAV19WS
COUT = 0.1µF
MIC4826 Micrel
MIC4826 6 March 2009
Functional Diagram
Figure 1. MIC4826 Block Diagram
Functional Description
See “Application Information” for component selection and
pre-designed circuits.
Overview
The MIC4826 is a high voltage EL driver with an AC output
voltage of 160V peak-to-peak capable of driving EL lamps
up to 6 in2 . Input supply current for the MIC4826 is typically
21µA with a typical shutdown current of 10nA. The high voltage
EL driver has two internal oscillators to control the switching
MOSFET and the H-bridge driver. Both of the internal oscil-
lators’ frequencies can be individually programmed through
the external resistors to maximize the efciency and the
brightness of the lamps.
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 ows through the inductor and into the switch.
The switching MOSFET will typically turn on for 90% of the
switching frequency. During the on-time, energy is stored in
the inductor. When the switching MOSFET turns off, current
owing into the inductor forces the voltage across the induc-
tor 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 op-
posite states to achieve a 160V peak-to-peak AC output
signal. The external resistor that connects to the REL pin
determines the EL frequency.
TIME (2ms/div)
V
B
(50V/div)
V
A
(50V/div)
V
A
–
V
B
(50V/div)
V
IN
= 3.0V
L = 220µH
C
OUT
= 0.01µF
Lamp = 2in
2
R
SW
= 332k
R
EL
= 3.32M
Figure 2. 108Hz Typical Output Waveform
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 “Typical
Characteristics: Switching Frequency vs. Switch Resistor”
or use the equation below. The switching frequency range
is 8kHz to 200kHz, with an accuracy of ±20%.
f kHz RM
SW
SW
() ()
=Ω
36
March 2009 7 MIC4826
MIC4826 Micrel
EL Frequency
The EL lamp frequency is controlled via an external resistor
connected between REL pin and VDD pin of the device. As
the lamp frequency increases, the resistor value decreases.
For resistor value selections, see the “Typical Character-
istics: EL Frequency vs. EL Resistor” or use the equation
below. The EL frequency range is 60Hz to 1000Hz, with an
accuracy of ±20%.
fHzRM
EL
EL
() ()
=Ω
360
TIME (2ms/div)
V
B
(50V/div)
V
A
(50V/div)
V
A
–
V
B
(50V/div)
V
IN
= 3.0V
L = 220µH
C
OUT
= 0.01µF
Lamp = 2in
2
R
SW
= 562k
R
EL
= 1M
Figure 3. 180Hz 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.
TIME (2ms/div)
V
IN
= 3.0V
L = 220µH�
C
OUT
= 0.01µF�
Lamp = 2in
2
�
R
SW
= 562k�
R
EL
= 1M
VB
(50V/div)
VA
(50V/div)
VA Ð VB
(50V/div)
Figure 4. 360Hz Output Waveform
Enable Function
The enable function of the MIC4826 is implemented by switch-
ing the RSW and REL resistor between ground and VDD. When
RSW and REL are connected to ground, the switch and the
EL oscillators are disabled; therefore the EL driver becomes
disabled. When these resistors connect to VDD, both oscilla-
MIC4826 Micrel
MIC4826 8 March 2009
R1
322k
R2
3.32M
Li-Ion Battery
V
IN
3.0V to 4.2V
C1
0.22µF/10V
Murata
GRM39X7R 224K10
C
OUT
0.01µF/100V
GRM40X7R103K
D1
Vishay Telefunken
BAV19WS
L1
220µH
Murata
LQH4C221K04
3in
2
LAMP
15
6
7
8
2
3
4
SW
CS
VB
VA
VDD
RSW
REL
GND
MIC4826
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
tors will function and the EL driver is enabled.
Application Information
Inductor
In general, smaller value inductors, which can handle more
current, are more suitable to drive larger size lamps. As the
inductor value decreases, the switching frequency (controlled
by RSW) should be increased to avoid saturation or the input
voltage should be increased. Typically, inductor values ranging
from 220µH to 560µH can be used. Murata offers the LQH3C
series up to 560µH and LQH4C series up to 470µH, with low
DC resistance. A 220µH Murata (LQH4C221K04) inductor is
recommended for driving a lamp size of 3 square inches. It
has a maximum DC resistance of 4.0Ω.
Diode
The diode must have a high reverse voltage (100V) since
the output voltage at the CS pin can reach up to 100V. A
fast switching diode with lower forward voltage and higher
reverse voltage (100V), such as BAV19WS, can be used to
enhance efciency.
Output Capacitor
Low ESR capacitors should be used at the regulated boost
output (CS pin) of the MIC4826 to minimize the switching output
ripple voltage. Selection of the capacitor value will depend
upon the peak inductor current, inductor size, and the load.
MuRata offers the GRM40 series with up to 0.015µF at 100V,
with a X7R temperature coefcient in 0805 surface-mount
package. Typically, values ranging from 0.01µF to 0.1µF at
100V can be used for the regulated boost output capacitor.
Pre-designed Application Circuits
VIN I
IN V
A–VB F
EL Lamp Size
3.3V 20mA 160VPP 100Hz 3in2
TIME (2ms/div)
V
B
(50V/div)
V
A
(50V/div)
V
A
Ð
V
B
(50V/div)
V
IN
= 3.0V
L = 220µH�
C
OUT
= 0.01µF
Lamp = 2in
2
�
R
SW
= 332k�
R
EL
= 3.32M
Figure 5. Typical 100Hz EL Driver for 3in2 Lamp
March 2009 9 MIC4826
MIC4826 Micrel
VIN I
IN V
A–VB F
EL Lamp Size
3.3V 14mA 160VPP 100Hz 2in2
TIME (2ms/div)
V
B
(50V/div)
V
A
(50V/div)
V
A
Ð
V
B
(50V/div)
V
IN
= 3.0V
L = 220µH�
C
OUT
= 0.01µF
Lamp = 2in
2
�
R
SW
= 332k�
R
EL
= 3.32M
Figure 6. Typical EL Driver for 2in2 Lamp with CS = 0.1µF
R1
332k
R2
3.32M
V
IN
2.5V to 5.5V
C
OUT
0.1µF/100V
GRM42-2X7R104K100
D1
Diodes
BAV20WS
L1
220µH
Murata
LQH4C221K04
EL LAMP
LSI�
X533-13
15
6
7
8
2
3
4
SW
CS
VB
VA
VDD
RSW
REL
GND
MIC4826
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
MIC4826 Micrel
MIC4826 10 March 2009
VIN I
IN V
A–VB F
EL Lamp Size
3.3V 13.2mA 160VPP 100Hz 2in2
�
TIME (2ms/div)
V
B�
(50V/div)
V
A�
(50V/div)
V
A
–
V
B�
(50V/div)
Figure 7. Typcial EL Driver for 2in2 Lamp with 560µH inductor
R1
332k
R2
3.32M
VIN
3.3V to 5.5V
COUT
0.01µF/100V
GRM40X7R103K100
D1
Diodes
BAV20WS
L1
560µH
Murata
LQ32CN561K21
EL LAMP
LSI
X533-13
15
6
7
8
2
3
4
SW
CS
VB
VA
VDD
RSW
REL
GND
MIC4826
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
March 2009 11 MIC4826
MIC4826 Micrel
�
TIME (2ms/div)
V
B�
(50V/div)
V
A�
(50V/div)
V
A
–
V
B�
(50V/div)
Figure 8. Typical Split Power Supplies Applications
VIN I
IN V
DD IDD VA–VB F
EL Lamp Size
1.5V 22mA 3.0V 36µA 160VPP 100Hz 1.6in2
R1
442k
R2
3.32M
V
IN
1.5V
C
OUT
0.01µF/100V
GRM40X7R103K100
D1
Diodes
BAV20WS
L1
220µH
Murata
LQH4C221K04
EL LAMP
15
6
7
8
2
3
4
SW
CS
VB
VA
VDD
RSW
REL
GND
MIC4826
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
C1
0.01µF/50V
Murata
GRM40-X7R103K50
V
DD
1.8V to 5.5V
MIC4826 Micrel
MIC4826 12 March 2009
Package Information
8-Lead MSOP (MM)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
tel + 1 (408) 944-0800 fa x + 1 (408) 474-1000 w e b 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 specications at any time without notication 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 signicant 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.
© 2001 Micrel Incorporated