MICREL MIC4826

MIC4826
Micrel
MIC4826
Low Input Voltage, 160VPP Output Voltage, EL Driver
Final Information
General Description
Features
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 flexibility allows the
EL lamp circuit to be optimized for maximum efficiency and
brightness.
The MIC4826 uses a single inductor and a minimum number
of external components, making it ideal for portable, spacesensitive applications.
The MIC4826 is available in an 8-pin MSOP package with an
ambient temperature range of –40°C to +85°C.
•
•
•
•
•
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
Typical Application
1
VDD
SW
5
442k
2
RSW
CS
6
2M
3
REL
VA
8
4
GND
VB
7
VB
(50V/div)
COUT
0.01µF/100V
MIC4826
VA — VB
(50V/div)
CIN
10µF
D1
1N4148
VA
(50V/div)
L1
220µH
VIN
2in2 EL LAMP
TIME (2ms/div)
High Voltage EL Driver
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000• http://www.micrel.com
August 2004
1
MIC4826
MIC4826
Micrel
Pin Configuration
VDD 1
8 VA
RSW 2
7 VB
REL 3
6 CS
GND 4
5 SW
8-Pin MSOP Package (MM)
Pin Description
Pin Number
Pin Name
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
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 the other end of the EL lamp. Polarity is not important.
MIC4826
Pin Function
2
August 2004
MIC4826
Micrel
Absolute Maximum Rating (Note 1)
Operating Ratings (Note 2)
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
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
Electrical Characteristics
VIN = VDD = 3.0V, RSW = 560KΩ, REL = 1.0MΩ. TA = 25°C unless otherwise specified. Bold values indicate -40°C ≤ TA ≤ +85°C
Symbol
Parameter
Condition
Min
RDS(ON)
On-resistance of switching transistor
ISW = 100 mA, VCS = 75V
VCS
Output voltage regulation
VDD = 1.8V to 5.5V
75
Typ
Max
Units
3.8
7.0
Ω
80
85
V
87
V
170
V
174
V
0.5
V
73
VA – VB
Output peak-to-peak voltage
VDD = 1.8V to 5.5V
150
160
146
VEN-L
Input low voltage (turn off)
VDD = 1.8V to 5.5V
VEN-H
Input high voltage (turn on)
VDD = 1.8V to 5.5V
ISD
Shutdown current, Note 4
RSW = LOW; REL = LOW;
VDD–0.5
V
0.01
VDD = 5.5V
0.1
µA
0.5
µA
IVDD
Input supply current
RSW = HIGH; REL = HIGH;
VCS = 75V; VA, VB OPEN
21
75
µA
ICS
Boosted supply current
RSW = HIGH; REL = HIGH;
VCS = 75V; VA, VB OPEN
200
400
µA
IIN
Input current including inductor
current
VIN = VDD = 1.8V
(See Test Circuit)
28
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 defined as the sum of current going into pin 1, 5, and 6 when the device is disabled.
mA
%
Test Circuit
L1
220µH
VIN
COUT
0.01µF/100V
MIC4826
CIN
10µF
442k
2M
August 2004
D1
1N4148
1
VDD
SW
5
2
RSW
CS
6
3
REL
VA
8
4
GND
VB
7
3
100Ω
10nF
MIC4826
MIC4826
Micrel
Typical Characteristics
Total Input Current
vs. Input Voltage
Total Input Current
vs. Temperature
50
= 562k, R
EL
= 1M
RSW = 442k
15
10
5
0
0
= 2M
RSW = 332k
REL = 3.32M
Lamp = 2in2
L = 220µH
D = BAV19WS
C
= 0.1µF
OUT
1
2
3
4
5
INPUT VOLTAGE (V)
6
25
20
VIN = 3.0V
15
Lamp = 2in2
10 R = 332k
SW
L = 220µH
D = BAV19WS
5 REL = 3.32M
COUT = 0.1µF
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
Output Voltage
vs. Temperature
VCS (VAVG)
OUTPUT VOLTAGE (VPP)
70
60
50
40
20
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
10
0
1
Switch Resistance
vs. Input Voltage
SWITCHING FREQUENCY (kHz)
SWITCH RESISTANCE (Ω)
6
5
4
3
2
1
0
1
2
3
4
5
INPUT VOLTAGE (V)
6
EL FREQUENCY (Hz)
SWITCHING FREQUENCY (Hz)
RSW = 442k
RSW = 562k
20
Lamp = 2in2
L = 220µH
COUT = 0.1µF
D = BAV19WS
1000
100
10
0.1
1000
10000
SWITCH RESISTOR (kΩ)
1
EL RESISTOR (MΩ)
10
Switching Frequency
vs. Temperature
120
300
REL = 1M
250
REL = 2M
200
150
100
0
1
VIN = 3.0V
10000
REL = 3.32M
50
6
REL = 1M
RSW = 442k
REL = 2M
EL Frequency
vs. EL Resistor
350
RSW = 332k
2
3
4
5
INPUT VOLTAGE (V)
SW
EL Frequency
vs. Input Voltage
40
MIC4826
6
10
1
100
6
10
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
400
60
0
1
2
3
4
5
INPUT VOLTAGE (V)
70 R = 332k
SW
60 REL = 3.32M
50
40
R = 562k
30
20
Lamp = 2in2
L = 220µH
COUT = 0.1µF
D = BAV19WS
100
Switching Frequency
vs. Input Voltage
80
RSW = 332k
REL = 3.32M
1000
120
100
RSW = 562k
REL = 1M
Switching Frequency
vs. Switch Resistor
7
OUT
2
3
4
5
INPUT VOLTAGE (V)
90
80
30
20
Lamp = 2in2
L = 220µH
COUT = 0.1µF
D = BAV19WS
Lamp = 2in2
L = 220µH
D = BAV19WS
C
= 0.1µF
100
R =442k
90 SW
REL = 2M
80
140 R = 332k
RSW = 442k
SW
120 R = 3.32M
REL = 2M
EL
100
RSW = 562k
80
VIN = 3.0V
REL = 1M
60
40
60
40
CS Voltage
vs. Temperature
100
180
160
RSW = 562k
REL = 1M
100 R = 332k
SW
80 REL = 3.32M
CS Voltage
vs. Input Voltage
200
= 442k
140
120
20
0
1
VCS (VAVG)
25
20
EL
RSW = 442k
REL = 2M
35
30
R
180 RSW= 2M
EL
160
EL FREQUENCY (Hz)
R
200
R = 562k
45 SW
REL = 1M
40
FREQUENCY (KHz)
35
30
SW
VA –VB (VPP)
R
45
40
INPUT CURRENT (mA)
INPUT CURRENT (mA)
50
Output Voltage
vs. Input Voltage
2
3
4
5
INPUT VOLTAGE (V)
4
100
80
60
RSW = 332k
RSW = 442k
RSW = 562k
40
20
VIN = 3.0V
6
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
August 2004
MIC4826
Micrel
EL Frequency
vs. Temperature
Output Voltage
vs. Lamp Size
250
RSW = 2M
200
150
100
50
RSW = 3.32M
VIN = 3.0V
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
August 2004
20
160
140
120
INPUT CURRENT (mA)
300
RSW =1M
OUTPUT VOLTAGE (VPP)
FREQUENCY (KHz)
350
Total Input Current
vs. Lamp Size
180
400
RSW = 332k
REL = 3.32M
100
80
60
VIN = 3.0V
L = 220µH
COUT = 0.1µF
D = BAV19WS
40
20
0
0
1
2
3
4
5
6
LAMP SIZE (sq. in.)
5
7
18
16
RSW = 332k
REL = 3.32M
14
12
10
8
VIN = 3.0V
L = 220µH
D = BAV19WS
COUT = 0.1µF
6
4
2
0
0
1
2
3
4
5
6
LAMP SIZE (sq. in.)
7
MIC4826
MIC4826
Micrel
Functional Diagram
L1
220µH
VIN
1
D1
VDD
5
RSW
CIN
SW
2
RWS
Switch
Oscillator
COUT
6
CS
Q1
8
REL
VA
Q2
EL
Oscillator
VREF
EL LAMP
Q3
7
VB
3
Q4
REL
4
GND
Figure 1. MIC4826 Block Diagram
When the EL oscillator is enabled, VA and VB switch in
opposite states to achieve a 160V peak-to-peak AC output
signal. The external resistor that connects to the REL pin
determines the EL frequency.
Functional Description
MIC4826
VA
(50V/div)
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 oscillators’ frequencies can be individually programmed through
the external resistors to maximize the efficiency 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 flows 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 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.
VA — VB
(50V/div)
VB
(50V/div)
VIN = 3.0V
L = 220µH
COUT = 0.01µF
Lamp = 2in2
RSW = 332k
REL = 3.32M
TIME (2ms/div)
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%.
fSW (kHz) =
6
36
RSW (MΩ)
August 2004
MIC4826
Micrel
VA — VB
(50V/div)
VIN = 3.0V
L = 220µH
COUT = 0.01µF
Lamp = 2in2
RSW = 442k
REL = 2M
VB
(50V/div)
VIN = 3.0V
L = 220µH
COUT = 0.01µF
Lamp = 2in2
RSW = 562k
REL = 1M
VB
(50V/div)
360
REL (MΩ)
VA
(50V/div)
fEL (Hz) =
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)
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
Characteristics: EL Frequency vs. EL Resistor” or use the
equation below. The EL frequency range is 60Hz to 1000Hz,
with an accuracy of ±20%.
TIME (2ms/div)
Figure 4. 360Hz Output Waveform
VA — VB
(50V/div)
Enable Function
The enable function of the MIC4826 is implemented by
switching 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
oscillators will function and the EL driver is enabled.
TIME (2ms/div)
Figure 3. 180Hz Output Waveform
August 2004
7
MIC4826
MIC4826
Micrel
Diode
The application circuit specifies 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
BAV19WS and BAV20WS.
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 coefficient in 0805 surfacemount package. Typically, values ranging from 0.01µF to
0.1µF at 100V can be used for the regulated boost output
capacitor.
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.
Pre-designed Application Circuits
L1
D1
220µH
Vishay Telefunken
Murata
MCL4148
LQH4C221K04
Li-Ion Battery
VIN
3.0V to 4.2V
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
COUT
0.01µF/100V
GRM40X7R103K
MIC4826
C1
0.22µF/10V
Murata
GRM39X7R 224K10
R2
3.32M
R1
322k
1
VDD
SW
5
2
RSW
CS
6
3
REL
VB
7
4
GND
VA
8
3in2 LAMP
IIN
VA–VB
FEL
Lamp Size
3.3V
20mA
160VPP
100Hz
3in2
VA — VB
(50V/div)
VB
(50V/div)
VA
(50V/div)
VIN
TIME (2ms/div)
Figure 5. Typical 100Hz EL Driver for 3in2 Lamp
MIC4826
8
August 2004
MIC4826
Micrel
L1
220µH
Murata
LQH4C221K04
VIN
2.5V to 5.5V
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
D1
Diodes
BAV20WS
COUT
0.1µF/100V
GRM42-2X7R104K100
MIC4826
R1
R2
3.32M
332k
1
VDD
SW
5
2
RSW
CS
6
3
REL
VB
7
4
GND
VA
8
EL LAMP
LSI
X533-13
IIN
VA–VB
FEL
Lamp Size
3.3V
14mA
160VPP
100Hz
2in2
VA — VB
(50V/div)
VB
(50V/div)
VA
(50V/div)
VIN
TIME (2ms/div)
Figure 6. Typical EL Driver for 2in2 Lamp with CS = 0.1µF
August 2004
9
MIC4826
MIC4826
Micrel
L1
560µH
Murata
LQ32CN561K21
VIN
3.3V to 5.5V
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
D1
Diodes
BAV20WS
COUT
0.01µF/100V
GRM40X7R103K100
MIC4826
R2
3.32M
R1
332k
1
VDD
SW
5
2
RSW
CS
6
3
REL
VB
7
4
GND
VA
8
EL LAMP
LSI
X533-13
IIN
VA–VB
FEL
Lamp Size
3.3V
13.2mA
160VPP
100Hz
2in2
VA — VB
(50V/div)
VB
(50V/div)
VA
(50V/div)
VIN
TIME (2ms/div)
Figure 7. Typcial EL Driver for 2in2 Lamp with 560µH inductor
MIC4826
10
August 2004
MIC4826
Micrel
L1
220µH
Murata
LQH4C221K04
VIN
1.5V
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
VDD
1.8V to 5.5V
R1
C1
0.01µF/50V
Murata
GRM40-X7R103K50
442k
R2
3.32M
D1
Diodes
BAV20WS
COUT
0.01µF/100V
GRM40X7R103K100
MIC4826
1
VDD
SW
5
2
RSW
CS
6
3
REL
VB
7
4
GND
VA
8
EL LAMP
IIN
VDD
IDD
VA–VB
FEL
Lamp Size
1.5V
22mA
3.0V
36µA
160VPP
100Hz
1.6in2
VA — VB
(50V/div)
VB
(50V/div)
VA
(50V/div)
VIN
TIME (2ms/div)
Figure 8. Typical Split Power Supplies Applications
August 2004
11
MIC4826
MIC4826
Micrel
Package Information
0.199 (5.05)
0.187 (4.74)
0.122 (3.10)
0.112 (2.84)
DIMENSIONS:
INCH (MM)
0.120 (3.05)
0.116 (2.95)
0.036 (0.90)
0.032 (0.81)
0.043 (1.09)
0.038 (0.97)
0.012 (0.30) R
0.012 (0.3)
0.0256 (0.65) TYP
0.008 (0.20)
0.004 (0.10)
5° MAX
0° MIN
0.007 (0.18)
0.005 (0.13)
0.012 (0.03) R
0.039 (0.99)
0.035 (0.89)
0.021 (0.53)
8-Lead MSOP (MM)
MICREL INC. 1849 FORTUNE DRIVE
TEL
+ 1 (408) 944-0800
FAX
SAN JOSE, CA 95131
+ 1 (408) 474-1000
WEB
USA
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 2004 Micrel Incorporated
MIC4826
12
August 2004