MIC4826_09 Datasheet, PDF (8/12 Pages) Micrel Semiconductor – Low Input Voltage, 160VPP Output Voltage, EL Driver

MIC4826
Micrel
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 R_SW) 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
Pre-designed Application Circuits
Li-Ion Battery
V_IN
3.0V to 4.2V
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 efficiency.
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 surface-mount
package. Typically, values ranging from 0.01µF to 0.1µF at
100V can be used for the regulated boost output capacitor.
L1
220µH
D1
Murata
Vishay Telefunken
LQH4C221K04
BAV19WS
C2
10µF/6.3V
Murata
GRM42-6X5R106K6.3
C1
0.22µF/10V
Murata
GRM39X7R 224K10
R2
3.32M
MIC4826
1 _VDD
R1 _{2 RSW}
322k
3 _REL
4 _GND
SW ⁵
CS ⁶
VB ⁷
VA ⁸
C_OUT
0.01µF/100V
GRM40X7R103K
3in² LAMP
V_IN
3.3V
I_IN
20mA
V_A–V_B
160V_PP
F_EL
100Hz
Lamp Size
3in²
V_IN = 3.0V
L = 220µH�
C_OUT = 0.01µF
Lamp = 2in²ï¿½
R_SW = 332k�
R_EL = 3.32M
MIC4826
TIME (2ms/div)
Figure 5. Typical 100Hz EL Driver for 3in² Lamp
8
March 2009