CPC6826 Datasheet, PDF (11/12 Pages) Clare, Inc. – High Voltage EL Lamp Driver

CPC6826
4.5 Output Oscillator Frequency
Setting the output oscillator frequency is accomplished
by connecting an external resistor between pin 3, R_EL,
and pin 1, V_DD. The output oscillator frequency
increases as the resistor value decreases. For resistor
value selections refer to the typical characteristics
graph: Output Oscillator Frequency vs. R_EL
Resistor.
The switching frequency range is 60Hz to 1000Hz,
with an accuracy of +/- 20%. Note that higher EL
frequencies draw more current from the battery. In
addition to this, the color of the EL lamp and the light
intensity are also dependent on the frequency.
10000
CPC6826
Output Oscillator Frequency
vs. R Resistor
EL
1000
100
10
0.1
1
10
4.6 Enable/Disable Function
This function can be implemented to manually enable
or disable the CPC6826. The enable function is
accomplished by connecting resistor R_SW, on pin 2,
and resistor R_EL, on pin 3, to V_DD pin 1. To disable the
CPC6826, connect the two resistors to GND.
5. External Component Description
5.1 Diode
The application circuit lists fast-reverse-recovery
diodes such as the 1SS400T1G in the SOD523
package, with a breakdown voltage of 100V and a
forward current rating of 200mA. The typical voltage
drop is 950mV at 25°C and the reverse recovery time,
t_RR, is 4nS.
ranging from 0.01μF to 0.1μF with a working voltage of
100V. Ceramic capacitors come in 0805 or 1206 size
with an X7R temperature coefficient. If the application
requires higher stability over temperature, use a
capacitor with a COG or NPO temperature coefficient.
5.3 Inductor
The inductor value depends on the specific application
requirements. In general, inductor values for typical
application circuits range from 100μH up to 1mH. The
smaller value inductors are well suited to drive larger
lamp sizes due to their inherent high current handling
capability. Note that when inductor value decreases,
the switching frequency controlled by R_SW should be
increased to avoid inductor saturation.
A 220μH Murata (LQH43MN221K03) inductor with
5.4-Ohm series DC resistance, 110mA rated current,
and +/- 10% tolerance is recommended. For inductors
with the same value and lower series DC resistance,
R_SW may have to be adjusted to avoid saturation.
Murata offers the LQH43 series from 100μH to 560μH
in the 1812 package size.
5.4 R_EL Resistor
The EL lamp frequency is controlled via an external
resistor connected from pin 3, R_EL-osc, to pin 1, V_DD.
The lamp frequency increases as the value of R_EL
decreases. Higher EL frequency will increase the
current that is drawn from the battery and will
decrease the voltage at pin 6, V_CS. The color of the
Lamp also depends on its frequency. The size of the
resistor used in the application is 0603 with a
tolerance of 1%. Smaller size resistors can be used to
reduce board space consumed.
5.5 R_SW Resistor
The switching frequency of the converter is set by
adjusting the value of resistor, R_SW, which is
connected between pin 2 and pin 1, V_DD. The
switching frequency increases as R_SW decreases.
Increasing the value of Rsw will decrease the
switching frequency of the internal oscillator, which in
turn decrease inductor current and V_CS voltage at pin
6. The size of the resistor used in the application is
0603 with a tolerance of 1%. Smaller size resistors
can be used to reduce board space consumed.
5.2 Output Capacitor
The value of the output capacitor, C_OUT, connected to
pin 6, is based on the particular application circuit and
is dependent on peak inductor current, inductor size,
and the load. The application circuits give values
R00C
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