Datasheet

DS3881
Single-Channel Automotive CCFL Controller
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Table 9. Transformer Specifications (as Used in the Typical Operating Circuit )
PARAMETER CONDITIONS MIN TYP MAX UNITS
Turns Ratio (Secondary/Primary) (Notes 1, 2, 3) 40
Frequency 40 80 kHz
Output Power 6W
Output Current 58mA
Primary DCR Center tap to one end 200 mΩ
Secondary DCR 500 Ω
Primary Leakage 12 µH
Secondary Leakage 185 mH
Primary Inductance 70 µH
Secondary Inductance 500 mH
100ms minimum 2000
Secondary Output Voltage
Continuous 1000
V
RMS
Note 1: Primary should be Bifilar wound with center tap connection.
Note 2: Turns ratio is defined as secondary winding divided by the sum of both primary windings.
Note 3: 40:1 is the nominal turns ratio for driving a 438mm x 2.2mm lamp with a 12V supply. Refer to Application Note 3375 for more
information.
Table 10. Resistor and Capacitor Selection Guide
DESIGNATOR QTY VALUE
TOLERANCE
(%) AT +25°C
TEMPERATURE
COEFFICIENT
NOTES
R5, R6 1 10kΩ 1——
R3, R4 1
12.5kΩ to
105kΩ
1 — See the Setting the SVM Threshold Voltage section.
R9 1
20kΩ to
40kΩ
1 ≤153ppm/°C
2% or less total tolerance. See the Lamp Frequency
Configuration section to determine value.
R10 1
18kΩ to
45kΩ
1 ≤153ppm/°C
2% or less total tolerance. See the Lamp Frequency
Configuration section to determine value.
R1 1 4.7kΩ 5 Any grade —
R2 1 4.7kΩ 5 Any grade —
R11 1 4.7kΩ 5 Any grade —
R7 1/Chan 140Ω 1 — See the Setting the RMS Lamp Current section.
C8 1/Chan 100nF 10 X7R
C ap aci tor val ue w i l l al so affect LC M b i as vol tag e d ur i ng
p ow er - up . A l ar g er cap aci tor m ay cause a l ong er ti m e
for V
D C B
to r each i ts nor m al op er ati ng l evel .
C2 1/Chan 10pF 5 ±1000ppm/°C 2kV to 4kV breakdown voltage required.
C3 1/Chan 27nF 5 X7R
C ap aci tor val ue w i l l al so affect LC M b i as vol tag e d ur i ng
p ow er - up . A l ar g er cap aci tor m ay cause a l ong er ti m e
for V
D C B
to r each i ts nor m al op er ati ng l evel .
C1 1/Chan 33µF 20 Any grade —
C7 2/DS3881 0.1µF 10 X7R Place close to V
CC
and GND on DS3881.