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參數資料
| 型號： | FAN7544N |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩壓器 |
| 英文描述： | Terminal Block; RoHS Compliant:Yes RoHS Compliant: Yes |
| 中文描述： | 0.6 A FLUORESCENT LIGHT CONTROLLER, 54.5 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | DIP-8 |
| 文件頁數： | 8/14頁 |
| 文件大小： | 1185K |
| 代理商： | FAN7544N |
FAN7544
8
Operating Mode
The FAN7544 has three operating mode as was shown in the figure 12.
1) Preheating Mode
The preheating mode is defined as the IC’s internal status is in when the lamp filaments are being heated to correct emission
temperature. This is necessary for maximizing lamp life and reducing the required ignition voltage. As soon as the Vcc
exceeds the UVLO high threshold , the preheating time set-up capacitor, CPH starts to be charged by the internal 1.6
μ
A cur-
rent source until the V
CPH
reaches 2.9V. From 0V to 2.9V of the V
CPH
after the V
CPH
start to be charged, the switching fre-
quency throughout the preheating mode is determined by CT and RPH and the preheating time is decided by the CPH and the
1.6
μ
A current source. (
T
PRE
=CPH
×2.9
V/1.6
μ
A)
2) Ignition mode
The ignition mode is defined as the IC’s internal status is in when a high voltage is established across the lamp necessary for
igniting the lamp. When the V
CPH
exceeds 2.9V, the FAN7544 enters the ignition mode, and moves to the run mode when the
V
CPH
exceeds 5V. In this period
,
the internal 10
μ
A current source charges the external preheating timing capacitor(CPH) in
order to increase noise immunity with sharp slop of the V
CPH
. The ignition time is decided CPH and internal 10
μ
A current
source(
T
IGN
=CPH
×
V
CPH2
/I
CPHH
). In this mode, the switching frequency is determined by CT, RPH and RT because the
I
CT
is decided by the following equation.
3) Run Mode
After the lamp has successfully ignited, the FAN7544 enters run mode. The run mode is defined as the IC’s internal status is in
when the lamp is being driven with a normal power level after the lamp is discharged. The run mode switching frequency is
determined by the timing resistor RT and timing capacitor CT. As soon as the VCPH exceeds 5V, the protection masking mode
is disable and the IC can enter the protection mode.
Protection Mode
If the voltage at the RPH pin decreases below 2V during the run mode, the FAN7544 enters the protection mode and all gate
drive outputs(OUT1 & OUT2) are latched off in the low state and the VCPH is decreased to 0V. To exit the protection mode,
the Vcc must go down below the UVLO low threshold.
(
)
5
2 1
.
RPH
RT
CT
RT
CPH
I
I
I
I
V V
=
+
(
)(
)
(
)
)
(
0
2.9
5
2.9
5
2.9
2.9
5
5
5
2.9
;
5
i
;
CPH
PH
V
RT
V
CT
i
RT
PH
CPH
PH
V
RT
V
CT
i
RT
CPH
CPH
CT
RT
V
V
V
I
I
I
V
V
I
V
V
;Preheating Fre
V
I
I
I
V
V
Frequency Sw
V
Run Frequen
qu
V
enc
c
e p
y
y
I
<
<
=
+
=
≤
<
=
+
≥
=
Figure 12. Timing Diagram
Vcc
t
f
pre
f
run
f
ign
preheating
t
ph
ignition
t
sw
run
Vth(st)
V
CPH
2.9V
5V
f
t
t
f
run
f
pre
I
CPHL
=1.6
μ
A
I
CPHH
=10
μ
A
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