www.fairchildsemi.com
KA7540
Simple Dimming Ballast Control IC
Features
•
•
•
•
•
•
•
•
Internal soft start
No lamp protection
Voltage controlled dimming
Trimmed 1.5% internal bandgap reference
Under voltage lock out with 1.8V of hysteresis
Totem pole output with high state clamp
Low start-up and operating current
8-pin DIP & 8-pin SOP
Descriptions
The KA7540 provides simple and high performance
electronic ballast control functions. KA7540 is optimized for
electronic ballast requiring a minimum board area, reduced
component count and low power dissipation. Internal soft
start circuitry eliminates the need for an external soft start
PTC resistor. Voltage controlled dimming circuit is built into
the IC to control the lighting output in a wide range.
Protection circuitry has also been added to prevent switches
from burning out in no lamp condition. Output gate drive
circuit clamps power MOSFET gate voltage irrespective of
supply voltage.
8-DIP
Applications
• Electronic Ballast
• Lighting Control System
• Half-bridge Drive Control System
1
8-SOP
1
Rev. 1.0.1
©2001 Fairchild Semiconductor Corporation
KA7540
Internal Block Diagram
UVLO
2V Ref
C
S
6.8µF
25µA
V
Z
Vref
1
−
+
17µA
V
Z
I
S
UVLO
Internal
bias
1.8V
+
−
12.5V
8
V
CC
Oscillator
Ct
180pF
8Ict
2
Ict
latch +
Q
+
+
I
C
7
OUT 1
F.D
from V
CS
Vdim
3
80kΩ
Vd
20kΩ
100µA
3pF
V
CC
Id
+
−
kVref
V
Z
40kΩ
25µA
−
+
2V
Shut down signal
I
S
= 17µA
×
(Vref
−
V
SS
) / Vref
Id = 25µA
×
(Vref
−
Vd) / Vref
Frequency
divider
6
OUT 2
Ldet
4
5pF
5
GND
IC Characteristics
Parameter
Initial soft start frequency
Voltage controlled dimming
KA7540
1.33
×
normal operating frequency
1 ~ 10V
2
KA7540
Pin Assignments
C
S
1
8
V
CC
Ct
2
7
OUT1
Vdim
3
6
OUT2
Ldet
4
5
GND
(Top View)
Pin Definitions
Pin Number
1
2
3
4
5
6
7
8
Pin Name
C
S
C
T
Vdim
Ldet
GND
OUT 2
OUT 1
V
CC
Pin Function Description
Soft start capacitor connection pin. The pin voltage determines the phase of soft
start, normal and dimming mode.
Timing capacitor connection pin. The timing capacitor is charged and discharged
to generate the sawtooth waveform that determines the oscillation frequency in
the internal oscillator block.
Input to the dimming stage. The pin voltage sets the switching frequency in
dimming mode.
Input to the protection circuit. If the pin voltage is lower than 2V, the output of the
gate driver is inhibited.
The ground potential of all the pins.
The output of a high current power driver capable of driving the gate of a power
MOSFET.
The output of a high current power driver capable of driving the gate of a power
MOSFET.
The logic and control power supply connection.
3
KA7540
Absolute Maximum Ratings
Parameter
Supply voltage
Peak drive output current
Drive output clamping diodes
V
O
>V
CC
, or V
O
<−0.3
Dimming, soft start, and no lamp detection input voltage
Operating temperature range
Storage temperature range
8-DIP
Power dissipation
8-SOP
8-DIP
Thermal resistance (Junction-to-air)
8-SOP
Symbol
V
CC
I
OH
, I
OL
Iclamp
V
IN
Topr
Tstg
Pd
θja
Value
30
±300
±10
−0.3
to 6
-25 to 125
−65
to 150
0.8
0.5
100
165
Unit
V
mA
mA
V
°C
°C
W
°C/W
(-25°
125°
Absolute Maximum Ratings (-25
°
C
≤
Ta
≤
125
°
C)
Parameter
Temperature stability for reference voltage (Vref)
Temperature stability for operating frequency (fos)
Symbol
∆Vref
(Typ)
∆fos
(Typ)
Value
15
5
Unit
mV
kHz
4
KA7540
Electrical Characteristics
Unless otherwise specified, for typical values Vcc=14V, Ta=25°C, For Min/Max values Ta is the operating ambient
temperature range with -25°C
≤
Ta
≤
125°C and 14V≤ Vcc≤ 30V
Parameter
UNDER VOLTAGE LOCK OUT SECTION
Start threshold voltage
UVLO hysteresis
SUPPLY CURRENT SECTION
Start up supply current
Operating supply current
Dynamic operating supply current
REFERENCE SECTION
Reference voltage
(Note1)
Line regulation
(Note1)
Temperature stability of Vref
(Note1)
OSCILLATOR SECTION
Operating frequency
Operating dead time
Soft start frequency
Soft start time current
Soft start dead time
Dimming frequency
OUTPUT SECTION
Rising time
(Note2)
Falling time
(Note2)
Maximum output voltage
Output voltage with UVLO activated
NO LAMP PROTECTION SECTION
No lamp detect voltage
Vnd
-
1.9
2
2.1
V
tr
tf
Vomax(o)
Vomin(o)
CI=1nF
CI=1nF
V
CC
=20V
V
CC
=5V, I
O
=100µA
-
-
12
-
120
50
15
-
200
100
18
1
ns
ns
V
V
fos
tod
fss
I
SS
tsd
fd
V
SS
=3V, C
T
=470pF
V
SS
=3V, Vcc=14V
V
SS
=0V, C
T
=470pF
V
SS
=0V
V
SS
=0V, Vcc=14V
Vss=5V, Vdim=1V
44
2.4
56
17
1.8
58
50
2.9
65
25
2.3
72
56
3.4
74
33
2.8
86
kHz
µs
kHz
µA
µs
kHz
Vref
∆Vref
1
∆Vref
2
Iref=0mA, Vcc=14V
14V≤V
CC
≤25V
-25≤Ta≤125°C,
Vcc=14V
1.95
-
-
2
0.1
15
2.05
10
-
V
mV
mV
I
ST
I
CC
I
DCC
V
CC
<V
TH
(st),
Vcc=14V
Output not switching
50kHz, CI=1nF
-
-
-
0.2
6
7
0.3
10
14
mA
mA
mA
V
TH
(st)
HY(st)
V
CC
increasing
-
11.5
1.3
12.5
1.8
13.5
2.3
V
V
Symbol
Conditions
Min.
Typ.
Max.
Unit
Notes :
1. This parameter is not tested in production but tested in wafer.
2. This parameter, although guaranteed, is not 100% tested in production.
5
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