LT1249IN8 Linear Technology, LT1249IN8 Datasheet - Page 5

• Manufacturer Part Number: LT1249IN8
• Description: IC PFC CTRLR AVERAGE CURR 8DIP
• Manufacturer: Linear Technology

Specifications of LT1249IN8

• Mode: Average Current
• Frequency - Switching: 100kHz
• Current - Startup: 250µA
• Voltage - Supply: 15.5 V ~ 27 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

PIN
GND (Pin 1): Ground.
CA
that senses and forces the line current to follow the
reference signal that comes from the multiplier by com-
manding the pulse width modulator. When CA
the modulator has zero duty cycle.
M
through the 4k resistor R
across R
and it is limited to 1.1V. The noninverting input of the
current amplifier is also tied to R
TYPICAL PERFORMANCE CHARACTERISTICS
NOTE: THESE SINK CURRENT THRESHOLDS ARE
FOR OVERVOLTAGE PROTECTION FUNCTION.
OUT
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
60
50
40
30
20
10
OUT
U
0
0
–50
–75
Voltage Amp Sink Current Limits
(Threshold)
Synchronization Threshold
at CA
(Pin 3): The multiplier current goes out of this pin
FUNCTIONS
(Pin 2): This is the output of the current amplifier
–50
–25
MOUT
OUT
U
–25
0
TEMPERATURE ( C)
TEMPERATURE ( C)
is the reference voltage of the current loop
0
DOWN THRESHOLD
25
UP THRESHOLD
25
U
50
50
75
75
MOUT
W
100
100
1249 G11
. The voltage developed
MOUT
1249 G14
U
125
125
. In operation, M
–1.30
–1.25
–1.20
–1.15
–1.10
–1.05
–1.00
–0.95
–0.90
–0.2
–0.4
–0.6
–0.8
–1.0
1.2
1.0
0.8
0.6
0.4
0.2
0
–75
M
Maximum Multiplier Output
Voltage (I
OUT
OUT
–2.4
–50
is low,
Pin Characteristics
125 C
25 C
–50 C
–25
–1.2
OUT
M(MAX)
TEMPERATURE ( C)
M
OUT
0
VOLTAGE (V)
25
0
• R
is normally at negative potential and only AC signals
appear at the noninverting input of the current amplifier.
I
multiplier. It is a current input that is biased at 2V to
minimize the crossover dead zone caused by low line
voltage. A 32k resistor is in series with the current input,
so that a small external capacitor can be used to filter out
the switching noise from the high impedance lines.
VA
amplifier. The output is clamped at 12V. When the output
goes below 1.5V, the multiplier output current is zero.
AC
MOUT
50
OUT
(Pin 4): This is the AC line voltage sensing input to the
1.2
)
75
(Pin 5): This is the output of the voltage error
100
2.4
1249 G15
1249 G12
125
400
350
300
250
200
150
100
100
50
99
98
97
96
95
94
93
92
91
90
0
–50
–50
Maximum Duty Cycle
Transconductance of Current
Amplifier Over Temperature
–25
–25
0
0
TEMPERATURE ( C)
TEMPERATURE ( C)
25
25
50
50
LT1249
75
75
100
100
1249 G13
1249 G16
5
125
125