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Linear Technology Electronic Components Datasheet

LT1508 Datasheet

Power Factor and PWM Controller(Voltage Mode)

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FEATURES
s PFC and PWM Single Chip Solution
s Synchronized Operation up to 300kHz
s 99% Power Factor Over 20:1 Load Current Range
s Voltage Mode PWM
s Instantaneous Overvoltage Protection
s Dedicated Overvoltage Protection (OVP Pin)
s Minimal Line Current Dead Zone
s Typical 250µA Start-Up Supply Current
s Line Switching Noise Filter
s Low Quiescent Current: 13mA
s Fast 1.5A Peak Current Gate Drivers
s Separate Soft Start Control
U
APPLICATIONS
s Universal Power Factor Corrected Power Supplies
and Preregulators
LT1508
Power Factor and PWM
Controller (Voltage Mode)
DESCRIPTION
The LT ®1508 is a complete solution for universal off-line
switching power supplies utilizing active power factor
correction. The PFC section is identical to the LT1248 PFC
controller except the EN/SYNC pin is removed because
PFC and PWM are synchronized internally.
The voltage mode PWM section (LT1509 is the current
mode counterpart) contains all the primary side functions
to convert the PFC preregulated high voltage output to an
isolated low voltage output. The PWM duty cycle is
internally limited to 47% (maximum 50%) to prevent
transformer saturation. PWM soft start begins when the
PFC output reaches the preset voltage. In the event of brief
line loss, PWM will be shut off when the PFC output
voltage drops below 73% of the preset value.
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRAM
VCC
16V TO 10V
VSENSE
14
7.5V
IAC
9
7.9V
OVP
11
SS1 14µA
16
14µA
SS2
13
+
EA
+
+
VAOUT
10
7.5V
VREF
VREF
12
MOUT ISENSE
87
RUN
2.2V +
M1
IA
25k
IB
IM =
IA2IB
200µA2
7µA
IM
CA
+
R
2R
+
PWMOK
+
1V
7V TO
4.7V
CL
+
+
NOTE: PWM PULSE IS DELAYED BY 55% DUTY CYCLE
AFTER PFC PULSE
19 ILIM
VC 18 50µA
CAOUT
6
GND1
3
+
+
0.7V
R
R
RUN S
Q
OSC
4 CSET
RSET 15
55%
DELAY
S
RQ
R
200ns
BLANKING
PKLIM VCC
5 17
+
GTDR1
1
16V
GND2
2
GTDR2
20
16V
1508 BD
1


Linear Technology Electronic Components Datasheet

LT1508 Datasheet

Power Factor and PWM Controller(Voltage Mode)

No Preview Available !

LT1508
DESCRIPTION
By using fixed high frequency PWM current averaging
without the need for slope compensation, the LT1508
achieves far lower line current distortion with a smaller
magnetic element than systems that use either peak
current detection, or zero current switching approach, in
both continuous and discontinuous modes of operation.
The LT1508 also provides filtering capability to reject line
switching noise which can cause instability when fed into
the multiplier. Line current dead zone is minimized with
low bias voltage at the current input to the multiplier. The
LT1508 provides many protection features including peak
current limiting and overvoltage protection. Implemented
with a very high speed process, the LT1508 can be
operated at frequencies as high as 300kHz.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage ........................................................ 27V
GTDR Current Continuous ...................................... 0.5A
GTDR Output Energy ................................................ 5µJ
IAC, RSET, PKLIM Input Current .............................. 20mA
VSENSE, OVP Input Voltage .................................... VMAX
ILIM, VC Input Voltage ................................................ 8V
ISENSE, MOUT Input Current ................................... ±5mA
Operating Junction Temperature Range
LT1508C ................................................ 0°C to 100°C
LT1508I ............................................ – 40°C to 125°C
Thermal Resistance (Junction-to-Ambient)
N Package ................................................... 100°C/W
SW Package ................................................ 120°C/W
PACKAGE/ORDER INFORMATION
TOP VIEW
GTDR1 1
GND2 2
GND1 3
CSET 4
PKLIM 5
CAOUT 6
ISENSE 7
MOUT 8
IAC 9
VAOUT 10
20 GTDR2
19 ILIM
18 VC
17 VCC
16 SS1
15 RSET
14 VSENSE
13 SS2
12 VREF
11 OVP
N PACKAGE
20-LEAD PDIP
SW PACKAGE
20-LEAD PLASTIC SO WIDE
TJMAX = 125°C, θJA = 100°C/ W (N)
TJMAX = 125°C, θJA = 120°C/ W (SW)
Consult factory for Military grade parts.
ORDER PART
NUMBER
LT1508CN
LT1508CSW
LT1508IN
LT1508ISW
ELECTRICAL CHARACTERISTICS
Maximum operating voltage (VMAX) = 25V, VCC = 18V, RSET = 15k to GND, CSET = 1nF to GND, IAC = 100µA, ISENSE = 0V, CAOUT = 3.5V,
VAOUT = 5V, OVP = VREF. No load on any outputs unless otherwise noted.
PARAMETER
Overall
Supply Current (VCC in Undervoltage Lockout)
Supply Current On
VCC Turn-On Threshold (Undervoltage Lockout)
VCC Turn-Off Threshold
Voltage Amplifier (PFC Section)
Voltage Amp Offset
Input Bias Current
Voltage Gain
Voltage Amp Unity-Gain Bandwidth
Voltage Amp Output High (Internally Clamped)
Voltage Amp Output Low
Voltage Amp Short-Circuit Current
CONDITIONS
VCC = Lockout Voltage – 0.2V
11.5V VCC VMAX
VAOUT = 3.5V
VSENSE = 0V to 7V
VAOUT = 0V
MIN TYP MAX
UNITS
q 0.25 0.45
q 13 19
q 15.5 16.5 17.5
q 9.5 10.5 11.5
mA
mA
V
V
q – 10
10
q – 25 – 250
70 100
3
q 11.3 13.3
q 1.1 2
q3
8 17
mV
nA
dB
MHz
V
V
mA
2


Part Number LT1508
Description Power Factor and PWM Controller(Voltage Mode)
Maker Linear Technology
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LT1508 Datasheet PDF





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