Linear Technology LT1249 Datasheet

FEATURES

LT1249

Power Factor Controller

U

DESCRIPTIO

■

Standard 8-Pin Packages

■

High Power Factor Over Wide Load Range
with Line Current Averaging

■

International Operation Without Switches

■

Instantaneous Overvoltage Protection

■

Minimal Line Current Dead Zone

■

Typical 250µA Start-Up Supply Current

■

Rejects Line Switching Noise

■

Synchronization Capability

■

Low Quiescent Current: 9mA

■

Fast 1.5A Peak Current Gate Driver

U

APPLICATIO S

■

Universal Power Factor Corrected Power Supplies

■

Preregulators up to 1500W

, LTC and LT are registered trademarks of Linear Technology Corporation.

The 8-pin LT®1249 provides active power factor correc­tion for universal offline power systems with very few
external parts. By using fixed high frequency PWM current
averaging without the need for slope compensation, the
LT1249 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 LT1249 uses a multiplier containing a square gain
function from the voltage amplifier to reduce the AC gain
at light output load and thus maintains low line current
distortion and high system stability. The LT1249 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 LT1249 provides many protection features including
peak current limiting and overvoltage protection. The
switching frequency is internally set at 100kHz.

While the LT1249 simplifies PFC design with minimal
parts count, the LT1248 provides flexibilities in switching
frequency, overvoltage and current limit.

BLOCK DIAGRA

VA

OUT

5

+

7.5V

V

SENSE

6

I

AC

4

EA

–

W

44µA
22µA

MOUT

250µA MAX

+

CA

–

= 1/3k

g

m

CA

OUT

16V/10V

+

–

GND

1

7.5V
V

REF

+

V

CC

–

–

+

+

0.7V

SYNC

RUN

OSC

R
S

20µA

35pF

RUN

Q

16V

M

OUT

32

R
4k

I

A

MULTIPLIER

32k

I

IM =

B

1V

200µA

+

M1

–

I

M

2

I

I

A

B

2

15µA

4k

V

CC

7

GTDR

8

1249 BD

1

LT1249

WW

W

U

ABSOLUTE MAXIMUM RATINGS

Supply Voltage ....................................................... 27V

GTDR Current Continuous ..................................... 0.5A

GTDR Output Energy (Per Cycle) ............................. 5µJ

IAC Input Current ................................................. 20mA

V
M
Operating Junction Temperature Range

Thermal Resistance (Junction-to-Ambient)

Storage Temperature Range ..................–65°C to 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

ELECTRICAL CHARACTERISTICS

range, otherwise specifications are at T
VA

Input Voltage ............................................ V

SENSE

Input Current.............................................. ±5mA

OUT

LT1249C................................................ 0°C to 100°C

LT1249I ........................................... –40°C to 125°C

N8 Package ................................................ 100°C/W

S8 Package................................................. 120°C/W

The ● denotes specifications which apply over the operating temperature

= 25°C. Maximum operating voltage (V

= 5V, no load on any outputs, unless otherwise noted.

OUT

A

MAX

U

W

PACKAGE/ORDER INFORMATION

ORDER PART

TOP VIEW

GND

1

CA

2

OUT

M

3

OUT

I

4

AC

N8 PACKAGE
8-LEAD PDIP

S8 PACKAGE

8-LEAD PLASTIC SO

T

= 125°C, θJA = 100°C/W (N8)

JMAX

T

= 125°C, θJA = 120°C/W (S8)

JMAX

Consult factory for Military grade parts.

) = 25V, VCC = 18V, I

MAX

GTDR

8

V

7

CC

V

6

SENSE

VA

5

OUT

= 100µA, CA

AC

NUMBER

LT1249CN8
LT1249IN8
LT1249CS8
LT1249IS8

S8 PART

MARKING

1249
1249I

= 3.5V,

OUT

U

PARAMETER CONDITIONS MIN TYP MAX UNITS
Overall

Supply Current (VCC in Undervoltage Lockout) VCC = Lockout Voltage – 0.2V ● 0.25 0.45 mA
Supply Current, On 11.5V ≤ VCC ≤ V
VCC Turn-On Threshold ● 15.5 16.5 17.5 V
VCC Turn-Off Threshold ● 9.5 10.5 11.5 V

Voltage Amplifier

V

Bias Current V

SENSE

Voltage Amp Gain 70 100 dB
Voltage Amp Unity-Gain Bandwidth 1.5 MHz
Voltage Amp Output High 0 ≤ Source Current ≤ 50µA ● 10 12 V
Voltage Amp Output Low 0 ≤ Sink Current ≤ 5µA ● 0.1 0.4 V
Voltage Amp Source Current ● 130 260 450 µA
Voltage Amp Sink Current Threshold Linear Operation, 2V < VA
Voltage Amp Sink Current Hysteresis 2V < VA

Current Amplifier

Current Amp Offset Voltage ● ±2 ±15 mV
Current Amp Transconductance ∆I
Current Amp Voltage Gain 2.5V ≤ V
Current Amp Source Current V
Current Amp Sink Current V
Current Amp Output High 7.4 8.1 V
Current Amp Output Low 1.2 2 V

= 0V to 7V ● –25 –250 nA

SENSE

OUT

= ±40µA ● 150 320 550 µmho

CAOUT

CAOUT

= 1V, IM = 0µV 100 145 220 µA

MOUT

= –0.3V, IM = 0µA 67 95 125 µA

MOUT

, CA

MAX

< 10V ● 14 22.5 30 µA

≤ 7.5V 500 1000 V/V

= 1V ● 812 mA

OUT

< 10V ● 33 44 57 µA

OUT

2

LT1249

ELECTRICAL CHARACTERISTICS

range, otherwise specifications are at T
VA

= 5V, no load on any outputs, unless otherwise noted.

OUT

= 25°C. Maximum operating voltage (V

A

The ● denotes specifications which apply over the operating temperature

) = 25V, VCC = 18V, I

MAX

= 100µA, CA

AC

OUT

= 3.5V,

PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference

Reference Output Voltage TA = 25°C, Measured at V

Pin 7.39 7.5 7.6 V

SENSE

Reference Output Voltage Worst Case All Line, Temperature ● 7.32 7.5 7.68 V
Reference Output Voltage Line Regulation V

LOCKOUT

< VCC < V

MAX

● –20 5 20 mV

Multiplier

Multiplier Output Current IAC = 100µA, VA

= 5V 35 µA

OUT

Multiplier Output Current Offset RAC = 1M from IAC to GND ● –0.05 –0.5 µA
Multiplier Max Output Current (I
Multiplier Max Output Voltage (I

)I

M(MAX)

• R

M(MAX)

)IAC = 450µA, VA

MOUT

= 450µA, VA

AC

= 7V (Note 2) ● – 375 –250 –150 µA

OUT

= 7V (Note 2) ● –1.25 –1.1 –0.96 V

OUT

Multiplier Gain Constant (Note 3) 0.035 V
IAC Input Resistance IAC from 50µA to 1mA 15 32 50 kΩ

Oscillator

Oscillator Frequency ● 75 100 125 kHz
Control Pin (CA
Synchronization Frequency Range Synchronizing Pulse Low ≤ 0.35V on CA

) Threshold Duty Cycle = 0 ● 1.3 1.8 2.3 V

OUT

OUT

● 127 160 kHz

Gate Driver

Max GTDR Output Voltage 0mA Load, 18V < V
GTDR Output High – 200mA Load, 11.5V ≤ VCC ≤ 15V ● V

CC

< V

(Note 4) ● 12 15 17.5 V

MAX

– 3.0 V

CC

GTDR Output Low (Device Unpowered) VCC = 0V, 50mA Load (Sinking) ● 0.9 1.5 V
GTDR Output Low (Device Active) 200mA Load (Sinking) ● 0.5 1 V
Peak GTDR Current 10nF from GTDR to GND 2 A
GTDR Rise and Fall Time 1nF from GTDR to GND 25 ns
GTDR Max Duty Cycle 90 96 %

–2

Note 1: Absolute Maximum Ratings are those values beyond which the life

Note 3: Multiplier Gain Constant: K =

of a device may be impaired.
Note 2: Current amplifier is in linear mode with 0V input common mode.

W

U

Note 4: Maximum GTDR output voltage is internally clamped for higher

voltages.

V

CC

TYPICAL PERFORMANCE CHARACTERISTICS

Voltage Amplifier Open-Loop
Gain and Phase

100

80

60

40

GAIN (dB)

20

0

–20

10

100

GAIN

PHASE

1k 10k 100k

FREQUENCY (Hz)

1M 10M

1249 G01

0

–20

–40

–60

–80

–100

–120

PHASE (DEG)

400

350

300

250

200

150

100

TRANSCONDUCTANCE (µmho)

50

Transconductance of
Current Amplifier

θ

g

m

0

1k

100k10k

FREQUENCY (Hz)

IAC (VA

1M

I

OUT

M

– 1.5)

1249 G02

10M

2

20

0

–20

–40

–60

–80

–100

–120

–140

PHASE (DEG)

3

LT1249

TEMPERATURE (°C)

–75

FREQUENCY (kHz)

75

1249 G10

–25 25 125

140

130

120

110

100

90

80

70

–50 0 50 100

W

U

TYPICAL PERFORMANCE CHARACTERISTICS

Reference Voltage vs
Temperature

7.536

7.524

7.512

7.500

7.488

7.476

7.464

REFERENCE VOLTAGE (V)

7.452

7.440

7.428
–50 150

–75

–25

JUNCTION TEMPERATURE (°C)

0 25 50 100

75

125

1249 G03

Multiplier Current

300

150

(µA)

M

I

0

0

VA

500

= 5V

OUT

VA

= 4.5V

OUT

VA

= 4V

OUT

VA

= 3.5V

OUT

VA

= 3V

OUT

VA

= 2.5V

OUT

VA

= 2V

OUT

VA

= 6.5V

OUT

VA

= 6V

OUT

VA

= 5.5V

OUT

250

IAC (µA)

1249 G04

SUPPLY CURRENT (mA)

400

300

200

TIME (ns)

100

Supply Current vs Supply Voltage

10

TJ = –55°C

9

TJ = 25°C

8
7

TJ = 125°C

6
5
4
3
2
1
0

1412 16 20 24 28

10

SUPPLY VOLTAGE (V)

22

18

26

GTDR Rise and Fall Time

FALL TIME

RISE TIME

NOTE: GTDR SLEWS

0

0

10

BETWEEN 1V AND 16V

20 30 40

LOAD CAPACITANCE (nF)

1249 G05

1249 G08

GTDR Source Current

18.5
VCC = 18V

18.0

17.5

17.0

16.5

16.0

15.5

15.0

GTDR VOLTAGE (V)

14.5

14.0

13.5

13.0

30

0

TJ = 125°C

TJ = 25°C

TJ = –55°C

–120 –180 –240

–60

SOURCE CURRENT (mA)

–300

1249 G06

GTDR Sink Current

1.1

1.0

0.9

0.8

0.7

0.6

0.5
TA = –55°C

0.4

GTDR VOLTAGE (V)

0.3

0.2

0.1

0

TA = 125°C

0

TA = 25°C

60

120 180 240

SINK CURRENT (mA)

300

1249 G07

Start-Up Supply Current vs
Supply Voltage Switching Frequency

550
500
450
400
350
300
250
200
150

SUPPLY CURRENT (µA)

100

50

50

0

0

4

2610

SUPPLY VOLTAGE (V)

81216

–55°C

25°C

125°C

14 18

20

1249 G09

4