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Final Electrical Specifications
LT1508 Power Factor and PWM Controller (Voltage Mode)
October 1995
FEATURES
s s s s s s s s s s s s
DESCRIPTION
The LT (R) 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 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.
PFC and PWM Single Chip Solution Synchronized Operation up to 300kHz 99% Power Factor over 20:1 Load Current Range Voltage Mode PWM Instantaneous Overvoltage Protection Dedicated Overvoltage Protection (OVP Pin) Minimal Line Current Dead Zone Typical 250A Start-Up Supply Current Line Switching Noise Filter Low Quiescent Current: 13mA Fast 1.5A Peak Current Gate Drivers Separate Soft-Start Control
APPLICATIONS
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Universal Power Factor Corrected Power Supplies and Preregulators
BLOCK DIAGRAM
VCC 16V TO 10V
VAOUT 10
VREF 7.5V VREF RUN 12
MOUT ISENSE 8 7
CAOUT 6
+ -
2.2V
7A
+
M1
VSENSE 14 7.5V
- -
EA
-
IM CA
IA 25k IB IA2IB IM = 200A2
- +
RUN
+
IAC 9
+
+
0.7V R 2R
7.9V OVP 11 SS1 16 14A
+ -
-
OSC 16V GND2 2
+
1V
-
CL
4 CSET
RSET 15 55% DELAY R
-
14A SS2 13 PWMOK
-
7V TO 4.7V
+ + -
+
NOTE: PWM PULSE IS DELAYED BY 55% DUTY CYCLE AFTER PFC PULSE
19 ILIM
VC 18
50A
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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W
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GND1 3
PKLIM VCC 5 17
- +
R R S Q GTDR1 1
R S
Q
GTDR2 20
200ns BLANKING
16V
1508 BD
1
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 ................................................ 5J 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 Commercial ........................................... 0C to 100C Industrial .......................................... - 40C to 125C Thermal Resistance (Junction-to-Ambient) N Package ................................................... 100C/W SW Package ................................................ 120C/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 N PACKAGE 20-LEAD PDIP 20 GTDR2 19 ILIM 18 VC 17 VCC 16 SS1 15 RSET 14 VSENSE 13 SS2 12 VREF 11 OVP SW PACKAGE 20-LEAD PLASTIC SO WIDE
ORDER PART NUMBER LT1508CN LT1508CS LT1508IN LT1508IS
TJMAX = 125C, JA = 100C/ W (N) TJMAX = 125C, JA = 120C/ W (SW)
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
Maximum operating voltage (VMAX) = 25V, VCC = 18V, RSET = 15k to GND, CSET = 1nF to GND, IAC = 100A, 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
q q q q
MIN
TYP 0.25 13 16.5 10.5
MAX 0.45 19 17.5 11.5 10 - 250
UNITS mA mA V V mV nA dB MHz V V mA
15.5 9.5 - 10 70
VAOUT = 3.5V VSENSE = 0V to 7V
q q
q q
11.3 3
VAOUT = 0V
q
- 25 100 3 13.3 1.1 8
2 17
2
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U
U
WW
U
W
LT1508
ELECTRICAL CHARACTERISTICS
Maximum operating voltage (VMAX) = 25V, VCC = 18V, RSET = 15k to GND, CSET = 1nF to GND, IAC = 100A, ISENSE = 0V, CAOUT = 3.5V, VAOUT = 5V, OVP = VREF. No load on any outputs unless otherwise noted.
PARAMETER Current Amplifier (PFC Section) Current Amp Offset Voltage ISENSE Bias Current Current Amp Voltage Gain Current Amp Unity-Gain Bandwidth Current Amp Output High Current Amp Output Low Current Amp Short-Circuit Current Input Range, ISENSE, MOUT (Linear Operation) Reference Reference Output Voltage VREF Load Regulation VREF Line Regulation VREF Short-Circuit Current VREF Worst Case Current Limit PKLIM Offset Voltage PKLIM Input Current PKLIM to GTDR Propagation Delay Multiplier Multiplier Output Current Multiplier Output Current Offset Multiplier Maximum Output Current Multiplier Gain Constant (Note 1) IAC Input Resistance Oscillator Oscillator Frequency CSET Ramp Peak-to-Peak Amplitude CSET Ramp Valley Voltage Overvoltage Comparator (PFC Section) Comparator Trip Voltage Ratio (VTRIP / VREF) Hysteresis OVP Bias Current OVP Propagation Delay Gate Drivers (GTDR1 and GTDR2) Max Output Voltage Output High Output Low (Device Unpowered) Output Low (Device Active) Peak Output Current Rise and Fall Time Max Duty Cycle (PFC) Max Duty Cycle (PWM) (Note 2) CONDITIONS
q q
MIN
TYP 1 - 25 110 3 8.5 1.1 8
MAX 4 - 250
UNITS mV nA dB MHz V V mA V V mV mV mA V mV A ns A A A V -2 k kHz kHz V V
80
q q
7.2 3 - 0.3 7.39
CAOUT = 0V
q q
2 17 1 7.60 20 50 7.68 25 - 100
IREF = 0mA, TA = 25C - 5mA < IREF < 0mA 11.5V < VCC < VMAX VREF = 0V Load, Line, Temperature
q q q q
- 20 12 7.32 - 25
7.50 5 5 28 7.5
PKLIM = - 0.1V PKLIM Falling from 50mV to - 50mV IAC = 100A, RSET = 15k RAC = 1M from IAC to GND IAC = 450A, RSET = 15k, VAOUT = 7V, MOUT = 0V IAC from 50A to 1mA RSET = 15k, CSET = 1000pF RSET = 15k, CSET = 1500pF
q
- 50 400 35 - 0.05 - 260 0.035 25 100 68 4.7 1.3 1.05 0.35 0.2 100 15 0.9 0.5 0.2 2 25 96
q q
- 286 15
- 0.5 - 235 35 115 78 5.0 1.55 1.06 1
q q
85 58 4.35 1.15 1.04
q
OVP = 7.5V
q
V A ns V V V V V A ns % %
0mA Load, 18V < VCC - 200mA Load, 11.5V VCC 15V VCC = 0V, 50mA Load (Sinking) 200mA Load (Sinking) 10mA Load 10nF from GTDR to GND 1nF from GTDR to GND
q q q q q
12 VCC - 3.0
17.5 1.5 1 0.4
90 44
50
3
LT1508
ELECTRICAL CHARACTERISTICS
VCC = 18V, RSET = 15k to GND, CSET = 1nF to GND, IAC = 100A, ISENSE = 0V, CAOUT = 3.5V, VAOUT = 5V, OVP = VREF. No load on any outputs, unless otherwise noted.
PARAMETER Soft-Start Current SS1 Current (PFC) SS2 Current (PWM) Comparators in PWM Section ILIM Input Current Current Limit Comparator (CL) Threshold GTDR2 Switching Off Threshold at VC or at SS2 VC Input Current PWMOK Comparator Low Threshold (in Terms of VREF) VC Pin High Voltage GTDR2 Turn-On Blanking Time CONDITIONS SS1 = 2.5V SS2 = 1V ILIM = 0V, VC = 1.6V VC > 2.6V RAMP = 0V VC = 0V 1mA into VC Pin
q q q q q q q q
MIN 5 5
TYP 12 12 - 0.3 1.1
MAX 30 30 -2 1.20 - 80 0.70 7.5
UNITS A A A V V A V ns
0.95 1 - 20 0.57 6.2
0.63 6.9 180
The q denotes specifications which apply over the full operating temperature range. IM Note 1: Multiplier Gain Constant: K = IAC (VAOUT - 2)2
Note 2: GTDR2 (PWM) pulse is delayed by 55% duty cycle after GTDR1 (PFC) is set.
TYPICAL PERFORMANCE CHARACTERISTICS
PFC Voltage Amplifier Open-Loop Gain and Phase
100 80 GAIN 60
GAIN (dB)
GAIN (dB)
40 20 0 -20
PHASE
10
100
1k 10k 100k FREQUENCY (Hz)
4
UW
PFC Current Amplifier Open-Loop Gain and Phase
0 -20 -40 -60 -80 -100 100 80 GAIN 60 40 20 0 -20 -40 -60 -80 -100 -120 10M
PHASE (DEG) PHASE (DEG)
0 -20
PHASE
1M
-120 10M
10
100
1k 10k 100k FREQUENCY (Hz)
1M
LT1508 * TPC01
LT1508 * TPC02
LT1508 TYPICAL PERFORMANCE CHARACTERISTICS
Reference Voltage vs Temperature
7.536 7.524
REFERENCE VOLTAGE (V)
300 VAOUT = 7V VAOUT = 6.5V VAOUT = 6V VAOUT = 5V VAOUT = 4.5V VAOUT = 4V VAOUT = 3.5V 0 VAOUT = 3V VAOUT = 2.5V 500
LT1508 * TPC04
7.512 7.500 7.488 7.476 7.464 7.452 7.440 7.428 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (C)
LT1508 * TPC03
IM (A)
Supply Current vs Supply Voltage
16 15 14 TJ = -55C
400
SUPPLY CURRENT (mA)
13
SUPPLY CURRENT (A)
TIME (ns)
12 11 10 9 8 7 6 5
TJ = 125C
TJ = 25C
10
21 SUPPLY VOLTAGE (V)
Frequency vs RSET and CSET
500 450 400 RSET = 10k RSET = 15k RSET = 20k RSET = 30k 1.00 0.99 0.98
MAXIMUM DUTY CYCLE
FREQUENCY (kHz)
350 300 250 200 150 100 50 0 200 600
0.97 0.96 0.95 0.94 0.93 0.92 0.91 RSET = 10k RSET = 15k RSET = 20k RSET = 30k 600 1800 1400 CSET CAPACITANCE (pF) 1000 2200
MOUT CURRENT (mA)
1800 1400 CSET CAPACITANCE (pF)
1000
UW
32
LT1508 * TPC05 LT1508 * TPC08
Multiplier Current
VAOUT = 5.5V
150
0
250 IAC (A)
GTDR Rise and Fall Time
550 500 450
300
Start-Up Supply Current vs Supply Voltage
400 350 300 250 200 150 100 50 0 -55C 25C 125C
FALL TIME 200 RISE TIME 100 NOTE: GTDR SLEWS BETWEEN 1V AND 16V 0 0 10 20 30 40 LOAD CAPACITANCE (nF) 50
0
2
4
6 8 10 12 14 16 18 20 SUPPLY VOLTAGE (V)
LT1508 * TPC07
LT1508 * TPC06
GTDR1 Maximum Duty Cycle vs RSET and CSET
1.5 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 -3.5 -4.0
MOUT Pin Characteristics
TJ = 125C TJ = 25C TJ = -55C
2200
0.90 200
-2.4
-1.2 1.2 0 MOUT VOLTAGE (V)
2.4
LT1508 * TPC10
LT1508 * TPC09
5
LT1508 TYPICAL PERFORMANCE CHARACTERISTICS
RSET Voltage vs Current
120 100 80 60 40 20 0 -20 -40 -60 -80 -100 0 -0.2 -0.4 -0.8 -0.6 RSET CURRENT (mA) -1.0 TJ = 125C TJ = 25C TJ = -55C
PKLIM CURRENT (A)
-360 -300 -240 -180 -120 - 60 0 60 120 180 240 300 -0.8 -0.4 0.4 0 PKLIM VOLTAGE (V) 0.8
LT1508 * TPC12
VRSET - VREF (mV)
PIN FUNCTIONS
PFC SECTION
(For application help with the PFC portion of this chip, see the LT1248 data sheet)
GTDR1 (Pin 1): The PFC MOSFET gate driver is a 1.5A fast totem pole output which is clamped at 15V. Capacitive loads like the MOSFET gates may cause overshoot. A gate series resistor of at least 5 will prevent the overshoot. GND2 (Pin 2): Power Ground. High current spikes occur in this line when either GTDR1 or GTDR2 switches low. GND1 (Pin 3): Analog Ground. CSET (Pin 4): The capacitor from this pin to GND and RSET determines oscillator frequency. The oscillator ramp is 5V and the frequency = 1.5/(RSET CSET). PKLIM (Pin 5): The threshold of the peak current limit comparator is GND. To set current limit, a resistor divider can be connected from VREF to current sense resistor. CAOUT (Pin 6): This is the output of the current amplifier that senses and forces the line current to follow the reference signal that comes from the multiplier by commanding the pulse width modulator. When CAOUT is low, the modulator has zero duty cycle. ISENSE (Pin 7): This is the inverting input of the current amplifier. This pin is clamped at - 0.6V by an ESD protection diode. MOUT (Pin 8): This is the multiplier high impedance current output and the noninverting input of the current amplifier. This pin is clamped at - 0.6V and 3V.
6
UW
PKLIM Pin Characteristics
TJ = 125C TJ = 25C TJ = -55C
LT1508 * TPC11
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IAC (Pin 9): This is the AC line voltage sensing input to the multiplier. It is a current input that is biased at 2V to minimize the crossover dead zone caused by low line voltage. At the pin, a 25k resistor is in series with the current input, so that a lowpass RC can be used to filter out the switching noise coming down from the line with a high line impedance environment. VAOUT (Pin 10): This is the output of the voltage error amplifier. The output is clamped at 13.5V. When the output goes below 2.5V, the multiplier output current is zero. OVP (Pin 11): This is the input to the overvoltage comparator. The threshold is 1.05 times the reference voltage. When the comparator trips, the multiplier, which is quickly inhibited, blanks PFC switching to prevent further overshoot. This pin is also the input to the PWMOK comparator that releases the PWM soft start (SS2) after the PFC output gets close to the final voltage and has a hysteresis of approximately 150V for 382V PFC output. VREF (Pin 12): This is the 7.5V reference. When VCC goes low, VREF will stay at 0V. VREF biases most of the internal circuitry and can source up to 5mA externally. VSENSE (Pin 14): This is the inverting input to the voltage amplifier.
LT1508
PIN FUNCTIONS
RSET (Pin 15): A resistor from RSET to GND sets the oscillator charging current and the maximum multiplier output current which is used to limit the maximum line current. IM(MAX) = 3.75V/RSET SS1 (Pin 16): Soft Start. SS1 is reset to zero for low VCC. When VCC rises above lockout threshold, SS1 is released to ramp up at a rate set by the internal 12A current source and an external capacitor. During this ramp up, PFC reference voltage is equal to SS1 voltage. After SS1 rises past 7.5V, reference voltage remains at 7.5V. VCC (Pin 17): This is the supply for the chip. The LT1508 has two fast gate drivers required to fast charge high power MOSFET gate capacitances. Good supply bypassing is required consisting of a 0.1F ceramic capacitor in parallel with a low ESR electrolytic capacitor (56F or higher) in close proximity to IC GND.
PACKAGE DESCRIPTION Dimension in inches (millimeters) unless otherwise noted.
N Package 20-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
1.040* (26.416) MAX 20 19 18 17 16 15 14 13 12 11
0.300 - 0.325 (7.620 - 8.255)
0.009 - 0.015 (0.229 - 0.381)
0.015 (0.381) MIN
0.005 (0.127) MIN 0.100 0.010 (2.540 0.254) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
(
+0.025 0.325 -0.015 +0.635 8.255 -0.381
)
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(For application help with the PFC portion of this chip, see the LT1248 data sheet)
PWM SECTION SS2 (Pin 13): PWM Soft Start. The comparator PWMOK monitors the OVP pin and releases the SS2 after the PFC output gets close to the final voltage. VC (Pin 18): PWM voltage mode control voltage. Normally connects to the optocoupler output. A pull-up current of 50A flows out of the pin. ILIM (Pin 19): PWM current sense input with trip point set to 1.1V. GTDR2 (Pin 20): The PWM MOSFET gate driver is a 1.5A fast totem pole output. It is clamped at 15V. Capacitive loads like the MOSFET gates may cause overshoot. A gate series resistor of at least 5 will prevent the overshoot.
0.255 0.015* (6.477 0.381)
1 0.130 0.005 (3.302 0.127)
2
3
4
5
6
7
8
9
10
0.045 - 0.065 (1.143 - 1.651)
0.065 (1.651) TYP 0.125 (3.175) MIN 0.018 0.003 (0.457 0.076)
N20 0695
7
LT1508
PACKAGE DESCRIPTION
0.291 - 0.299** (7.391 - 7.595) 0.010 - 0.029 x 45 (0.254 - 0.737)
0.009 - 0.013 (0.229 - 0.330)
NOTE 1 0.016 - 0.050 (0.406 - 1.270)
NOTE: 1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS.
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
RELATED PARTS
PART NUMBER LT1084 LT1105 LT1241-5 LT1247 LT1248 LT1249 LTC(R)1509 DESCRIPTION 5A Low Dropout Linear Regulator Simplified Off-Line Controller High Frequency Current Mode PWM Controller High Frequency Current Mode PWM Controller Minimal Parts Count Power Factor Controller Power Factor and PWM Controller COMMENTS Good for Post Regulation of Switching Power Supplies Solution for Universal Off-Line Inputs with Output to 100W Operates at Oscillator Frequencies up to 500kHz Operates at Oscillator Frequencies up to 1MHz Simplified PFC Design Complete Solution for Universal Off-Line Switching Power Supplies
Full-Feature Average Current Mode Power Factor Controller Provides All Features in 16-Lead Package
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
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Dimension in inches (millimeters) unless otherwise noted. SW Package 20-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
0.496 - 0.512* (12.598 - 13.005) 20 19 18 17 16 15 14 13 12 11
NOTE 1
0.394 - 0.419 (10.007 - 10.643)
1 0.093 - 0.104 (2.362 - 2.642)
2
3
4
5
6
7
8
9
10 0.037 - 0.045 (0.940 - 1.143)
0 - 8 TYP
0.050 (1.270) TYP 0.014 - 0.019 (0.356 - 0.482) TYP
0.004 - 0.012 (0.102 - 0.305)
S20 (WIDE) 0695
LT/GP 1095 2K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1995

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