LT1247 Linear Technology, LT1247 Datasheet
LT1247
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LT1247 Summary of contents
Page 1
... These devices are de- signed to be improved plug compatible versions of the industry standard UC1842 PWM circuit. The LT1246/ LT1247 are optimized for off-line and DC/DC converter applications. They contain a temperature compensated reference, high gain error amplifier, current sensing com- parator, and a high current totem pole output stage ideally suited to driving power MOSFETs ...
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... Analog Inputs (Pins 2, 3) .............................. – 0 Error Amplifier Output Sink Current ..................... 10mA Power Dissipation ............................... 1W A Operating Junction Temperature Range LT1246C/LT1247C ............................. 100 C Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec)................. 300 C *The 1A rating for output current is based on transient switching requirements. ELECTRICAL C ...
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... PIN 3 = 20mA = 200mA = 20mA = 200mA = 1nF 1nF 1mA = Note 2: Low duty cycle pulse techniques are used during test to maintain junction temperature close to ambient. = 10k 3.3nF LT1246/LT1247 MIN TYP MAX 5 5.6 0.2 1.1 2.85 3.00 3.15 0.90 1.00 1.10 70 –1 – 1.5 0.25 0.4 0.75 2.2 12 ...
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... Oscillator Sink Current 8 PIN 4 8.6 8.5 8.4 8.3 8.2 8.1 8.0 7.9 7.8 7.7 –50 – 100 125 TEMPERATURE ( C) LT1246 • TPC07 HARA TERISTICS C LT1247 Undervoltage Lockout START-UP THRESHOLD 8 MINIMUM OPERATING VOLTAGE 7 6 –50 – 100 TEMPERATURE ( C) 1247 TPC02 Supply Current 15V 10k T ...
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... C 1 OUTPUT SINK CURRENT (mA) LT1246 • TPC14 225 1.2 180 1.0 135 0.8 PHASE 90 0.6 45 0.4 0 0.2 –45 100k 1M 10M LT1246 • TPC16 LT1246/LT1247 High Level Output Saturation Voltage 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 125 0 100 OUTPUT SOURCE CURRENT (mA) Supply Current vs Oscillator Frequency 10k 100k OSCILLATOR FREQUENCY (Hz) ...
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... LT1246/LT1247 W U TYPICAL PERFOR A Output Deadtime vs Oscillator Frequency 100 OSCILLATOR FREQUENCY (kHz) Output Rise and Fall Time V = 15V TIME 50ns/DIV 1nF L 1246/7 G20 COMP (Pin 1): Compensation Pin. This pin is the output of the Error Amplifier and is made available for loop compen- sation ...
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... C is set by the difference between T the current supplied by R and the discharge current of the T LT1246/LT1247. The discharge current of the device is trimmed to 8.2mA. For large values of R will be determined by the discharge current of the device and the value the value ...
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... Blanking A unique feature of the LT1246/LT1247 is the built-in blanking circuit at the output of the current sense com- parator. A common problem with current mode PWM circuits is erratic operation due to noise at the current sense input ...
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... This can cause erratic operation of the device. In these cases a Schottky clamp diode is recommended from output to ground. Reference The internal reference of the LT1246/LT1247 Bandgap reference, trimmed to within 1% initial toler- ance. The reference is used to power the majority of the internal logic and the oscillator circuitry. The oscillator charging current is supplied from the reference ...
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... LT1246/LT1247 TYPICAL PPLICATI EXTERNAL V REF 8 R COMP 1 C FEEDBACK 2 I SENSE 3 V REF COMP R2 100k 1 FEEDBACK – 2.5V 1.67 V CLAMP ( ( External Clock Synchronization V REF 8 5V REF OSCILLATOR C SYNC T 0.01 F INPUT REQUIRED IF THE SYNC AMPLITUDE IS LARGE ENOUGH TO PULL THE BOTTOM OF C MORE THAN 300mV BELOW GROUND ...
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... Slope Compensation at I Pin SENSE REFERENCE ENABLE 5V REF MAIN BIAS REFERENCE PULLDOWN OSCILLATOR 5.6V 1V 1mA 2R – Slope Compensation at Error Amp 5V REF MAIN BIAS OSCILLATOR 5.6V 1V 1mA 2R – LT1246/LT1247 UV LOCKOUT V CC OUTPUT 7 PULLDOWN OUTPUT 18V GND 5 BLANKING + 1.5V – I SENSE 3 LT1246 • TA08 UV LOCKOUT REFERENCE ENABLE ...
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... LT1246/LT1247 PACKAGE DESCRIPTIO 0.300 – 0.325 (7.620 – 8.255) 0.065 (1.651) TYP 0.009 – 0.015 (0.229 – 0.381) +0.025 0.045 0.015 0.325 –0.015 (1.143 0.381) +0.635 8.255 –0.381 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTURSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm). ...