Datasheet LT1249 (Linear Technology) - 5

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