Datasheet LT1950 (Analog Devices) - 8
| Fabricante | Analog Devices |
| Descripción | Single Switch PWM Controller with Auxiliary Boost Converter |
| Páginas / Página | 20 / 8 — BLOCK DIAGRA. Figure 1. LT1950 Block Diagram. OPERATIO |
| Formato / tamaño de archivo | PDF / 223 Kb |
| Idioma del documento | Inglés |
BLOCK DIAGRA. Figure 1. LT1950 Block Diagram. OPERATIO
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LT1950
W BLOCK DIAGRA
V V IN REF VSEC BOOST VIN2 15 6 16 14 11 VIN2 VREF = INTERNAL + SWITCHING PREREGULATOR + EXTERNAL SUPPLY FIXED OFF TIME 11V DISABLE 2.5V (125mA CURRENT LIMIT) – (SOURCE 2.5mA EXTERNALLY) PGND (V + IN) (2.6V) (VIN2) (8V) U/V LOCKOUT U/V LOCKOUT 8V 1.23V – (105/VSEC)% – + – MAX DC ENABLE + CLAMP 1.32V 3µA – (TYPICAL 200kHz) SHDN 7 OSC S ±1A Q 12 GATE DRIVER + SYNC 4 (100-500)khz SLOPE COMP R RAMP 13 PGND ROSC 3 SLOPE 5 13V BLANKING ERROR AMPLIFIER 1.23V + VOLTAGE GAIN = 85dB CURRENT BLANKING – SENSE OVERRIDE CMP CMP – + – + 0mV – >100mV 10 ISENSE 125mV 2 1 8 9 1950 BD FB COMP GND BLANK
Figure 1. LT1950 Block Diagram U OPERATIO
The LT1950 is a constant frequency, current mode con- 11V supply at VIN2 using a small surface mount external troller for DC/DC forward, boost, flyback and SEPIC con- inductor, diode and capacitor. Since VIN2 supplies the verter applications. The Block Diagram in Figure 1 shows output driver of the IC, this architecture achieves high all of the key functions of the IC. GATE drive for an external N-channel power MOSFET even In normal operation, a V though VIN voltage is very low. High GATE drive capability IN voltage as low as 3V allows an internal switcher at the BOOST pin to generate a separate reduces MOSFET RDS(ON) for improved efficiency, 1950fa 8
W BLOCK DIAGRA
V V IN REF VSEC BOOST VIN2 15 6 16 14 11 VIN2 VREF = INTERNAL + SWITCHING PREREGULATOR + EXTERNAL SUPPLY FIXED OFF TIME 11V DISABLE 2.5V (125mA CURRENT LIMIT) – (SOURCE 2.5mA EXTERNALLY) PGND (V + IN) (2.6V) (VIN2) (8V) U/V LOCKOUT U/V LOCKOUT 8V 1.23V – (105/VSEC)% – + – MAX DC ENABLE + CLAMP 1.32V 3µA – (TYPICAL 200kHz) SHDN 7 OSC S ±1A Q 12 GATE DRIVER + SYNC 4 (100-500)khz SLOPE COMP R RAMP 13 PGND ROSC 3 SLOPE 5 13V BLANKING ERROR AMPLIFIER 1.23V + VOLTAGE GAIN = 85dB CURRENT BLANKING – SENSE OVERRIDE CMP CMP – + – + 0mV – >100mV 10 ISENSE 125mV 2 1 8 9 1950 BD FB COMP GND BLANK
Figure 1. LT1950 Block Diagram U OPERATIO
The LT1950 is a constant frequency, current mode con- 11V supply at VIN2 using a small surface mount external troller for DC/DC forward, boost, flyback and SEPIC con- inductor, diode and capacitor. Since VIN2 supplies the verter applications. The Block Diagram in Figure 1 shows output driver of the IC, this architecture achieves high all of the key functions of the IC. GATE drive for an external N-channel power MOSFET even In normal operation, a V though VIN voltage is very low. High GATE drive capability IN voltage as low as 3V allows an internal switcher at the BOOST pin to generate a separate reduces MOSFET RDS(ON) for improved efficiency, 1950fa 8