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SS6577COTR Fiches technique(PDF) 8 Page - Silicon Standard Corp. |
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SS6577COTR Fiches technique(HTML) 8 Page - Silicon Standard Corp. |
8 / 14 page www.SiliconStandard.com 8 of 14 SS6577 Rev.1.02 3/26/2004 PIN DESCRIPTIONS PIN 1: CS - Current sense comparator invert- ing input, not to exceed VIN volt- age. Built in offsets between the CS and VIN pins in conjunction with RSENSE set the current trip thresholds. PIN 2: ITH/RUN -Combination of error amplifier compensation point and run con- trol inputs. The current compara- tor threshold increases with this control voltage. Forcing this pin below 0.8V causes the device to be shutdown. PIN 3: FB - Feedback error amplifier input, to compare the feedback voltage with the internal reference voltage. Connecting a resistor R2 to con- verter output node and a resistor R1 to ground yields the output voltage: VOUT=0.8 x (R1+R2)/ R1 PIN4: GND - Singal GND for IC. All voltage lev- els are measured with respect to this pin. PIN 5: SW - Switch node connection to induc- tor. In buck converter applications the voltage swing at this pin is from a schottky diode voltage drop below ground to VIN PIN 6: DRI - External high-side N-MOSFET gate drive pin. Connect DRI to gate of the external high-side N- MOSFET. PIN 7: BOOST- Supply to high-side floating driver. The bootstrap capacitor C3 is returned to this pin. PIN 8: VIN - The chip power supply pin. It also provides the gate bias charge for all the MOSFETs controlled by the IC. Recommend supply volt- age is 4.5V~24V. APPLICATION INFORMATION Introduction The SS6 577 is a current mode switching regulator controller that drives an external N-channel power MOSFET with constant frequency architecture. It uses an external divider to adjust output voltage with excellent line regulation and load regulation. A maximum high duty cycle limit of 95% provides low dropout operation, which extends operating time in battery-operated system. Wide input voltage ranges from 4.5V to 24V, and a switching frequency of 500KHz allows smaller sized filter components. The operating current level is user-programmable via an external current sense resistor and it automatically enters PFM operation at low output current to boost circuit efficiency. A multifunction pin (ITH/RUN) allows external com- pensation plus shutdown. A built-in soft start can properly provide sequenced supplies. Available packages are SOP8 and MSOP8 for SMD. Principle of Operation The SS6 577 uses a current mode with a constant fre quency architecture. Normally high-side MOSFET turns on each cycle when oscillator sets RS latch and it turns off when internal current comparator re- sets RS latch. Voltage on ITH/RUN pin, which is the output voltage of voltage error amplifier, will control peak inductor current. The output voltage feeds back to VFB pin so that the error amplifier receives a voltage through external resistor divider. When load current increases, it causes a slight decrease |
Numéro de pièce similaire - SS6577COTR |
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Description similaire - SS6577COTR |
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