sc2447tstrt Semtech Corporation, sc2447tstrt Datasheet
sc2447tstrt
Related parts for sc2447tstrt
sc2447tstrt Summary of contents
Page 1
POWER MANAGEMENT Description The SC2447 is a versatile high-frequency dual phase PWM step-down controller optimized for Philips and Renesas DrMOS . Both phases are capable of sourcing or sink- TM ing load currents, making the SC2447 suitable for net- working ...
Page 2
POWER MANAGEMENT Pin Configurations TOP VIEW 1 28 CS1 CS1 ROSC 4 25 IN1 COMP1 6 23 SYNC 7 22 AGND 8 21 REF 9 20 REFOUT 19 REFIN 10 COMP2 11 18 IN2- ...
Page 3
POWER MANAGEMENT Recommended Operating Conditions The performance is not guarantied if exceeding the specifications below ...
Page 4
POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: AVCC = 12V, SYNC = 0, R OSC ...
Page 5
POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: AVCC = 12V, SYNC = 0, R OSC ...
Page 6
POWER MANAGEMENT Typical Performance Characteristics © 2006 Semtech Corp SC2447 www.semtech.com ...
Page 7
POWER MANAGEMENT Typical Application Circuit Performance Circuit Conditions: 2-Output Configuration as in Figure 16. V Soft-Start OUT1 V OUT1 1V/div V SS1/EN1 2V/div I OUT1 10A/div 10ms/div Output Voltage Ripple (V ) OUT1 V OUT1 20mV/div I ...
Page 8
POWER MANAGEMENT Typical Application Circuit Performance Circuit Conditions: 2-Output Configuration as in Figure 16. V Output Voltage Ripple (V ) OUT2 V OUT2 20mV/div I OUT2 10A/div V SW2 10V/div I =25A 2µs/DIV OUT2 Output Voltage Ripple V & V ...
Page 9
POWER MANAGEMENT Typical Application Circuit Performance Circuit Conditions: 2-Phase Configuration as in Figure 17, V Soft-Start Up V OUT 0.5V/div V SS1/EN1 2V/div I OUT 20A/div 10ms/div Output Voltage Ripple (V ) OUT V OUT 20mV/div I OUT 50A/div V ...
Page 10
POWER MANAGEMENT Pin Descriptions ...
Page 11
POWER MANAGEMENT Block Diagram SYNC 6 FREQUENCY CLK DIVIDER OSCILLATOR ROSC 3 SLOPE COMP. COMP1 5 IN1 EA1 REF + 8 REFSS1 SLOPE1 CS1 Σ ISEN1 CS1 ILIM1+ - 50mV ...
Page 12
POWER MANAGEMENT Block Diagram 2.85V - + 9.5uA SS/EN 17.0uA UV Figure 4. Soft-Start and Overload Hiccup Control Circuit 2006 Semtech Corp. S 0.5V/3. 0.8V (0.6V min 46.5uA S 12 SC2447 OL COMP SSL ...
Page 13
POWER MANAGEMENT Timing Chart A VCC 4.5V 1.5V 1.25V 0 0. REF 0 0 GDH in high impedance state (a) Normal Start VCC VCC V V SS/EN SS/ ...
Page 14
POWER MANAGEMENT Timing Chart 3.2V Enable Hiccup 2.85V 1.50V 1.25V 0.8V 0.5V 0V 0.5V 0V GDH i n high impedance state Figure 7. SC2447 Overload Hiccup Operation Timing Diagram 2006 Semtech Corp. Reference Voltage Min.(V ...
Page 15
POWER MANAGEMENT Application Information The SC2447 consists of two current-mode synchronous buck controllers with many integrated functions. The SC2447 can be used to generate: 1) two independent outputs from a common input or two different inputs or, 2) dual-phase output ...
Page 16
POWER MANAGEMENT Application Information (Cont.) Setting the Switching Frequency The switching frequency is set with an external resistor connected from Pin 3 to the ground. The set frequency is inversely proportional to the resistor value (Figure 8). 800 700 600 ...
Page 17
POWER MANAGEMENT Application Information (Cont.) charge balance between the load and the converter output. The third term is voltage ripple due to ESL and the fourth term is the voltage ripple due to ESR. The total output voltage ripple is ...
Page 18
POWER MANAGEMENT Application Information (Cont.) they should be calculated using the following formulae. + ω ω ...
Page 19
POWER MANAGEMENT Application Information (Cont.) For reliable operation, the maximum power dissipation in the capacitors should not result in more than 10 temperature rise. Many manufacturers specify the maximum allowable ripple current (ARMS), rating of the capacitor at a given ...
Page 20
POWER MANAGEMENT Application Information (Cont.) average current mode control), this current sensing method is sufficient without time constant matching requirement. In the current mode control as implemented in SC2447, voltage ripple required for PWM operation ...
Page 21
POWER MANAGEMENT Application Information (Cont.) Overload Protection and Hiccup During start-up, the capacitor from the SS/EN pin to ground functions as a soft-start capacitor. After the converter starts and enters regulation, the same capacitor operates as an overload shutoff timing ...
Page 22
POWER MANAGEMENT Application Information (Cont.) Only the voltages in boldface can be precisely set with standard 1% resistors. From this table, one may also observe that when the value − − ...
Page 23
POWER MANAGEMENT Application Information (Cont.) PC Board Layout Issues Circuit board layout is very important for the proper operation of high frequency switching power converters. A power ground plane is required to reduce ground bounces. The followings are suggested for ...
Page 24
POWER MANAGEMENT Typical Application Schematic 2006 Semtech Corp. 24 SC2447 www.semtech.com ...
Page 25
POWER MANAGEMENT Typical Application Schematic 2006 Semtech Corp. 25 SC2447 www.semtech.com ...
Page 26
... GAGE PLANE 0.25 A SEE DETAIL SIDE VIEW AND - DETERMINED AT DATUM PLANE -H- DIM Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804 26 SC2447 DIMENSIONS INCHES MILLIMETERS NOM MAX MIN NOM MAX - - - .047 1. ...