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PM6685 Dataheets PDF



Part Number PM6685
Manufacturers ST Microelectronics
Logo ST Microelectronics
Description DUAL STEP-DOWN CONTROLLER
Datasheet PM6685 DatasheetPM6685 Datasheet (PDF)

www.DataSheet4U.com PM6685 DUAL STEP-DOWN CONTROLLER WITH AUXILARY VOLTAGES FOR NOTEBOOK SYSTEM POWER Preliminary Data Features ■ CONSTANT ON TIME TOPOLOGY ALLOWS VERY FAST LOAD TRANSIENTS 6V TO 28V INPUT VOLTAGE RANGE FIXED 5V-3.3V OUTPUT VOLTAGES 5V AND 3.3V ALWAYS VOLTAGES AVAILABLE DELIVER 100mA PEAK CURRENT 1.23V ± 1% REFERENCE VOLTAGE AVAILABLE NO RSENSE CURRENT SENSING USING LOW SIDE MOSFETs’ RDS(on) ACCURATE CURRENT SENSE WITH RSENSE NEGATIVE CURRENT LIMIT SOFT START INTERNALLY FIXED .

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www.DataSheet4U.com PM6685 DUAL STEP-DOWN CONTROLLER WITH AUXILARY VOLTAGES FOR NOTEBOOK SYSTEM POWER Preliminary Data Features ■ CONSTANT ON TIME TOPOLOGY ALLOWS VERY FAST LOAD TRANSIENTS 6V TO 28V INPUT VOLTAGE RANGE FIXED 5V-3.3V OUTPUT VOLTAGES 5V AND 3.3V ALWAYS VOLTAGES AVAILABLE DELIVER 100mA PEAK CURRENT 1.23V ± 1% REFERENCE VOLTAGE AVAILABLE NO RSENSE CURRENT SENSING USING LOW SIDE MOSFETs’ RDS(on) ACCURATE CURRENT SENSE WITH RSENSE NEGATIVE CURRENT LIMIT SOFT START INTERNALLY FIXED AT 2ms SOFT OFF FOR OUTPUT DISCHARGE LATCHED OVP AND UVP SELECTABLE PULSE SKIPPING AT LIGHT LOADS SELECTABLE MINIMUM FREQUECY (25kHz) IN PULSE SKIP MODE 4 mW MAXIMUM QUIESCENT POWER INDIPENDENT POWER GOOD SIGNALs OUTPUT VOLTAGE RIPPLE COMPENSATION VFQFPN-32 5X5 ■ ■ ■ ■ Description PM6685 is a dual step-down controller specifically designed to provide extremely high efficiency conversion, with lossless current sensing technique. The constant on-time architecture assures fast load transient response and the embedded voltage feed-forward provides nearly constant switching frequency operation. An embedded integrator control loop compensates the DC voltage error due to the output ripple. Pulse skipping technique increases efficiency at very light load. Moreover a minimum switching frequency of 25kHz is selectable to avoid audio noise issues. The PM6685 provides a selectable switching frequency, allowing either 200kHz/ 300kHz, 300kHz/400Khz or 400kHz/500kHz operation of the 5V/3.3V switching sections... ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Applications ■ ■ ■ ■ NOTEBOOK COMPUTERS TABLET PC OR SLATES MOBILE SYSTEM POWER SUPPLY 3-4 CELLS Li+ BATTERY POWERED DEVICES Order codes Part number PM6685 September 2005 This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice. Marking PM6685 Package VFQFPN-32 5X5 Packing TAPE & REEL Rev 1 1/16 www.st.com 16 PM6685 Contents 1 2 3 4 5 6 7 Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Electrical ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Block & pin connection diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Functional & block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Package Mechanical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2/16 PM6685 1 Typical application circuit 1 Figure 1. Typical application circuit Circuit 3/16 2 Electrical ratings PM6685 2 Table 1. Electrical ratings Absolute maximum ratings Parameter SGND1 to SGND2 COMPx, FSEL, LDO3_SEL, VREF, SKIP to SGND1, SGND2 Enx, SHDN, PGOD_LDO3, OUTx, PGOODx, V CC to SGND1, SGND2 LDO3 to SGND1, SGND2 LGATEx to PGND HGATEx and BOOTx, to PHASEx PHASEx to PGND CSENSEx, to PGND CSENSEx to BOOTx V5SW, LDO5 to PGND VIN to PGND PGND to SGND1, SGND2 Power dissipation at Tamb = 25°C Value Shorted -0.3 to V CC + 0.3 -0.3 to 6 -0.3 to LDO5 + 0.3 -0.3 to LDO5 + 0.3 -0.3 to 6 -0.6 to 36 -0.6 to 42 -6 to 0.3 -0.3 to 0.6 -0.3 to 36 -0.3 to 0.3 2 V V V V V V V V V W V Unit Symbol Table 2. Symbol RthJA TSTG TJ Thermal data Description Thermal Resistance Junction to ambient (mounted on demoboard) Storage temperature range Junction operating temperature range Value 45 -40 to 150 -10 to 125 Unit °C/W °C °C 4/16 PM6685 3 Block & pin connection diagrams 3 Figure 2. Block & pin connection diagrams Pin connection diagram (top view) 5/16 3 Block & pin connection diagrams PM6685 Table 3. Pin No 1 2 3 Pin description PM6685 SGND COMP3 FSEL Function Signal ground. Reference for internal logic circuitry. DC voltage error compensation pin for the 3.3V switching section. Frequency selection pin. It provides a selectable switching frequency, allowing either 200kHz/300kHz, 300kHz/400kHz or 400kHz/500kz operation of the 5V/ 3.3V switching sections. 3.3V SMPS enable input. The 3.3V section is enabled appling a high logic level (>2.4V) to this pin, while is disabled appling a low logic level (<0.8V). When the section is disabled the High Side gate driver goes low and Low Side gate driver goes high. If both EN3 and EN5 pins are low and SHDN pin is high the device enters in standby mode. Shutdown control input. The device enters its shutdown mode with 9µA of supply current if VSHDN is less than the device off threshold voltage and doesn't restart until VSHDN is greater than the device on threshold voltage. The SHDN pin can be connected to Vbatt through a voltage divider to program an undervoltage lockout. In shutdown mode, the gate drivers of the two switching sections are in high impedance. 4 EN3 5 SHDN 6 Power Good ouput .


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