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SC2596 Datasheet(PDF) 9 Page - Semtech Corporation |
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SC2596 Datasheet(HTML) 9 Page - Semtech Corporation |
9 / 14 page 9 © 2009 Semtech Corp. www.semtech.com POWER MANAGEMENT SC2596 Overview Double Data Rate (DDR) SDRAM was defined by JEDEC 1997. Its clock speed is the same as previous SDRAM but data transfer speed is twice than previous SDRAM. By now, the requirement voltage range is changed from 3.3V to 2.5V or 1.8V; the power dissipation is smaller than SDRAM. For above reasons, it is very popular and widely used in M/B, N/B, Video-cards, CD ROM drives, Disk drives. Regarding the DDR power management solution, there are two topologies can be selected for system design- ers. One is switching mode regulator that has bigger sink/ source current capability, but the cost is higher and needs more board space. Another solution is linear mode regu- lator, which costs less, and needs less board space. For two DIMM motherboards, system designers usually choose the linear mode regulator for DDR power man- agement solution. Application Information Thermal shutdown The SC2596 has built-in thermal detected circuit to pre- vent this device from over temperature and damage. The SC2596 goes into shunt down mode when tem- perature is higher than 165OC. The protection condition will release when the temperature of device drop down by 10OC. AVCC and PVCC AVCC and PVCC are the input supply pins for the SC2596. AVCC is supply voltage for all the internal control circuitry. The AVCC voltage has to be greater than its UVLO thresh- old voltage (2.1V typical) to allow the SC2596 to be nor- mal operation. The PVCC pin provides the rail voltage from where the VTT pin draws load current. There is a limitation between AVCC and PVCC. The PVCC voltage must be less or equal to AVCC voltage to ensure the correct VTT output voltage regulation. VSENSE VSENSE pin is a feedback pin from VTT plane. VTT plane is always a narrow and long strip plane in most montherboard applications. This long strip plane will cause a large trace inductance and trace resistance. Consider the load transient condition, a fast load cur- rent going through VTT strip plane will create a voltage spike on VTT plane and a DC voltage drop for load cur- rent. It is recommanded the VSENSE pin should be con- nected center of VTT plane to improve regulation and transient response. A longer trace of VSENSE may pick up noise and cause the error of load regulation. Hence designer should avoid a longer trace between VSENSE to VTT plane. A 100nF ceramic capacitor close to VSENSE pin is required. VREF VREF pin is an output pin to provid internal reference voltage. System designer can use the voltage for Northbridge chipset and memory. It is necessary to add a ceramic capacitor (100nF) from VREF pin to ground with shortest trace. Typical Application Circuits & Waveforms Four different application circuits are shown below in Fig- ure 1, Figure 2, Figure 3 and Figure 4. Each circuit is designed for a specific condition. See Note a. and b. below for recommended power up sequencing. Application_1: Standard SSTL-2 Application The AVCC pin, PVCC pin and the V DDQ pin can be tied together for SSTL-2 application (Figure 1). It only needs a 2.5V power rail for normal operation. System designer can save the PCB space and reduce the cost. Figure 1: Standard SSTL-2 application. VREF/1.25V 0 VDDQ/EN=2.5V VTT/1.25V SC2596 SC2596 GND 1 EN 2 VSENSE 3 VREF 4 VDDQ 5 AVCC 6 PVCC 7 VTT 8 CIN1 1uF CIN1 1uF Csense 100nF Csense 100nF CIN2 100uF CIN2 100uF COUT 220uF COUT 220uF CREF 100nF CREF 100nF |
Similar Part No. - SC2596_09 |
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Similar Description - SC2596_09 |
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