SC480 SEMTECH [Semtech Corporation], SC480 Datasheet

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SC480

Manufacturer Part Number
SC480
Description
Complete DDR1/2/3 Memory Power Supply
Manufacturer
SEMTECH [Semtech Corporation]
Datasheet

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The SC480 is a combination switching regulator and
linear source/sink regulator intended for DDR1/2/3
memory systems. The purpose of the switching regulator
is to generate the supply voltage, VDDQ, for the memory
system.
time controller designed for high effi ciency, superior DC
accuracy, and fast transient response. The purpose of the
linear source/sink regulator is to generate the memory
termination voltage, VTT, with the ability to source and
sink a 3A peak current.
For the VDDQ regulator, the switching frequency is constant
until a step in load or line voltage occurs at which time the
pulse density, i.e., frequency, will increase or decrease to
counter the transient change in output or input voltage.
After the transient, the frequency will return to steady-state
operation. At lighter loads, the selectable Power-Save
Mode enables the PWM converter to reduce its switching
frequency and improve effi ciency. The integrated gate
drivers feature adaptive shoot-through protection and
soft-switching. Additional features include cycle-by-cycle
current limiting, digital soft-start, over-voltage and under-
voltage protection and a power good fl ag.
For the VTT regulator, the output voltage tracks REF,
which is ½ VDDQ to provide an accurate termination
voltage. The VTT output is generated from a 1.2V to VDDQ
input by a linear source/sink regulator which is designed
for high DC accuracy, fast transient response, and low
external component count. All three outputs (VDDQ, VTT
and REF) are actively discharged when VDDQ is disabled,
reducing external component count and cost. The SC480
is available in a 24-pin MLPQ (4x4 mm) package.
November 3, 2006
POWER MANAGEMENT
Description
Typical Application Circuit
It is a pseudo-fi xed frequency constant on-
VBAT
VTT
VDDQ
REF
R1
1Meg
1nF
C7
C4
10uF
VTTSNS
VDDQ
VDDQ
R6
10R
1uF
C9
C5
10uF
C10
1uF
C1
1uF
5V
1
2
3
4
5
6
PGND2
VTTS
VSSA
TON
REF
VCCA
D1
0.1uF
C8
SC480
U1
1
Features
Applications
PGND1
PGND1
VTT_EN
VDDP
VDDP
R7
PGD
ILIM
PAD
Constant On-Time Controller for Fast Dynamic
Response on VDDQ
DDR1/DDR2/DDR3 Compatible
VDDQ = Fixed 1.8V or 2.5V, or Adjustable from
1.5V to 3.0V
1% Internal Reference (2% System Accuracy)
Resistor Programmable On-Time for VDDQ
VCCA/VDDP Range = 4.5V to 5.5V
VIN Range = 2.5V to 25V
VDDQ DC Current Sense Using Low-Side R
Sensing or External R
FET
Cycle-by-Cycle Current Limit for VDDQ
Digital Soft-Start for VDDQ
Analog Soft-Start for VTT/REF
Smart Over-Voltage VDDQ Protection Against Source-
Current Loads
Combined EN and PSAVE Pin for VDDQ
Over-Voltage/Under-Voltage Fault Protection
Power Good Output
Separate VCCA and VDDP Supplies
VTT/REF Range = 0.75V – 1.5V
VTT Source/Sink 3A Peak
Internal Resistor Divider for VTT/REF
VTT is High Impedance in S3
VDDQ, VTT, REF Are Actively Discharged in S4/S5
24 Lead MLPQ (4x4 mm) Lead-Free Package
Fully WEEE and RoHS Compliant
Notebook Computers
CPU I/O Supplies
Handheld Terminals and PDAs
LCD Monitors
Network Power Supplies
EN/PSV
C2
10R
0.1uF
18
17
16
15
14
13
PAD
Q2
RILIM
R4
C11
1uF
Q1
L1
C6
5V
C3
2x10uF
Memory Power Supply
PGOOD
+
VBAT
Complete DDR1/2/3
VDDQ
SENSE
in Series with Low-Side
www.semtech.com
SC480
DS(ON)

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SC480 Summary of contents

Page 1

... POWER MANAGEMENT Description The SC480 is a combination switching regulator and linear source/sink regulator intended for DDR1/2/3 memory systems. The purpose of the switching regulator is to generate the supply voltage, VDDQ, for the memory system pseudo-fi xed frequency constant on- time controller designed for high effi ciency, superior DC accuracy, and fast transient response ...

Page 2

... T = -40 TO +85C. AMB 25°C -40°C to 85°C Min Typ Max Min Max 1500 2500 800 1400 5 4.5 5.5 70 150 www.semtech.com SC480 Units °C/W °C °C °C kV Units μA μA V μA μA 5 μA μA ...

Page 3

... SC480 Units kΩ kΩ Ω μ kΩ mV Ω Ω mV μA μ ...

Page 4

... Min Typ Max Min Max 8 440 +16 +12 +20 5 0.1 -10 - 3.70 4.35 -12 -16 -8 +12 +8 +16 50 160 150 170 1.2 0.6 1.2 2.4 2.4 3.1 1.5 1 440 5.5 www.semtech.com SC480 Units clks (3) clks (3) % μ μA % μ μs ° MΩ MΩ μA clks (3) mV/μs ...

Page 5

... Min VDDQ Set for 2.5V (DDR1) VDDQ Set for 1.8V (DDR2 Rising DL Low High Low, BST - High, BST - 2.5V DH VTTS < REF VTTS > REF 5 SC480 = -40 TO +85C. AMB 25°C -40°C to 85°C Units Typ Max Min Max 0.3 VCCA - 0.7 30 0.8 3 ...

Page 6

... POWER MANAGEMENT POWER MANAGEMENT Shoot-Through Delay Timing Diagram LX DL tplhDL © 2006 Semtech Corp tplhDH 6 SC480 www.semtech.com ...

Page 7

... POWER MANAGEMENT Pin Confi guration SC480 MLP24 Pin Out PGND2 1 VTTS 2 VSSA 3 T TON 4 5 REF 6 VCCA Pin Description Pin # Pin Name Pin Function 1 PGND2 Power ground for VTT output. Connect to thermal pad and ground plane. 2 VTTS Sense pin for VTT. Connect to VTT at the load. ...

Page 8

... Notes: 1) EN/PSV = 1 = EN/PSV high or fl oating. 2) Typical discharge resistances: VTT = 0.25Ω. REF = 8Ω. 3) VDDQ is discharged via external series resistance which must be added to SC480 internal discharge resistance to calculate discharge times. This is separate from any external load on VDDQ. FB Confi guration Table The FB pin can be confi gured for fi xed or adjustable output voltage as shown. ...

Page 9

... Semtech Corp. VTTEN OTSD POR/SS DRVH FEDLY DRVL VTTPGD OTSD DSCHG POR/SS 1.5V REF CONTROL PWM -30% SD VSSA Figure 1 9 SC480 VTTIN DRVH NOVLP DRVL +12% -12% HI SHOOT THRU LO SENSE FAULTMON www.semtech.com VTT PGND2 VTTS BST DH LX VDDP DL PGND1 ILIM ...

Page 10

... POWER MANAGEMENT Application Information Application Information +5V Bias Supplies The SC480 requires an external +5V bias supply in addition to the battery. If stand-alone capability is required, the +5V supply can be generated with an external linear regulator. To minimize crosstalk, the controller has seven supply pins: VDDP (2 pins), PGND1 (2 pins), PGND2, VCCA and AGND ...

Page 11

... Current Limit Circuit Current limiting of the SC480 can be accomplished in two ways. The on-state resistance of the low-side MOSFETs can be used as the current sensing element sense resistor in the low-side source can be used if greater ac- curacy is desired. RDSON sensing is more effi cient and less expensive ...

Page 12

... VDDQ. If PSAVE mode is enabled at very light loading, this leak can cause VDDQ to slowly rise and reach the OV threshold, causing a hard shutdown. To prevent this, the SC480 uses Smart OVP to prevent this. When VDDQ exceeds 8% above nominal, DL drives high to turn on the low-side MOSFET, which starts to draw current from VDDQ via the inductor ...

Page 13

... Q2 FBK Figure 6 SC480 ESR Requirements The constant on-time control used in the SC480 regulates the ripple voltage at the output capacitor. This signal consists of a term generated by the output ESR of the capacitor and a term based on the increase in voltage across the capacitor due to charging and discharging during the switching cycle ...

Page 14

... The on-time pulse in the SC480 is calculated to give a pseudo-fi xed frequency. Nevertheless, some frequency variation with line and load can be expected. This variation changes the output ripple voltage ...

Page 15

... ON_VBAT(MAX) = 274kHz and f = 251kHz SW_VBAT(MAX) we can calculate suitable values for ON t ON_VBAT V V (MIN) BAT(MIN) OUT 0.5 t ON_VBAT( (MAX) BAT(MAX) OUT 0 1.02μH and L = 1.30μH, VBAT(MIN) VBAT(MAX) SC480 MIN ) 9 OUT MAX ) The OUT OUT (MIN OUT ...

Page 16

... C with the top feedback resistor, R ripple at VFB is large enough. C than 100pF. The value of C TOP lows, where R is the bottom feedback resistor. Firstly BOT calculating the value of Z required: TOP 16 SC480 RIPPLE_VBA ( T MIN ) RIPPLE_VBA ( T MAX ...

Page 17

... OUT BAT ( MIN ) OUT RMS . Refer to manufacturer’s data sheets and RMS I RIPPLE_VBA ( T MIN I I VALLEY OUT 2 R 1.4 DS (ON) I 1.2 VALLEY 4mΩ, giving R = 5.62kΩ DS(ON) ILIM SC480 I OUT A RMS V BAT _ MIN ) A Ohms www.semtech.com ...

Page 18

... T is the junction temperature temperature the total SC480 device dissipation, The SC480 device dissipation can be determined using VCCA • ICCA + VDDP • IDDP + VTT • |ITT| The fi rst two terms are losses for the analog and gate drive circuits and generally do not present a thermal problem ...

Page 19

... BST is also a noisy node and should be kept as short as possible. 4. Connect PGND1 pins on the chip directly to the VDDP decoupling capacitor and then drop vias directly to theground plane. Locate the current limit resistor at the chip with a kelvin connection to the phase node. 19 SC480 www.semtech.com ...

Page 20

... MBR0530 C4 1uF C8 0.1uF 1 PGND2 2 VTTS U1 3 VSSA SC480 4 TON R3 10R 5 REF 6 VCCA C15 1uF C16 0.1uF Figure 7 - Reference Design 20 SC480 Q1 C2 IRF7811 10uF/25V L1 1210 1.5uH Vishay IHLP-5050 Q2 VDDQ IRF7832 R1 5.62K + + C10* C9* 18 PGND1 220uF/12m 220uF/12m 17 PGND1 *Sanyo 4TPL220MC 16 ILIM 15 5V ...

Page 21

... SC480 1.8V Effi ciency vs. Output Current Continuous Conduction Mode VBAT = 10 VBAT = (A) OUT 2.5V Effi ciency vs. Output Current Continuous Conduction Mode VBAT = 10 VBAT = (A) OUT 1.5V Effi ciency vs. Output Current ...

Page 22

... Load Transient Response 5A, Psave Mode Load Transient Response 0A, Psave Mode Load Transient Response 10A © 2006 Semtech Corp. Load Transient Response 5A, Continuous Conduction Mode Load Transient Response 0A, Continuous Conduction Mode Load Transient Response SC480 www.semtech.com ...

Page 23

... POWER MANAGEMENT Typical Characteristics (Cont.) VTT Load Transient Response, 1A Sink/Source, Psave Mode Startup (PSV), EN/PSV Going High © 2006 Semtech Corp. VTT Load Transient Response, 1A Sink/Source, Continuous Conduction Mode Startup (PSV), EN/PSV Going Low, VDDQ = 5A 23 SC480 www.semtech.com ...

Page 24

... MAX MIN NOM MAX A .031 .035 .040 0.80 0.90 1.00 0.02 A1 .000 .001 .002 0.00 0.05 - (.008 (0.20) 0.25 b .007 .010 .012 0.18 0.30 D .151 .157 .163 3.85 4.00 4.15 D1 .100 .106 .110 2.55 2.70 2.80 E .151 .157 .163 3.85 4.00 4.15 E1 .100 .106 .110 2.55 2.70 2.80 e .020 BSC 0.50 BSC L .011 .016 .020 0.30 0.40 0. aaa .004 0.10 bbb .004 0. www.semtech.com SC480 ...

Page 25

... Phone: (805) 498-2111 Fax: (805) 498-3804 © 2006 Semtech Corp. K DIM Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 www.semtech.com 25 SC480 DIMENSIONS INCHES MILLIMETERS (.155) (3.95) 3.10 .122 .106 2.70 .106 2.70 .021 0.50 .010 0.25 .033 0.85 .189 4.80 www.semtech.com ...

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