|
|
PDF SC480 Data sheet ( Hoja de datos )
| Número de pieza | SC480 | |
| Descripción | Complete DDR1/2/3 Memory Power Supply | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de SC480 (archivo pdf) en la parte inferior de esta página. Total 25 Páginas | ||
|
No Preview Available !
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. It is a pseudo-fixed frequency constant on-
time controller designed for high efficiency, 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
www.DatasSihneket4aU3.cAompeak 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 efficiency. 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 flag.
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.
Typical Application Circuit
SC480
Complete DDR1/2/3
Memory Power Supply
Features
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 RDS(ON)
Sensing or External RSENSE in Series with Low-Side
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
Applications
¡ Notebook Computers
¡ CPU I/O Supplies
¡ Handheld Terminals and PDAs
¡ LCD Monitors
¡ Network Power Supplies
VTT
VBAT
VDDQ
C4
10uF
C5
10uF
R1
1Meg
VTTSNS
C7
1nF
REF
R6
10R
C9
1uF
5V
C1
1uF
C10
1uF
D1
1 PGND2
2 VTTS
3 VSSA
4 TON
5 REF
6 VCCA
U1
SC480
VDDQ
C8
0.1uF
C2
0.1uF
VBAT
C3
2x10uF
Q1
Q2
PGND1 18
PGND1
ILIM
17
16
RILIM
15
VDDP
VDDP 14
PGD 13
PAD PAD
R4
VDDQ
L1
C6
+
PGOOD
R7 10R
EN/PSV
VTT_EN
5V
C11
1uF
November 3, 2006
1
www.semtech.com
1 page  
SC480
POWER MANAGEMENT
Electrical Characteristics (Cont.)
TEST CONDITIONS: VIN = 15V, VCCA = VDDP = VTTEN = EN/PSV = 5V, VDDQ = VTTIN = 1.8V, RTON = 1MΩ. TAMB = -40 TO +85C.
Parameter
Conditions
25°C
-40°C to 85°C
Units
Min Typ Max Min Max
FB Input Thresholds
FB Logic Input Low
FB Logic Input High
www.DataSGheaette4UD.rciovmes
Shoot-Thru Protection Delay(4)(7)
DL Pull-Down Resistance
DL Sink Current
DL Pull-Up Resistance
DL Source Current
DH Pull-Down Resistance
DH Pull-Up Resistance(8)
DH Sink/Source Current
VTT Pull-Up Resistance
VDDQ Set for 2.5V (DDR1)
VDDQ Set for 1.8V (DDR2)
DH or DL Rising
DL Low
VDL = 2.5V
DL High
VDL = 2.5V
DH Low, BST - LX = 5V
DH High, BST - LX = 5V
VDH = 2.5V
VTTS < REF
0.3
VCCA
- 0.7
30
0.8
3.1
2
1.3
2
2
1.3
0.25
V
V
ns
Ω
A
Ω
A
Ω
Ω
A
Ω
VTT Pull-Down Resistance
VTTS > REF
0.25
Ω
VTT Peak Sink/Source Current(9)
3.6 2.0
A
Notes:
1) The VDDQ DC regulation level is higher than the FB error comparator threshold by 50% of the ripple voltage.
2) Using a current sense resistor, this measurement relates to PGND1 minus the source of the low-side MOSFET.
3) clks = switching cycles, consisting of one high side and one low side gate pulse.
4) Guaranteed by design.
5) Thermal shutdown latches both outputs (VTT and VDDQ) off, requiring VCCA or EN/PSV cycling to reset.
6) VTT soft-start ramp rate is limited to 5.5mV/μs typical. If the VDDQ/2 ramp rate is slower than 5.5mV/μsec, the VTT soft-start ramp will follow the VDDQ/2
ramp.
7) See Shoot-Through Delay Timing Diagram on Page 6.
8) Semtech’s SmartDriver™ FET drive first pulls DH high with a pull-up resistance of 10Ω (typ.) until LX = 1.5V (typ.). At this point, an additional pull-up device is
activated, reducing the resistance to 2Ω (typical). This creates a softer turn-on with minimal power loss, eliminating the need for an external gate or boost
resistor.
9) Provided operation below TJ(MAX) is maintained. VTT output current is also limited by internal MOSFET resistance which is typically 0.25Ω at 25°C and which
increases with temperature, and by available source voltage (typically VDDQ/2).
© 2006 Semtech Corp.
5
www.semtech.com
5 Page 
SC480
POWER MANAGEMENT
Application Information
Referencing Figure 2, the equation for setting the output
voltage is:
+5V +VIN
V OUT (1 R 2 ) x 1.5
R3
Current Limit Circuit
Current limiting of the SC480 can be accomplished in two
www.DatawShaeyest4. UT.choemon-state resistance of the low-side MOSFETs
can be used as the current sensing element, or a sense
resistor in the low-side source can be used if greater ac-
curacy is desired. RDSON sensing is more efficient and
less expensive. In both cases, the RILIM resistor between
the ILIM pin and LX sets the over-current threshold. This
resistor RILIM is connected to a 10μA current source within
the SC480 which is turned on when the low-side MOSFET
turns on. When the voltage drop across the sense resistor
or low-side MOSFET equals the voltage across the RILIMresis-
tor, current limit will activate. The high-side MOSFET will
not be allowed to turn on until the voltage drop across the
sense element (resistor or MOSFET) falls below the voltage
across the RILIM resistor.
The current sensing circuit actually regulates the inductor
valley current, see Figure 3. This means that if the current
limit is set to 10A, the peak current through the inductor
would be 10A plus the peak ripple current, and the average
current through the inductor would be 10A plus 1/2 the
peak-to-peak ripple current.
I PEAK
BST
DH
LX
ILIM
VDDP
DL
PGND
SC480
D1
C2
R1
+
C1
Q1
L1
D2
Q2
+
C3
Vout
Figure 4
T4hweitshchReILmIM a=tiRc1ofaRnDdSRODN SseONnosfinQg2c.ircuit is shown in Figure
Similarly, for resistor sensing, the current through the lower
MOSFET and the source sense resistor develops a voltage
that opposes the voltage developed across RILIM. When the
vdoroltpagaecdroesvselRopILIeMd, aancroovsesr-tchuerRreSnENtSEerxeisstisstoarnrdeathcheehsigvhol-tsaidgee
MOSFET will not be allowed to turn on. The over-current
equation when using an external sense resistor is:
ILOC Valley
10ƫA
x
RILIM
RSENSE
Schematic of resistor sensing circuit is shown in Figure 5
with RILIM = R1 and RSENSE = R4.
+5V +VIN
I LOAD
+
D1 C1
I LIMIT
TIME
Valley Current - Limit Threshold Point
BST
DH
LX
ILIM
VDDP
DL
PGND
SC480
Q1
C2
L1
D2
Q2
R1 R4
+
C3
Vout
Figure 3
Figure 5
© 2006 Semtech Corp.
11
www.semtech.com
11 Page | ||
| Páginas | Total 25 Páginas | |
| PDF Descargar | [ Datasheet SC480.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| SC480 | Complete DDR1/2/3 Memory Power Supply | Semtech Corporation |
| SC4806 | Multiple Function Double Ended PWM Controller | Semtech Corporation |
| SC4808A | High Performance Dual Ended PWM Controller | Semtech Corporation |
| SC4808B | High Performance Dual Ended PWM Controller | Semtech Corporation |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |