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Semtech Corporation - Complete DDR1/2/3 Memory Power Supply

Numéro de référence SC486
Description Complete DDR1/2/3 Memory Power Supply
Fabricant Semtech Corporation 
Logo Semtech Corporation 





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SC486 fiche technique
POWER MANAGEMENT
Description
The SC486 is a combination switching regulator and linear
source/sink regulator intended for DDR1/2/3 memory
systems. The switching regulator is used 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 linear source/sink regulator
is used to generate the memory termination voltage, VTT,
with the ability to source and sink a 3A peak current.
www.DataFSoherett4hUe.coVmDDQ 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.
For the VTT regulator, the output voltage tracks VREF,
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. Additional features include
cycle-by-cycle current limiting, digital soft-start, power
good (all VDDQ only) and over-voltage and under-voltage
protection (VDDQ and VTT). All 3 outputs (VDDQ, VTT and
REF) are actively discharged when VDDQ is disabled,
reducing external component count and cost. The SC486
is available in a 24 pin MLPQ 4mmx4mm Lead-free
package.
Typical Application Circuit
SC486
Complete DDR1/2/3
Memory Power Supply
Features
‹ DDR1, DDR2 and DDR3 compatible
‹ Constant on-time controller for fast dynamic
response on VDDQ
‹ Programmable VDDQ range - 1.5V to 3V
‹ 1% Internal Reference (2% System Accuracy)
‹ Resistor programmable on time for VDDQ
‹ VCCA/VDDP range = 4.5V to 5.5V
‹ VBAT 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
‹ Combined EN and PSAVE pin for VDDQ
‹ Over-voltage/under-voltage fault protection for
both outputs and PGD output (VDDQ only)
‹ 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 and REF are actively discharged in
S4/S5
‹ 24-pin MLPQ (4 x 4mm) Lead-free package, fully
WEEE and RoHS compliant
Applications
‹ Notebook computers
‹ CPU I/O supplies
‹ Handheld terminals and PDAs
‹ LCD monitors
‹ Network power supplies
VBAT 5VSUS 5VRUN
VDDQ
R4 10R
C1
no-pop
R5
C2
1uF
REF
R6
10R
R9
C6
1uF
VTT
VDDQ
R7 10R
C3
no-pop
R8 0R
C7
no-pop
C11
20uF
R1 R2
10R
C8 C9
1nF 1uF
C12
1uF
U1
11 VTTEN
3 VDDQS
2 TON
6 FB
8 REF
9 COMP
10 VTTS
5 VCCA
4 VSSA
14
15
VTT
VTT
12
13
VTTIN
VTTIN
16
17
PGND2
PGND2
5VSUS
SC486
PGD 7
EN/PSV 1
BST 24
DH
ILIM
LX
23
21
22
R10
DL
VDDP
19
20
PGND1 18
C13
1uF
R3 470k
VBAT
D1
C4
0.1uF
4
3
8
56
C5
10uF
L1
7
2
Q1
1
PGOOD
VDDQ
+ C10
Revision: September 13, 2006
1
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