SC488_DS_2006_Mar_6.indd
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1
POWER MANAGEMENT
SC488
Complete DDR1/2
Memory Power Supply
March 6, 2006
Description
Features
The SC488 is a combination switching regulator and
linear source/sink regulator intended for DDR1/2 memory
systems. The purpose of the switching regulator is to
generate the supply voltage, VDDQ, for the memory system.
It is a pseudo-fi xed frequency constant on-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 2.8A peak
currents.
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 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 SC488 is available
in a 24-pin MLPQ (4x4 mm) package.
Constant on-time controller for fast dynamic
response on VDDQ
DDR1/DDR2/DDR3 compatible
VDDQ = fi xed 1.8V or 2.5V, or adjustable from
1.5V to 3.0V
1.5% internal reference (2.5% 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
DS(ON)
Sensing or external R
SENSE
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 2.8A 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
Notebook computers
CPU I/O supplies
Handheld terminals and PDAs
LCD monitors
Network power supplies
Applications
Typical Application Circuit
REF
R7
10R
C10
1uF
VTT
C8
0.1uF
Q1
Q2
D1
C3
2x10uF
VBAT
R1
1Meg
L1
+
C6
VDDQ
VTT_EN
R6
10R
C9
1uF
VBAT
C7
1nF
C1
1uF
EN/PSV
C4
10uF
PGND2
1
VTTS
2
VSSA
3
TON
4
REF
5
VCCA
6
NC
7
VTTEN
10
FB
9
LX
20
DL
19
PGND1
18
PGND1
17
ILIM
16
VDDP
15
VDDP
14
NC
12
EN/PSV
11
VDDQS
8
PGD
13
VTTIN
23
VTT
24
BST
22
DH
21
PAD
U1
SC480
R4
VDDQ
5V
VTTSNS
PAD
C2
0.1uF
5V
PGOOD
RILIM
C11
1uF
C5
10uF
VDDQ
VDDQ
SC488
2
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
SC488
Electrical Characteristics
Exceeding the specifi cations below may result in permanent damage to the device or device malfunction. Operation outside of the parameters specifi ed in the
Electrical Characteristics section is not implied. Exposure to absolute maximum rated conditions for extended periods of time may affect device reliability.
Test Conditions: V
IN
= 15V, VCCA = VDDP = VTTEN = EN/PSV = 5V, VDDQ = VTTIN = 1.8V, R
TON
= 1M. T
AMB
= -40 to +85C.
Parameter
Symbol
Maximum
Units
TON to VSSA
-0.3 to +25.0
V
DH, BST to PGND1
-0.3 to +31.0
V
BST, DH to LX
-0.3 to +6.0
V
LX to PGND1
-2.0 to +25.0
V
DL, ILIM, VDDP to PGND1
-0.3 to +6.0
V
VDDP to DL
-0.3 to +6.0
V
VTTIN to PGND2; VTT to PGND2; VTTIN to VTT
-0.3 to +6.0
V
EN/PSV, FB, PGD, REF, VCCA, VDDQS, VTTEN, VTTS to VSSA
-0.3 to +6.0
V
VCCA to EN/PSV, FB, REF, VDDQS, VTT, VTTEN, VTTIN, VTTS
-0.3 to +6.0
V
PGND1 to PGND2; PGND1 to VSSA; PGND2 to VSSA
-0.3 to +0.3
V
Thermal Resistance Junction to Ambient
(1)
JA
30.5
C/W
Operating Junction Temperature Range
T
J
-40 to +150
C
Storage Temperature Range
T
STG
-65 to +150
C
Peak IR Refl ow Temperature, 10s - 40s
T
PKG
260
C
ESD Protection Level
(2)
V
ESD
2
kV
Parameter
Conditions
25C
-40C to 85C
Units
Min
Typ
Max
Min
Max
Input Supplies
VCCA Operating Current
S0 State (VTT on);
EN/PSV = VCCA;
FB > Regulation Point, IVDDQ = 0A
1500
2500
A
VCCA Operating Current
S3 State (VTT off);
EN/PSV = VCCA;
FB > Regulation Point, IVDDQ = 0A
800
1400
A
VCCA Operating Voltage
5
4.5
5.5
V
VDDP Operating Current
FB > Regulation Point, IVDDQ = 0A
70
150
A
TON Operating Current
RTON = 1M
15
A
Notes:
1) Calculated from package in still air, mounted to 3" x 4.5", 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards.
2) Tested according to JEDEC standard JESD22-A114-B.
Absolute Maximum Ratings
3
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
SC488
Test Conditions: V
IN
= 15V, VCCA = VDDP = VTTEN = EN/PSV = 5V, VDDQ = VTTIN = 1.8V, R
TON
= 1M. T
AMB
= -40 to +85C.
Parameter
Conditions
25C
-40C to 85C
Units
Min
Typ
Max
Min
Max
Input Supplies (Cont.)
VTTIN Operating Current
IVTT = 0A
1
5
A
VCCA + VDDP + TON
Shutdown Current
EN/PSV = VTTEN = 0V
5
22
A
VTTIN Shutdown Current
EN/PSV = VTTEN = 0V
1
A
VDDQ Controller
FB Error Comparator
Threshold
(1)
With Adjustable Resistor Divider
1.500
1.4775
1.5225
V
VDDQS Regulation
Threshold
FB = AGND
2.5
2.4625
2.5375
V
FB = VCCA
1.8
1.773
1.827
V
On-Time
RTON = 1M, VDDQ = 1.8V
460
368
552
ns
RTON = 500k, VDDQ = 1.8V
265
212
318
Minimum Off-Time
400
550
ns
VDDQS Input Resistance
FB < 0.3V
80
k
FB > 0.3V
91
k
VDDQS Shutdown
Discharge Resistance
EN/PSV = GND
16
FB Leakage Current
-1.0
1.0
A
VDDQ Smart
Psave Threshold
8
%
VTT Controller
REF Source Current
10
mA
REF Sink Resistance
50
k
REF Output Accuracy
IREF = 0 to 10mA
900
882
918
mV
Shutdown Discharge
Resistance
(EN/PSV = GND)
VTT
0.32
REF
8
VTT Output Accuracy
(with respect to REF)
-2A < I
VTT
< 2A
(9)
0
-40
+40
mV
VTTS Leakage Current
-1.0
1.0
A
Electrical Characteristics (Cont.)
4
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
SC488
Test Conditions: V
IN
= 15V, VCCA = VDDP = VTTEN = EN/PSV = 5V, VDDQ = VTTIN = 1.8V, R
TON
= 1M. T
AMB
= -40 to +85C.
Parameter
Conditions
25C
-40C to 85C
Units
Min
Typ
Max
Min
Max
Current Sensing
ILIM Current
DL High
10
9
11
A
Current Comparator
Offset
PGND1 - ILIM
-10
10
mV
Zero-Crossing Threshold
PGND1 - LX, EN/PSV = 5V
5
mV
VDDQ Fault Protection
Current Limit (Positive)
(2)
PGND1 - LX, RLIM = 5k
50
35
65
mV
PGND1 - LX, RLIM = 10k
100
80
120
PGND1 - LX, RLIM = 20k
200
170
230
Current Limit (Negative)
PGND1 - LX
-125
-160
-90
mV
Output Under-Voltage
Fault
With Respect to FB Regulation Point
-30
-35
-25
%
Under-Voltage Fault Delay
FB Forced Below UV V
TH
8
clks
(3)
Under-Voltage Blank Time
From EN High
440
clks
(3)
Output Over-Voltage Fault
With Respect to FB Regulation Point
+16
+12
+20
%
Over-Voltage Fault Delay
FB Above Over-Voltage
Threshold
5
s
PGD Low Output Voltage
Sink 1mA
0.1
V
PGD Leakage Current
FB in Regulation, PGD = 5V
1
A
PGD UV Threshold
With Respect to FB Regulation Point
-10
-12
-8
%
PGD Fault Delay
FB Forced Outside PGD Window
5
s
VCCA Under-Voltage
(UVLO)
Falling Edge (Hysteresis 100 mV)
4
3.70
4.35
V
VTT Fault Protection
UV Lower Threshold
VTT w/rt REF
-12
-16
-8
%
OV Upper Threshold
VTT w/rt REF
+12
+8
+16
%
Fault Shutdown Delay
VTT Outside OV/UV Window
50
s
Thermal Shutdown
(4)(5)
160
150
170
C
Electrical Characteristics (Cont.)
5
2006 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
SC488
Parameter
Conditions
25C
-40C to 85C
Units
Min
Typ
Max
Min
Max
Inputs/Outputs
Logic Input Low Voltage
EN/PSV Low/Low (Disabled)
1.2
V
VTTEN Low (VTT Disabled)
0.6
Logic Input High Voltage
EN/PSV Low/High
(Enabled, Psave Disabled)
1.2
2.4
V
VTTEN High (VTT Enabled)
2.4
Logic Input High Voltage
EN/PSV High/High
(Enabled, Psave Enabled)
3.1
V
EN/PSV Input Resistance
Sourcing
1.5
M
Sinking
1.0
M
VTTEN Leakage Current
-1
+1
A
Soft-Start
VDDQ Soft-Start
Ramp Time
EN/PSV High to PGD High
440
clks
(3)
VTT Soft-Start
Ramp Rate
(6)
5.5
mV/s
FB Input Thresholds
FB Logic Input Low
VDDQ Set for 2.5V (DDR1)
0.3
V
FB Logic Input High
VDDQ Set for 1.8V (DDR2)
VCCA
- 0.7
V
Gate Drives
Shoot-Thru Protection
Delay
(4)(7)
DH or DL Rising
30
ns
DL Pull-Down Resistance
DL Low
0.8
DL Sink Current
V
DL
= 2.5V
3.1
A
DL Pull-Up Resistance
DL High
2
DL Source Current
V
DL
= 2.5V
1.3
A
DH Pull-Down Resistance
DH Low, BST - LX = 5V
2
DH Pull-Up Resistance
(8)
DH High, BST - LX = 5V
2
Test Conditions: V
IN
= 15V, VCCA = VDDP = VTTEN = EN/PSV = 5V, VDDQ = VTTIN = 1.8V, R
TON
= 1M. T
AMB
= -40 to +85C.
Electrical Characteristics (Cont.)
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