regulation solution up to 4 paralleled PWM channels. The
solution can also be configured as 2, 3, or 4-phase form.
Multi-phase buck regulator utilizes the phase-shift timing
control to allow interleaved switching of the power switches.
This architecture minimizes the core voltage ripple and the
input current ripple, which leads to optimized voltage regu-
lator design for power density, transient responses, and
the thermal performances.
To satisfy the highly dynamic nature of the modern
microprocessors, the SC2643VX adopts peak current mode
control topology which ensures wide control loop
band-
width and fast transient responses. The current mode
control provides intrinsic phase current matching. The maxi-
mum ripple frequency is greater than 2.8MHz.
One of the outstanding features of the SC2643VX is its
voltage regulation accuracy. Not only it provides better
than 0.5% set point accuracy, but also the accuracy to
fully complaint with the stringent load line slope
specifications mandated by the modern microprocessors.
Lossless output current sensing ensures the regulator
output voltage is accurately positioned according to the
load current condition, and an internal temperature
compensation technology further enhances the perfor-
mance of voltage accuracy.
The patented Combi-Sense
TM
topology is employed by
SC2643VX. The MOSFET R
ds(on)
and the output inductor
winding resistance are used to generate the phase current
information. The Combi-Sense
TM
MOSFET driver plus the
SC2643VX enables the complete solution.
The SC2643VX is a multi-platform controller. It conforms
to Intel VRM/VRD10.X, VRM9.X, and AMD K-8 (Opteron
TM
)
VID specifications. With very minor changes of the sche-
matic and the layout, the SC2643VX based solution can
be ported form one platform to another. This greatly ben-
efits the system manufactures for reductions of design
cycle and minimize the inventory management.
Multi-Platform
Multi-Phase PWM Controller
The SC2643VX supports VID-on-Fly applications for any
platform. The cycle-by-cycle current limit plus the intelli-
gent over current shut down provide the maximum versa-
tility of the system without false tripping under all possible
changes of VID and load conditions. The differential volt-
age feedback sense eliminates the error caused by high
load current on the ground plane. External offset is easy
to achieve for any platforms and the VID settings. The
enable function is also provided to interface with the cor-
responding system signal for correct start up timing and
shut down timing.
(Multiple Patents Pending)
SC2643VX
Features
VRD/VRM10.X, VRM9.X, and K-8 compliant
Core Voltage Set Point Accuracy 0.5%
Combi-Sense
TM
Current Mode Control
Intrinsic Phase Current Matching
Fast Transient Responses
Active Droop with Temperature Compensation to
Meet Load Line Slope
Support VID-on-Fly with 5 or 6 bit VID
Enable Function for Power Sequencing
Cycle-by-Cycle Peak Current Limit
Intelligent Over Current Shut Down
Over Voltage Protection When Using Semtech
Combi-Sense
TM
Driver
Under Voltage Protection Built in
External programmable Soft-Start
Externally programmable switching frequency (up to
2.8MHz output voltage ripple frequency)
2, 3, or 4-Phase Configurations
24-Pin SOIC or TSSOP Packages
Applications
Voltage Regulator VRD/VRM10.X
Voltage Regulator VRM9.X
Voltage Regulator K-8
High Current, Low Voltage Step Down DC/DC
Converters
July 27, 2004
1
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SC2643VX
VIN
ATX12V
1
2
R1
D1
C3
1uF
U1
4
3
2
1
PN3
R6
9
PGND
VPN
V IN
VR EG
BG
1
M2
M3
R11
IR0
C10
5
6
7
8
2.2nF
OS4
OUTSEN
OUT4
OUT3
OUT2
OUT1
AGND
OSCREF
PGOOD
VID5
VID0
12
VID2
VID1
19
18
17
16
15
14
VID3
13
R19
100
Rosc
AUX2
1nF
PN2
C19
4
3
2
1
PN2
CO
BST
TG
DRN
R17
20
21
D1N4148
1uF
M4
C15
4.7uF/1206
22
23
VCC
24
C11
1uF
D2
C12
4.7uF
VIN
C13
M1
D1N4148
PN3
R2
R3
R4
C5
1nF
C9
R10
R12
100
U2
1
CO
BST
TG
DRN
C4
R5
C6
R7
C7
R8
C8
R9
AUX3
2R2
AUX1
AUX2
AUX3
VOUT
C2
4.7uF/1206
640nH
ATX12V
L1
1800uF/16V
C1
+
1
L2
2
Note (3)
2
OS2
OS1
BGOUT
ERROUT
GNDSEN
FB
DACSTEP
VCC
VID4
R13
4
1.5K
5
R14
R16
OFFSET-
C17
8
9
10
R20
11
10
C21
4.7uF
C16
1uF
C18
0.1uF
VCC
7
6
VCC
R15
3
VRM_EN
OS3
SC1211
(Open Collector Input, No Pull-up)
1800uF/16V
C14
+
OFFSET+
Note (4)
ATX12V
SC 1211
1
PGND
VPN
V IN
VR EG
BG
9
1
M5
U3
5
6
7
8
M6
R18
IR0
C20
2.2nF
L3
2
VOUT
+
Cout
Note (2)
VID0
VID1
VID2
VID3
VID4
SC2643VX
C22
1uF
D3
D1N4148
V_CORE-
C23
4.7uF
C24
1uF
M7
C26
4.7uF/1206
VIN
PGND
1800uF/16V
C25
+
POWER MANAGEMENT
Typical Application Circuit
Pull-up Voltage
VR10: 2V
VRM9.x: 5V
K-8: 12V
VID5
AUX1
1nF
SC 1211
C27
CO
BST
TG
DRN
V_CORE+
DIFFERENTIAL PAIR
FOR REMOTE SENSE
PN1
4
3
2
1
PN1
R21
9
VPN
V IN
VR EG
BG
1
1
L4
2
Note (2)
R23
100
PGND
R22
M8
U4
5
6
7
8
M9
IR0
C28
2.2nF
C29
PWRGOOD (Open Collector Output)
1uF
C30
4.7uF
Note (1)
R24
0R0
Notes: (1)
(2)
(3)
(4)
Output filter design: Please follow guidelines issued by Intel and AMD.
Please follow guidelines issued by Intel and AMD.
Open collector/drain input, no pull-up.
Use the same power source as FET driver’s (SC1211).
2004 Semtech Corp.
2
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SC2643VX
POWER MANAGEMENT
Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the
Electrical Characteristics section is not implied. Unless otherwise specified, all other voltages are referenced to AGND.
Parameter
Supply Voltage
C ombi -Sense/D i rect Output Voltage
VID pi ns except VID 5
VID 5
Osci lli ator Frequency setti ng and OUT pi ns
Ground Sense
All other i nput pi n
Thermal resi stance of Juncti on to C ase
Symbol
V
CC
OS1, OS2, OS3, OS4, OUTSEN
VID 0~VID 4
VID 5
OUT1, OUT2, OUT3, OSC REF
GSENSE
OUT4, FB, D AC STEP
Θ
JC
for SOIC -24
Θ
JC
for TSSOP-24
Ambi ent T mperature Range
e
Juncti on T mperature Range
e
Storage T mperature Range
e
Lead T mperature (Solderi ng) 10 Sec.
e
T
A
T
J
T
STG
T
LEAD
Maximum
20
-0.3 to Vcc+0.3
7
Vcc+0.3
7
-0.3 to 0.3
-0.3 to Vcc+0.3
24.6
15.6
0 to 105
0 to 125
-65 to +150
260
U nits
V
V
V
V
V
V
V
°
C /W
°
C /W
°C
°C
°C
°C
Electrical Characteristics
Unless specified: V
CC
= 12V, VID=1.30V (110110,VRD10) or 1.50V (101110,VRD10), F
OSC
= 600kHz, T
A
= 27 C. See Typical Application Circuit.
o
Parameter
C hip_Supply
IC Supply Voltage
IC Supply C urrent
UVLO Ramp Up
UVLO Ramp D own
R eference Section
Bandgap Output
Source C urrent
Supply Rejecti on
Temperature Stabi li ty
VID Step
VID Step
Symbol
Test C onditions
Min
Typ
Max
U nits
V
CC
I
CC
UVLO
UVLO
Vcc Ri si ng
Vcc Falli ng
7.5
12
10
7.3
14
13
7.5
V
mA
V
V
6.4
6.5
V
BGOUT
C
BGOUT
= 4.7nF
2.945
220
2.990
300
0.5
0.5
25
12.5
3.035
330
V
µA
mV/V
%
mV
mV
V
CC
= 10.0V ~ 14.0V
0
o
C < T
A
< 85
o
C
VRM9.X, K-8, LSB
VRD /VRM10, LSB
VRD 10 ; Internal offset=-20mV
-0.5
-1
-1
+0.5
+1
+1
%
%
%
Voltage Accuracy
V
OUT
VRM9.x ; Internal offset=-20mV
K-8 ; Internal offset=+25mV
Oscillator Section
Osci llator Frequency
Osci llator Frequency Range
Temperature Stabi li ty
NOTES: 1)Guaranteed by design, not tested in production.
Specifications subject to change without notice.
F
OSC
F
OSC
R
OSC
= 309K
540
330
600
660
2800
kHz
kHz
%
0
o
C < T
A
< 85
o
C
±5
2004 Semtech Corp.
3
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SC2643VX
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified: V
CC
= 12V, VID=1.30V (110110,VRD10) or 1.50V (101110,VRD10), F
OSC
= 600kHz, T
A
= 27 C. See Typical Application Circuit.
Parameter
Voltage Error Amplifier
Input Offset Voltage
Input Bi as C urrent
Open Loop Gai n
Uni ty Gai n Bandwi dth
Slew Rate
Transconductance Gai n
C lamp Level for OC P
C lamp Level Accuracy
C urrent Sense Amplifiers
Input Offset Voltage
Input Bi as C urrent
Gai n
C MRR
Input C ommon Mode Range
Gai n Match
Bandwi dth
D roop Amplifier
Gai n
Gai n Accuracy
(1)
VID s
Input Low Voltage Threshold
Input Hi gh Voltage Threshold
Bi as C urrent
VID 5 Pull-up Voltage for VRD /VRM10
VID 5 Pull-up voltage for VRM9.X
VID 5 Pull-up voltage for K-8
3-Phase Operation
Output 4 pull up Threshold
Pow er Good
Threshold for Vcore Ri si ng
Threshold for Vcore Falli ng
Output Hi gh Leakage
Output Low Si nk
C urrent Limit Section
Shutdown Voltage
D ynamic VID Section
Si nki ng C urrent of D AC STEP
Sourci ng C urrent of D AC STEP
I
DAC_SINK
I
DAC_SOURCE
390
340
uA
uA
VID - Shut D own Threshold
550
650
750
mV
VID - Power Good Threshold
VID - Power Good Threshold
Pwrgood = V
CC
Pwrgood = 0.8V
2
250
350
575
100
400
mV
mV
nA
mA
For 3-phase operati on
3.5
4
4.5
V
[VID 0:5]
[VID 0:5]
[VID 0:4]=0V
VID 5
VID 5
VID 5
1.8
120
1.8
4
8
185
250
2.5
6
V cc
µA
V
V
V
1.2
V
G
DA
5.4
±5
V/V
%
G
CA
0 to 3V
-0.3
2
6
±3
50
10
80
3
mV
nA
V/V
dB
V
%
MHz
G
EA
V
eoMAX
-8
1V < V
ERROUT
< 4V
C
ERROUT
= 10pF
±3
25
80
10
10
0.5
4.4
+8
mV
nA
dB
MHz
V/
µs
mA/V
V
%
Symbol
Test C onditions
Min
Typ
Max
U nits
o
NOTES: 1)Guaranteed by design, not tested in production.
Specifications subject to change without notice.
2004 Semtech Corp.
4
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SC2643VX
POWER MANAGEMENT
Pin Configurations
Top View
OS3
OS2
OS1
BGOUT
ERROUT
GSENSE
FB
DACSTEP
VCC
VID4
VID3
VID2
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
OS4
OUTSEN
OUT4
OUT3
OUT2
OUT1
AG
ND
OSCREF
PG D
OO
VID5
VID0
VID1
Ordering Information
Part Number
SC2643VXSWTR
(1)
SC2643VXTSTR
(1)
SC2643VXEVB
(2)
Package
SOIC-24
TSSOP-24
Temp. Range (T
J
)
0 to 125
O
C
0 to 125
O
C
Evaluation Board
Note:
(1) Only available in tape and reel packaging. A reel contains 1000 devices
for the SOIC-24 and 2500 devices for the TSSOP-24 package.
(2) Specify SOIC-24 or TSSOP-24 package.
(3) Lead free package.
(24-Pin SOIC/TSSOP)
Pin Descriptions
Pin#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Pin Name
OS3
OS2
OS1
BGOUT
ERROUT
GSENSE
FB
DACSTEP
VCC
VID4
VID3
VID2
VID1
VID0
VID5
PGOOD
OSCREF
AGND
OUT1
OUT2
OUT3
OUT4
OUTSEN
OS4
VID LSB.
VID 1/2 LSB / VID type select. VID5 pull-up to VCC for K-8; VID5 pull-up to 5V for VRM9.X.
Pow er good.
Oscillator frequency setting.
Clean ground for analog.
PWM output1.
PWM output2.
PWM output3.
PWM output4. Connect to VCC for 3 phase operation.
Direct output sense.
Combi-Sense Current 4. Connect to OUTSEN for 2 or 3 phase operation.
5
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Pin Function
Combi-SenseCurrent 3.
Combi-Sense Current 2. Connect to OUTSEN for 2 phase operation
