TriPhase Current Mode Controller
with Power Good
POWER MANAGEMENT
Description
The SC2434, a tri-phase, current mode controller is
designed to work with Semtech smart synchronous
drivers, such as the SC1205, SC1206, and SC1207 to
provide the DC/DC converter solution for the most
demanding Microprocessor applications. Input current
sensing is used to guarantee precision phase to phase
current matching using a single sense resistor on the
input power line. This topology reduces the power loss
and complexity associated with output current sense
methods. Multi phase operation allows significant
reduction in input/output ripple while enhancing
transient response. Two or three phase operation is
selectable. The DAC step size and range are program-
mable with external components thus allowing compliance
with new and emerging VID ranges. A novel approach
implements active droop to minimize output capacitors
during load transients.
SC2434
Features
!
!
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!
!
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12V input
Input sensing current mode control
Selectable 2 or 3 phase operation
Precision, pulse by pulse phase current matching
Active drooping allows for best transient response
Programmable internal oscillator to 1.5 MHz
Programmable DAC step size/offset allows compli-
ance with VRM9.0 and VRM9.2
VID 11111 Inhibit (No CPU)
Externally programmable soft-start
0% minimum duty cycle improves transient
response
Cycle by cycle current limiting plus hiccup
Power good signal
Applications
!
Intel Pentium-4 microprocessors
!
High performance desktop systems
Typical Application Circuit
+12V_ATX
L1
R1 3m
600nH
C1
2200uF/16v
C5
4.7uF
C6
4.7uF
+12V
R2
2R2
R5
20
D1
1N4148
R4
1R
1
2
3
4
DRN PGND
TG
BG
BST
VS
CO
EN
U1
8
7
6
5
600nH
D4
1N4148
M2
R6
1
SM/R_1206
C11
C9
1nF
C12
R9
D2
C17
1uF
M3
L3
R10
1
2
3
4
DRN PGND
TG
BG
BST
VS
CO
EN
U3
8
7
6
5
1R
D5
1N4148
M4
600nH
R11
1
SM/R_1206
C23
C22
1nF
C24
1uF
+12V
R14
2R2
D3
1N4148
R16
1R
C27
1uF
M5
L4
C77
0.33uF
C28
1500uF/6.3V
C30
1500uF/6.3V
C32
1500uF/6.3V
+
2.2nF
C25
1500uF/6.3V
C26
1500uF/6.3V
+
+
C20
1500uF/6.3V
C21
1500uF/6.3V
+
1uF
+12V
C76
0.33uF
2.2nF
C14
1500uF/6.3V
C18
1500uF/6.3V
C19
1500uF/6.3V
+
C7
1500uF/6.3V
C10
1500uF/6.3V
C4
1uF
C75
M1
L2
VOUT
0.33uF
+
C2
2200uF/16v
+
C3
2200uF/16v
+
VCCVID_PWRGD(Open Collector Input)
R3
2R2
R29
100
C8
1uF
VID4
VID3
VID2
VID1
U2
VID0
1
2
+5V_ATX
+5V
3
4
5
6
R13
V_PULL_UP
5.1K
7
8
9
PWR_GOOD
10
VID4
VID3
VID2
VID1
VID0
PGIN
ERROUT
PGOUT
FB
OSCREF
VCC
BGOUT
OUT1
OUT2
OUT3
PC
AGND
OC-
OC+
DACREF
20
19
18
17
16
15
14
13
12
11
R15
1K
R_DAC
37.4K
C31
470pF
1
2
3
4
C13
10nF
C15
1uF
C16
4.7uF
Differential
Pair
SC1205
R8
NO POP
2R2
1N4148
SC1205
SC2434
C29
100nF
R_DRP
187K
C_COMP
18pF
R_COMP
75K
R_OSC
31.6K
DRN PGND
TG
BG
BST
VS
CO
EN
U4
8
7
6
5
600nH
D6
1N4148
M6
R17
1
SM/R_1206
C34
C33
1nF
2.2nF
+5V
R_OS
46.4K
R_FB
10K
R19
750
R20
1K
SC1205
C35
+
+
+
+
+
+
+
PGND
1uF
Differential
Pair
AGND
May 18, 2005
1
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SEMTECH [ SEMTECH CORPORATION ]
